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Detailed mechanism of the OH-initiated transformation of tetrabromobisphenol A (TBBPA) has been investigated by quantum chemical methods in this paper. Abstraction reactions of hydrogen atoms from the OH groups and CH 3 groups of TBBPA are the dominant pathways of the initial reactions. The produced phenolic-type radical and alkyl-type radical may transfer to 4,4′-(ethene-1,1-diyl) bis (2,6-dibromophenol), 4-acetyl-2,6-dibromophenol and 2,6-dibromobenzoquinone at high temperature. In water, major products are 2,6-dibromo- p -hydroquinone, 4-isopropylene-2,6-dibromophenol and 4-(2-hydroxyisopropyl)-2,6-dibromophenol resulting from the addition reactions. Total rate constants of the initial reaction are 1.02 × 10 −12 cm 3 molecule −1 s −1 in gas phase and 1.93 × 10 −12 cm 3 molecule −1 s −1 in water at 298 K. [ABSTRACT FROM AUTHOR]

Abstract: The reaction mechanisms of vinyl acetate with O3 are investigated by performing Density Functional Theory (DFT) calculations as an attempt to investigate the photooxidation reaction of acetate in the atmosphere. The detailed reaction mechanisms are proposed. The potential energy surface profiles (PESs) are constructed. Several products (formaldehyde, heroperoxymethyl formate and formic acetic anhydride) resulting from the gas phase reactions are identified by comparing with the experimental results. The experimentally uncertain dominant product of CH2OO is confirmed to be heroperoxymethyl formate. The experimentally unknown mechanism for the formation of formic acetic anhydride from CH3OCHOO is proposed. Rate constants of the reaction over the temperature range of 200–2000K are obtained by using Rice–Ramsperger–Kassel–Marcus (RRKM) theory based on the above PES calculations. The rate constants are independent on pressure. [Copyright &y& Elsevier]

The potential energy surface (PES) and mechanism of the reaction of allyl acetate (AAC) with O are investigated by using density functional theory (DFT) and ab initio (MP2 and CCSD(T)) methods. The kinetics and main product branching ratios over the temperature range of (200-2,000 K) and at various pressures are obtained by employing multichannel Rice-Ramsperger-Kassel-Marcus (RRKM) theory. The results show that the main products are 2-oxoethyl acetate and formaldehyde. Two channels are found for the decomposition of primary ozonides: one path is corresponding to the 2-oxoethyl acetate + CHOO formation (R1); the other channel products formaldehyde + CHC(O)OCHCHOO (R2). In the whole temperature range, R1 is calculated to be preferable and its product yield accounts for 60-77% of the total while R2 is found to contribute 20-40% to the total product yield. The overall rate constants show pressure independence and strong positive temperature dependence. [ABSTRACT FROM AUTHOR]

Abstract: The mechanism and kinetic properties of OH-initiated gas-phase reaction of 2,2′,4,4′-tetrabrominated diphenyl ether (BDE-47) have been studied at the MPWB1K/6-311+G(3df,2p)//MPWB1K/6-31G(d) level of theory. Two types of reactions including hydroxyl addition and hydrogen abstraction have been considered. The calculation results indicate that addition reactions except for the bromo-substituted addition reaction have lower energy barriers than hydrogen abstraction reactions. Hydroxyl radical is most likely to be added to non-substituted C atoms (C(3), C(5), and C(6) atoms). Moreover, for all the reactions with OH radical, the bromo-substituted C atoms encountered the highest barrier compared to that of the rest C atoms. The rate constants and product branching ratios of each pathway have been deduced over a wide range of 200–1000K using canonical variational transition state (CVT) theory with small curvature tunneling (SCT) contribution. This study can be regarded as an attempt to investigate the OH-initiated photochemical reaction mechanism of polybrominated diphenyl ethers (PBDEs). [Copyright &y& Elsevier]

This paper reports a theoretical study on the reaction of propyl vinyl ether (PVE, CH3CH2CH2OCH=CH2) with OH radicals in the presence of O2 and NOx. The reaction pathway has been studied with the density functional theory (DFT/B3LYP) at the 6-31G* level. The total energies of all geometries are corrected at the MP2/6-311+G** level. The profile of the potential energy surface was constructed. The possible channels involved in the reaction were discussed. The results show that six product pathways are energetically feasible for the degradation of PVE initiated by OH radicals in the atmosphere. The main products for this degradation reaction are propyl formate, formaldehyde, and glycolic acid propyl ester in which propyl formate and formaldehyde are mainly from the OH addition to C5 atom. [ABSTRACT FROM AUTHOR]

Abstract: The hydrolysis of N-benzyl 3-oxo-β-sultam and the general base catalysis by the neucleophile are investigated. Different possible mechanistic pathways of the reaction are proposed. Both B3LYP/6-31G* and B3LYP/6-311+G* were employed to calculate the reaction pathways. The results show that in the case of non-catalyzed hydrolysis the pathways producing N-benzyl-acylamide methyl sulfonate (P1) and N-benzyl-2-sulfonic acylamide acetic acid (P2) have very similar activation energies; they are competing reactions. However, in the case of catalyzed hydrolysis by a second water molecule, the break of C–N bond is preferred. The theoretical results are in good agreement with the recent experimental observations. [Copyright &y& Elsevier]

The effects of water and alcohol on the alcoholysis mechanisms of N-methyl-1,2-thiazetidine-1,1-dioxide and the differences of these effects have been studied using the Density Functional Theory (DFT) method at the B3LYP/6-31G* level. The results have been compared with a nonassisted study carried out previously. The results show that the water- and alcohol-assisted alcoholysis of N-methyl-1,2-thiazetidine-1,1-dioxide reduces the active energy greatly compared to the nonassisted reaction. The most favored pathway for alcoholysis of 1,2-thiazetidine-1,1-dioxides is pathway a of the stepwise reaction. The orientation of attack of CH3OH on S1 is from the more hindered side of the S1. The energy barrier of the cleavage of the C−S bond and producing N-methyl-N-ethyl-amino-methyl sulfonate (P1) is the highest among all of reaction pathways, and this may be the possible reason of having no experimental evidence on the formation of product P1. The results also show that reactions that are alcohol-assisted have a little higher energy barrier than one under water-assisted alcoholysis of N-methyl-1,2-thiazetidine-1,1-dioxide. [ABSTRACT FROM AUTHOR]

The alcoholysis of N-methyl-1,2-thiazetidine-1,1-dioxide has been investigated using ab initio and density functional theory. The geometries, energies and frequencies of reactants, intermediates, transition states and products are calculated. Our results indicate the alcoholysis of N-methyl 1,2-thiazetidine 1,1-dioxide proceeds via two reaction channels. Channel I is the cleavage of bond C–S and producing N-methyl-N-ethyl amino-methyl sulfonate (P1, in Fig. 1) in which attacking of CH3OH and breaking of bond C–S are concerted. Channel II is the cleavage of bond S–N and producing 2-(N-methyl) taurine methyl ester (P2, in Fig. 1) in which there are two reaction processes with two different mechanism: concerted and stepwise. The most favorite pathway for alcoholysis of N-methyl 1,2-thiazetidine 1,1-dioxide was found. The energy barrier of the cleavage of C–S bond and producing P1 is the highest among them. We think that this may be the possible reason of having no experimental evidence on the formation of product P1. [Copyright &y& Elsevier]

The alcoholysis of 1,2-thiazetidine 1,1-dioxide has been investigated using ab initio and density functional theory at HF/6-31G*, MP2/6-31G*//HF/6-31G* and B3LYP/6- 31G* levels. The geometries, energies and frequencies of all stationary points were calculated in detail. Solvent effects have been considered by means of a polarizable continuum model (PCM). Our results indicate the alcoholysis of 1,2-thiazetidine 1,1-dioxide proceeds via concerted mechanism and stepwise mechanism. In the stepwise mechanism, two possible reaction pathways can be followed whilst one possible reaction pathway can be followed in the concerted mechanism. The most favorite pathway for alcoholysis of 1,2-thiazetidine 1,1-dioxide was found. [Copyright &y& Elsevier]

Understanding the prolonged spatiotemporal evolution and identifying the underlying causes of Ulva prolifera green tides play pivotal roles in managing such occurrences, restoring water ecology, and fostering sustainable development in marine ecosystems. Satellite remote sensing represents the primary choice for monitoring Ulva prolifera green tides due to its capability for extensive, long-term ocean monitoring. Based on multi-source remote sensing images, ecological and environmental datasets, and machine learning algorithms, therefore, this study focused on "remote sensing modelling - evolution history - change trends - mechanism analysis" to elucidate both the remote sensing monitoring models and the underlying driving factors governing the spatiotemporal evolution of Ulva prolifera green tides in the highly impacted South Yellow Sea of China. With the use of GOCI Ⅰ/Ⅱ images, an hybrid remote sensing extraction model merging the robustness of the random forest (RF) model and the optical algae cloud index (ACI) was established to map Ulva prolifera distribution patterns. The ACI-RF method exhibited exceptional performance, with an F1 score surpassing 0.95, outperforming alternative methods such as the support vector machine (SVM) and K-nearest neighbour (KNN) methods. On the basis, we analysed the evolutionary trends and the driving factors determining these distribution patterns using meteorological data, runoff data, and data on various water quality parameters (SST, ocean current speed, wind speed, precipitation, DO, PAR, Si, NO 3 -, PO 4 3-and N/P). Over the period from 2011 to 2022, excluding 2021, there was a notable decline in the area of Ulva prolifera green tides, varying between 397 and 2689.9 km2, with an average annual reduction rate of 3%. The maximum annual biomass varied between 0.12 and 15.9 kt. Notably, more than 75% of the area of Ulva prolifera green tides exhibited northward drift, which was significantly influenced by northern currents and wind fields. The analysis of driving factors indicates that factors such as average sea surface temperature, eastward wind speed, northward wind speed, precipitation, PO 4 3- and N/P/Si significantly influence the biological growth rate of Ulva prolifera. Furthermore, coastal land use change and surface runoff, particularly surface runoff in June, significantly impacted the growth rate of Ulva prolifera, with Pearson correlation coefficients of 0.74 and 0.67, respectively. Against the background of global warming and severe deterioration in the marine environment, Ulva prolifera blooms persist. Consequently, two distinct management strategies were proposed based on the distribution patterns and cause analysis results for addressing Ulva prolifera green tides: establishing a continuous protection framework for rivers, lakes, and nearshore areas to mitigate pollutant inputs and implementing precise environmental monitoring measures in urban expansion areas and farmlands to combat overgrowth-induced green tides. This methodology could be applied in other regions affected by marine ecological disasters, and the criteria for selecting influencing factors offer a valuable reference for designing tailored and proactive measures aimed at controlling Ulva prolifera green tides. • A hybrid model of random forest and Algae Cloud Index(ACI) was developed to extract Ulva prolifera green tides. • The spatial-temporal evolutions of Ulva prolifera green tides in the South Yellow Sea from 2011 to 2022 were analyzed. • The effects of 11 natural factors and 2 human factors on the blooms of Ulva prolifera green tides were analyszed. • Surface runoff in June, nutrient input, and land use changes are three major driving factors of Ulva prolifera green tides. [ABSTRACT FROM AUTHOR]

• Summarized the initial ozonolysis rules of typical LCMs in the atmosphere. • Predicted eco-toxicity of CEB-2F and its transformation products. • Revealed the adsorption mechanism of typical LCMs on the surface of TiO 2 clusters. • Elucidated the role of TiO 2 clusters on the ozonolysis of typical LCMs. • Illustrated the long-distance transmission capability of LCMs. Mineral aerosol particles significantly impact environmental risk prediction of liquid crystal monomers (LCMs). In this work, we investigated the reaction mechanisms and kinetics of three typical LCMs (4-cyano-3,5-difluorophenyl 4-ethylbenzoate (CEB-2F), 4-cyano-3-fluorophenyl 4-ethylbenzoate (CEB-F), and 4-cyanophenyl 4-ethylbenzoate (CEB)) with ozone (O 3) in the atmospheric gas, liquid, and particle phases employing density functional theory (DFT). Here, O 3 is prone to add to the benzene ring without F atom(s) in the selected LCMs. The ozonolysis products are aldehydes, carboxylic acids, epoxides, and unsaturated hydrocarbons containing aromatic rings. Those products undergo secondary ozonolysis to generate small molecular compounds such as glyoxal, which is beneficial for generating secondary organic aerosol (SOA). Titanium dioxide (TiO 2), an essential component of mineral aerosol particles, has good adsorption properties for LCMs; however, it slightly reduces the reactivity with O 3. At 298 K, the reaction rate constant of the selected LCMs reacting with O 3 in the gas and atmospheric liquid phases is (2.74‒5.53) × 10−24 cm3/(mol·sec) and 5.58 × 10−3‒39.1 L/(mol·sec), while CEB-2F reacting with O 3 on (TiO 2) 6 cluster is 1.84 × 10−24 cm3/(mol·sec). The existence of TiO 2 clusters increases the persistence and long-distance transportability of LCMs, which enlarges the contaminated area of LCMs. [Display omitted] [ABSTRACT FROM AUTHOR]

The discovery of new and functional macrocyclic host compounds is an important part of supramolecular chemistry. Since the experimental synthesis, prism[n]arenes (Pr[n]As), a class of naphthol‐based macrocyclic arenes, have attracted much attention. In this work, from the perspective of theoretical calculation and research, Pr[n]As (n = 4 ~ 7) were studied by density functional theory (DFT) calculations and molecular dynamics (MD) simulations. The prismatic configuration isomers, electronic structures, absorption spectra, and host‐guest chemistry were discussed thoroughly. DFT calculation results showed that 1,5‐, 3,7‐, and "hybrid" 15,37‐Pr[n]As were the most representative configurations with the rigid prismatic molecular skeleton. Based on time‐dependent density functional theory (TD‐DFT), the absorption spectra of Pr[n]As were all in the range of ultraviolet light which were mainly attributed to π‐π* transitions. The molecular cavities of Pr[n]As were electron‐rich and capable of accommodating a variety of cations or electron‐conjugated molecules. MD simulation results showed that a Pr[n]A molecule was able to capture the guest molecule into its molecular cavity and maintain in the state of equilibrium in solvents. [ABSTRACT FROM AUTHOR]

Hexabromocyclododecanes (HBCDs) have been frequently detected in environment. The isomerization between HBCDs and thermodynamic properties of unimolecular and bimolecular decomposition reactions of (−)-α-HBCD and (−)-γ-HBCD have been investigated using the quantum chemical method. The results show that isomerization via 1,2-shift of Br atoms occurs between the (−)-α/(−)-γ, (+)-α/(+)-γ, and (+)-β/(−)-β counterparts of HBCDs. Self-decomposition of HBCDs to pentabromocyclododecenes and HBr progresses slowly at low temperature but becomes competitive with the isomerization reactions at high temperature. The generated products are also toxic pollutants to the aquatic organisms. The reaction of two commonly detected HBCDs, (−)-γ-HBCD and (−)-α-HBCD, with OH radical and H atom have been studied. (−)-γ-HBCD has bigger rate constants in the reaction with OH radical and H atom than (−)-α-HBCD all over studied temperature. After a series of unimolecular or bimolecular reactions, the formed pentabrominated intermediate can decompose into ethane, vinyl bromide, and 1,2-dibromoethylene after sufficient heat adsorption. [ABSTRACT FROM AUTHOR]

[Display omitted] • The lowest-energy conformations of thiapillar[5]arenes are obtained by DFT calculations. • Electronic structure analysis reveals the evolution from electronegativity to electropositivity in the molecular cavities of thiapillar[5]arenes. • Thiapillar[5]arenes are able to accommodate various guests based on the electronic complementarity and the spatial matching. • The sulfur-containing derivatizations of pillar[ n ]arenes are expected to expand the application prospects in supramolecular biology and electrochemistry related fields. The chemical modification of bridging groups of the pillar[ n ]arenes is an important way to functional derivatization and expand the application fields. So far, however, there have been few reports on this issue. On the basis of experimental reports, a series of thiapillar[5]arene structures with sulfur, sulfoxide and sulfone as bridging groups are proposed in this work. By using density functional theory (DFT) calculations, thiapillar[5]arenes are studied systematically at the ωB97XD/6-311G(d,p) level of theory. All the structures have regular pentagonal shape with the point group of D 5. The substitution of bridging methylene by sulfur leads to a significant enlargement in the molecular cavity, an extension of the spatial delocalization of the electrons, and a redshift of the absorption spectrum. The bridging groups of sulfoxide and sulfone can greatly improve the solvent effects in polar solvents, which is followed by the weakening of the pi-electron donating capacity inside the molecular cavity. Thiapillar[5]arenes have rich host–guest chemistry and can recognize a variety of guest species. Interestingly, the inclusion of thiapillar[5]arenes to ferrocene is a synergistic result of electronic and spatial effects. The sulfur-containing derivatizations of pillar[ n ]arenes are expected to expand the application prospects in supramolecular biology and electrochemistry related fields. [ABSTRACT FROM AUTHOR]

• The chelation of Zn2+, Cu2+, Ti4+ and Fe3+ enhances the deprotonation of catechol. • The •OH-mediated degradation of catechol and its metal complexes was studied. • The reactivity of metal complexes towards •OH is higher than that of H 2 Cat. • At pH 7, the acceleration effect follows the order of Ti4+ ≈ Zn2+ > Cu2+ > Fe3+. • The •OH-based AOPs could decrease the toxicity during degrading catechol. Catechol pollutants (CATPs) serving as chelating agents could coordinate with many metal ions to form various CATPs-metal complexes. Little information is available on the effects of complexation of metal ions on CATPs degradation. This work presents a systematical study of •OH-mediated degradation of catechol and catechol-metal complexes over the whole pH range in advanced oxidation processes (AOPs). Results show that the pH-dependent complexation of metal ions (Zn2+, Cu2+, Ti4+ and Fe3+) promotes the deprotonation of catechol under neutral and even acidic conditions. The radical adduct formation (RAF) reactions are both thermodynamically and kinetically favorable for all dissociation and complexation species, and OH/ O− group-containing C positions are more vulnerable to •OH attack. The kinetic results show that the complexation of the four metal ions offers a wide pH range of effectiveness for catechol degradation. At pH 7, the apparent rate constant (k app) values for different systems follow the order of catechol+Ti4+ ≈ catechol+Zn2+ > catechol+Cu2+ > catechol+Fe3+ > catechol. The mechanistic and kinetic results would greatly improve our understanding of the degradation of CATPs-metal and other organics-metal complexes in AOPs. The toxicity assessment indicates that the •OH-based AOPs have the ability for decreasing the toxicity and increasing the biodegradability during the processes of catechol degradation. [Display omitted] [ABSTRACT FROM AUTHOR]

The neutral hydrolysis mechanisms of a simple β-phospholactam with and without water-assisted reaction have been studied by using quantum chemical method at HF/6-31G**, MP2/6-31G** and B3LYP/6-31G** levels, respectively. The reaction can proceed by two different mechanisms: concerted and stepwise. There are two pathways in stepwise, i.e. pathway a and b, and the energy barriers of them are close. The energy barriers of water-assisted hydrolysis of β-phospholactam are obviously lower than those of no-water-assisted hydrolysis system. The energy barriers of stepwise mechanism are much lower than those of the concerted pathway in both cases. The solvent effects have been considered by means of a polarizable continuum model. The hydrolysis mechanism of β-phospholactam with that of the β-lactam and β-sultam was compared. [ABSTRACT FROM AUTHOR]

2,4-Dinitrophenol (DNP) as a widely used chemical is harmful to human health. Highly active free radicals-based advanced oxidation technology (AOT) has been successfully applied to degrade DNP in wastewater. This work aims to systematically and comprehensively analyse the oxidative degradation of DNP caused by eleven different oxygen-containing free radicals (HO·, SO4−· , H2PO4·, NO3·, HPO 4 − · , CO 3 − · , BrO·, ClO·, HO2·, PO 4 2 − · , and O 2 − · ) involved in wastewater treatment. The quantum chemical methods are used to clarify thermodynamic feasibility, favourable site, and characteristics of reactions between different oxygen-containing free radicals and DNP based on three reaction mechanisms of free radical addition, hydrogen atom abstraction, and single electron transfer. The DNP degradation initiated by H2PO4·/NO3·/HO· is relatively easy to proceed. The kinetic data of the above reactions assist the thermodynamic analysis results. Particularly, the reaction pathways of complete degradation process of HO· and DNP are proposed. The production paths of main intermediates/products detected in the experiments are determined. The total rate constant of HO· and DNP is calculated to be 1.23×108 M-1s-1. The ecotoxicity evaluation suggests most intermediates/products is decreased during degradation, and a small part of by-products are still toxic. In addition, some insights into the AOT treatment of wastewater containing DNP are provided. [ABSTRACT FROM AUTHOR]

Adjusting pH values in aqueous environments can significantly improve the efficiency by which parabens and halo-parabens are removed. In this study, 20 neutral and deprotonated species were selected as models to investigate their pH-dependent removal mechanisms and kinetics by a UV/H 2 O 2 process using density functional theory (DFT). Compared to neutral species, deprotonated species exhibit higher reactivity to HO• due to their high electron cloud density. H atom abstraction (HAA) reactions on the substitution groups are the most favorable pathways for neutral species, while radical adduct formation (RAF) reactions are the most favorable for deprotonated species. Single electron transfer (SET) reactions can be neglected for neutral species, while these reactions become a viable route for deprotonated molecules. The total reaction rate constants range from 1.63 × 109 to 3.74 × 1010 M− 1 s− 1 at pH 7.0, confirming the experimental results. Neutral and weakly alkaline conditions are favorable for the degradation of MeP and halo-parabens in the UV/H 2 O 2 process. The order of removal efficiency at optimum pH is dihalo-parabens > mono-halo-parabens ≈ F, F-MeP > MeP. Furthermore, the transformation products must undergo oxidative degradation due to their high toxicity. Our findings provide new insights into the removal of parabens and their halogenated derivatives from wastewater. [Display omitted] • The relationship between pH and reaction mechanisms was revealed. • Neutral and weakly alkaline conditions are favorable for degradation. • The removal of mixed species was more difficult than single species. • The toxicity of transformation products to aquatic organisms was assessed. [ABSTRACT FROM AUTHOR]

Halogenated α, β-unsaturated C 4 -dicarbonyl (X-BDA), a novel family of high-toxicity ring cleavage products, is produced during the disinfection of phenolic compounds. The technique of electrocatalytic hydrodehalogenation (ECH) is efficient in rupturing carbon-halogen bonds and generating useful chemicals. This study used first principles to examine the ECH reaction mechanism of X-BDA and the subsequent hydrogenation reaction of the toxic derivative BDA over the 1 T′-MoS 2 /Ti 3 C 2 T 2 (T = O, OH, F) catalysts. The catalytic activity of Ti 3 C 2 T 2 (T = O, OH, F) catalysts decreases gradually with -OH, -F, -O functional group. The loading of 1 T′-MoS 2 onto the Ti 3 C 2 T 2 surface improves the stability and selectivity of Ti 3 C 2 T 2. In particular, 1 T′-MoS 2 /Ti 3 C 2 (OH) 2 is most conducive to the ECH reaction of X-BDA via a direct-indirect continuous reduction process. It exhibits excellent removal capability towards Cl-BDA, with decreasing reactivity in the order of the Cl-, Br-, and I-BDA. The material offers a solution to the challenging dechlorination issue. The dehalogenated product BDA can be hydrogenated to produce 1,4-butanedial, 1,4-butanediol, and 1,4-butenediol. Three valuable chemicals can be obtained by exerting an applied potential of − 0.65 V. This work suggests that the formation of heterojunction catalyst may lead to new strategies to improve ECH for environmental remediation applications. [Display omitted] • 1 T′-MoS2 loading significantly improved the stability and activity of Ti3C2T2 catalyst. • 1 T′-MoS2/Ti3C2(OH)2 is an excellent surface material for X-BDA hydrodechlorination reaction. • 1 T′-MoS2/ Ti3C2(OH)2 has stronger catalytic activity for Cl-BDA than Br-BDA and I-BDA. • BDA continues hydrogenation to generate valuable chemicals. [ABSTRACT FROM AUTHOR]

In this work, sixteen typical chlorinated and brominated aromatic disinfection by-products (DBPs) were selected as examples to investigate their different degradation mechanisms initiated by HO• and SO 4 •-. Addition reactions were the main mode of degradation of DBPs by HO•, while SO 4 •- dominated H-abstraction reactions and single electron transfer reactions. Chlorinated compounds had higher reactivity than brominated compounds. Furthermore, substituents with stronger electron-donating effects promoted the electrophilic reaction of DBPs with the two radicals. In addition, we developed a model based on the chemical properties LUMO, f max − , and hardness for predicting the average reaction energy barriers for the initial reactions of DBPs with HO• and SO 4 •-. The model had good predictive performance for the difficulty of degradation of different DPBs by HO• and SO 4 •-, with R2 values of 0.85 and 0.87, respectively. Through the degradation efficiency simulation, we found that longer reaction times, higher oxidant concentrations and lower pollutant concentrations were more favorable for the removal of DBPs. The UV/PDS process showed better degradation of DBPs than the UV/H 2 O 2 process. In addition, most degradation products of DBPs exhibited less toxicity to aquatic organisms than their parent compounds. This study provided theoretical guidance for the degradation and removal of other aromatic DBPs at the molecular level. [Display omitted] • The initial degradation mechanisms of 16 emerging aromatic DBPs were investigated for the first time. • Comparison of different degradation modes of DBPs by hydroxyl radicals and sulfate radicals. • The effects of different electron-donating and electron-absorbing groups on the reaction mechanisms were analyzed. • A model for simulating the average reaction energy barrier with various chemical descriptors has been established. • The toxicological information for 16 emerging aromatic DBPs was predicted. [ABSTRACT FROM AUTHOR]

The reactions between chlorobenzene(CB) and ozone have been studied comprehensively in this paper. Chlorobenzene is a commonly found chlorinated aromatic volatile organic compound(VOC), and its emission into the atmosphere can cause harm to the ecosystem and human health. The frequent occurrence of mineral particles from sandstorms exerts a significant influence on the atmospheric chemistry of the troposphere. Mineral particles are abundant in SiO 2 and Al 2 O 3 content. Therefore, we investigated the homogeneous and heterogeneous reaction processes of CB and ozone in the atmosphere by using density functional theory (DFT) method at the M06-2X/6–311++g(3df,2p)//M06-2X/6–31+g(d,p) level. The atmospheric fate, reaction rate and toxicity evaluation of CB ozonation were studied in the gas-phase section. Toxicity evaluation results showed that ozonation of CB could effectively reduce its toxicity. For the heterogeneous process, we simulated three types of SiO 2 clusters and nine types of (Al 2 O 3)n clusters, and studied the configurations of CB adsorbed on the cluster surfaces. We found that adsorption of CB on the SiO 2 clusters was achieved through hydrogen bonding, while adsorption of CB on the Al 2 O 3 clusters was achieved through both hydrogen bonding and metal bonding. The energy for CB adsorption on the (Al 2 O 3)n cluster surface was higher than that for the Si x O y (OH) z cluster surface, and both types of clusters exhibited efficient adsorption of CB. As the Si x O y (OH) z clusters grew larger, the rates for the reactions between O 3 and CB increased. CB travelled long distances along the Al 2 O 3 clusters, leading to an extended influence range. [Display omitted] • The reaction mechanism of CB reacting with O 3 in homogeneous and heterogeneous were studied. • Toxicity assessment showed that ozonolysis effectively reduced the ecotoxicity. • The Al 2 O 3 clusters have a stronger adsorption effect on CB compared to the SiO 2 clusters. • The environmental risks may increase due to the promotion of Al 2 O 3 to the studied reactions. [ABSTRACT FROM AUTHOR]

Quinone-based macrocyclic compounds have been proposed as promising electrode materials for rechargeable lithium-ion batteries (LIBs). To improve the electrochemical performance, in this paper, two heteroatom-bridged pillar[4]quinones (namely, oxa- and thia-pillar[4]quinones) are presented as active cathode materials for LIBs. The geometry structures, electronic structural properties, and electrochemical properties of these new species are calculated by Density Functional Theory (DFT) at the M06-2X/6-31G(d,p) level of theory. Two heteroatom-bridged pillar[4]quinones possess higher theoretical specific capacity (659 mA h g−1 and 582 mA h g−1 for oxa- and thia- pillar[4]quinones, respectively) than that of parental pillar[4]quinone (446 mA h g−1). The electrochemical performances of oxa- and thia-pillar[4]quinones are predicted theoretically to be superior to those of pillar[4]quinone as cathode material for LIBs. Compared with oxa-pillar[4]quinone, thia-pillar[4]quinone is predicted to be slightly more suitable as cathode electrode material. These results may provide fresh ideas and guidelines for enhancing the performance of quinones organic electrode materials for LIBs. Two heteroatom-bridged pillar[4]quinones, Oxapillar[4]quinone and Thiapillar[4]quinone, are proposed as the electrode active molecules. The lithium storage mechanisms and electrochemical properties are investigated by using DFT calculations. The results show that the heteroatom-bridged pillar[4]quinones are predicted theoretically to exihibit a better electrode material performance than the parent pillar[4]quinone. [ABSTRACT FROM AUTHOR]

A theoretical investigation on oxidation reaction of ethyl vinyl ether (EVE) and.Cl are carried out in this paper. By employing M06-2x/6-31 + g(d,p)//6-311++g(3df,2p) method, complex reaction mechanisms are assumed on the basis of thermodynamic data. All the.Cl-addition reactions are dominant channels. The corresponding major products, such as ethyl formate, acetaldehyde and several chloro compounds, are generated from.Cl-addition to double bond of EVE. These products play an important role in the formation of secondary organic aerosol. By employing MESMER grogram, rate coefficients of the primary reactions are computed in the temperature range of 200–400 K and the pressure range of 500–2000 Torr. Combined with the kinetic data and temperature, an Arrhenius equation is fitted as kEVE+Cl = 1.54 × 10−10 exp (121.9/T). Also, the rate constant at 298 K and 760 Torr is calculated to be 2.17 × 10−10 cm3 molecule−1 s−1. Furthermore, the atmospheric lifetime of EVE with respect to.Cl is estimated to be 4.3–11.9 h in different regions. The short lifetime indicates that ·Cl-initiated oxidation is competitive in the degradation of EVE in some special areas. This work could confirm the experimental investigation and serve as the supplement of our previous theoretical studies. [ABSTRACT FROM AUTHOR]

In this paper, the heteroatom-bridged pillar[n]arene derivatives, namely bora-, aza-, and oxa-pillar[n]arenes (PnX, X = B, N, and O respectively, n = 4 − 6) are studied by quantum chemical calculations at the ωB97XD/6-311G(d,p) level of theory. The geometries, energetics, electronic structures, absorption spectra, solvent effects, and the inclusion complexation with paraquat dication are discussed in detail. The calculated results show the structures of pentamers (P5X) are more stable compared with tetramers (P4X) and hexamers (P6X) and the PnB have relatively loose and irregular geometry structures. The molecular cavities of PnX are electron-rich and capable of accommodating cationic guests. Absorption spectra of PnN and PnO are very similar to those of Pn with one intense peak (λmax) at around 260 nm, while PnB indicates another characteristic peak between 300 and 400 nm. P5X can form inclusion complexes of 1:1 stoichiometry with paraquat dication, and P5N exhibits strongest combination ability with paraquat dication among them. These thorough understanding of the structure and properties of heteropillar[n]arenes will broaden the designs, syntheses, and applications of pillararenes. [ABSTRACT FROM AUTHOR]

• We used theoretical methods to discuss reactions of 4-chloroguaiacol with OH onto catalyst. • Carbon-doped BN nanosheet has outstanding adsorption and catalytic performance. • Carbon-doped BN nanosheet may be a promising photocatalyst for organic removal. • The transformation products of 4-chloroguaiacol are still harmful to aquatic environment. Although carbon-doped BN nanosheet (BCN) has been successfully synthesized and used, it has not been reported as a photocatalyst for the degradation of organic pollutants. In this study, 4-chloroguaiacol (4-CG) was selected as a representative substance to investigate the potential of utilizing BCN as photocatalyst for organic removal by use of computational simulation. The adsorption mechanisms, degradation mechanisms, and kinetics of 4-CG with the presence of different catalysts were determined. The adsorption energy of 4-CG on BCN was 10.71 kcal mol−1, and the Δ G ≠s of initial reactions of 4-CG with OH were also reduced onto the BCN substrate. The band gap of BCN was 1.54 eV. Our computations depicted that the doping of aromatic carbon into BN narrows bandgap, and retains well catalytic performance and adsorption properties. Therefore, BCN nanosheet is a promising photocatalyst for organic pollutants removal. Possible degradation pathways of 4-CG and aquatic toxicity assessment during degradation were also carried out. More toxic products would be formed and the transformation products were still harmful to three trophic levels of aquatic organisms (fish, green algae, and daphnia). [ABSTRACT FROM AUTHOR]

• The first step of SO 4 · - / · OH -initiated reactions on 19 POCs was studied. • Δ G SET ≠ is negatively correlated with electron-donating effect of substituents. • The OH-initiated RAF reactions at site 4/6 and HAA reactions on substituents are favorable. • k total and ecotoxicity were calculated. Phenolic organic contaminants (POCs) in water environment have been usually degraded by advanced oxidation processes (AOPs) based on sulfate radicals (SO 4 · - ) and hydroxyl radicals (OH). In this paper, the first step of SO 4 · - / · OH -initiated oxidation reactions toward 19 POCs were investigated using density functional theory (DFT) in order to explore and compare the reactivity of POCs with two free radicals in the aqueous phase. The oxidation reactions initiated by SO 4 · - / · OH were confirmed that POCs can follow three reaction mechanisms: radical adduct formation (RAF), hydrogen atom abstraction (HAA), and single electron transfer (SET). The rate constants of all primary oxidation reactions were calculated using transition state theory (TST). The results turn out that the stronger the electron donating effects of the substituent on POCs, the better the reactivity of POCs with two free radicals. SET mechanisms are main reaction pathways for SO 4 · - -initiated oxidation reactions. Furthermore, the ecotoxicity assessment shows that most OH adducts have higher toxic on aquatic organisms than corresponding reactants. For all the POCs covering in this work, the order of acute toxicity is p-DP > o-AP > m-AP (p-AP) > MP > CP > NP > m-DP (o-DP) > phenol > YP, while the chronic toxicity is in the order p-DP > o-AP > m-AP (p-AP) > MP > CP > NP > YP > phenol > m-DP (o-DP). Thus, the application of AOPs for the removal of POCs should be taken seriously. [ABSTRACT FROM AUTHOR]

The OH-initiated transformation mechanisms, kinetics and ecotoxicity assessment of guaiacol (2-methoxyphenol) in the presence of O 2 /NO x were investigated both in atmosphere and wastewater. The solvent effect lowers the energy barriers of initial OH-addition reactions more than H-abstraction reactions, leading to much higher addition branching ratio (Γ add) of 0.92 in aqueous solution than that of 0.42 in gas-phase. At 298 K, the overall rate constants of the title reactions in atmosphere and wastewater are 5.56 × 10−12 and 1.41 × 10−11 cm3 molecule−1 s−1 with corresponding half-lives of 34.6 h and 0.82 s, respectively. In atmosphere, all the proposed favorable products including nitroguaiacols, methoxybenzoquinone, 2-hydroxyphenyl formate, 2-methoxybenzene-1, 3-diol and dialdehyde could contribute to secondary organic aerosols (SOAs). In wastewater, NO 2 addition reactions lead to higher toxicity of products (nitroguaiacols and 2-methoxybenzene-1, 4-diol) than that of parental guaiacol. However, O 2 /NO addition pathways may generate less harmful products except for methoxybenzoquinone (P3) which is with higher toxicity than guaiacol. Therefore, more attention should be focused on the products formed from OH-initiated reactions of guaiacol both in atmosphere and wastewater. Unlabelled Image • Firstly studied radicals-initiated reactions of MPs in aqueous-phase theoretically • The solvent effect leads to much higher Γ add of 0.92 than 0.42 in gas-phase. • The rate constants and half-life for hydroxylation of guaiacol were calculated. • Favorable products proposed in the atmosphere contribute to SOAs. • Most products are less toxic formed from O 2 /NO addition than NO 2 addition. [ABSTRACT FROM AUTHOR]

• Defective UiO-66-NH 2 -supported ion imprinted polymers were developed. • The G-IIP-3 exhibits excellent adsorption capacity and selectivity for Gd(III). • 2-hydroxyphosphonoacetic acid was used as the functional monomer and defective linker. • The phosphate groups and Zr-O clusters contribution to the Gd(III) adsorption on G-IIP-3. Developing a high-performance adsorbent for the recovery of Gd(III) from wastewater is of great environmental and economic significance. Metal organic frameworks (MOFs) functionalized with mixed-linker defect strategy hold huge potential for use as adsorbents for removing heavy metal ions from wastewater. However, the defective MOFs still show a relative low selectivity to target metal ions. Herein, we propose the combination of surface-imprinting and defect engineering strategies to synthesize Gd(III) ion-imprinted polymers (G-IIPs) based on mixed-linker Zr-MOFs, and apply them for capturing Gd(III) ions from wastewater. It is worth noting that 2-hydroxyphosphonoacetic acid not only served as monodentate ligand to in-situ induce ligand vacancies and form hierarchical pores on UiO-66-NH 2 , but also as high-efficient functional monomer in imprinted layer to provide the strong coordination ability towards Gd(III). Benefiting from its abundant binding sites and hierarchical pore structure, the as-prepared G-IIP-3 with rich defects displays a high adsorption capacity of 181.75 mg·g−1 and a short equilibration time of 30 min for Gd(III). In addition, G-IIP-3 presents highly selective capture of Gd(III) over interfering ions. Furthermore, density functional theory calculation demonstrates that both phosphate group and Zr-O cluster play key roles in the Gd(III) adsorption process. Thus, this work provides an effective method to develop high-performance materials for Gd(III) recovery by organically combining the advantages of surface-imprinting and defect engineering strategies. [ABSTRACT FROM AUTHOR]

[Display omitted] • The sandstorms presented a trend of decreasing first and then increasing. • The sandstorms mainly occurred in spring (92.4%) and winter (5.6%). • Hot spots of sandstorms were concentrated in the Loess Plateau and desert area. • In the future, sandstorm will become more frequent, in line with past trends. Sandstorm, as a disastrous weather phenomenon, seriously threatens the ecological environment and human health. In this study, the normalized brightness temperature dust index (NBTDI) data set of sandstorms in Yellow River Basin, China during 2000–2021 was constructed. Based on this, the temporal and spatial distribution pattern of sandstorms in the Yellow River Basin in the 21st century was analyzed. The variation trend of NBTDI in the past 22 years was discussed. The results showed that the interannual variation of sandstorms in the 21st century weakened first and then intensified. From the perspective of seasonal variation, sandstorm events occurred most frequently in spring (92.4%), followed by winter (5.6%), and occasionally in summer and autumn. In space, the distribution of sandstorms in the Yellow River Basin had obvious spatial heterogeneity. The central location of the sandstorm in the Yellow River Basin moved slightly to the north, but all of them were concentrated on desert areas. This was caused by the combination of unique geographical location and meteorological factors. The natural climate was closely related to the occurrence of sandstorms. The variation trend of long time-series NBTDI indicated that there were long memories between 22 years of sandstorms. NBTDI had an increasing trend in the long time series. In the future, sandstorms will become more frequent, in line with past trends. This study provides important data support for comprehensive understanding of extreme sandstorm weather, and has important significance for large-scale and long-term monitoring of sandstorm weather. [ABSTRACT FROM AUTHOR]

Degradation of Chlorine-containing disinfection by-products(Cl-DBPs) on surface by electrocatalytic hydrodechlorination (EHDC) is considered a promising advanced water treatment method. Cl-DBPs have ecological toxicity and health risks so that it is urgent to degrade DBPs. We designed and verified the degradation performance of the EHDC of 18 kinds of DBPs (TAAs, TANs, TALs, TNMs, TAcAms, THMs) with different substituents led by the Ti 3 C 2 X 2 (X = O/OH) system by the first-principles. On the surface of Ti 3 C 2 (OH) 2 , DBPs react with atomic hydrogen (*H) by a direct-indirect continuous reduction mechanism to eliminate the Cl atom in turn. Dissociative adsorption of DBPs on the surface of Ti 3 C 2 (OH) 2 simultaneously realizes the first electron transfer step and forms H vacancy, which makes its electrocatalytic activity superior to that of Ti 3 C 2 O 2. Removing the six types of DBPs only needs to add −0.1 V of applied potential. In addition, we investigated the impact of substituents and chlorination degree on the reactivity of DBPs removal. The strong electron-withdrawing group is more conducive to the dechlorination reaction. Dehalogenation is much favorable in thermodynamics as the increase in chlorination degree. This study provides important insights and efficient catalysts for the degradation of DBPs and shows the potential of MXenes in eliminating chloride in water. [Display omitted] • The degradation performance of Ti 3 C 2 (OH) 2 is superior to Ti 3 C 2 O 2. • Cl atom was removed in Ti 3 C 2 (OH) 2 by direct-indirect continuous reaction. • The high activity results from H vacancy formation and synchronous first electron transfer. • Substituents effect and chlorination degree affect the reaction activity. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A theoretical study for O 3 -initiated degradation of 3-MC and 4-MC was performed. • Six addition pathways are included in the primary ozonation. • The total rate constants of ozonation for 3-MC and 4-MC were calculated. • The order of reactivity with ozone is 3-MC > 4-MC > catechol > methoxybenzene. • By ecotoxicity assessment calculations, major products are proved to be harmless. Abstract Lignin pyrolysis products that generated by biomass burning can conduce to the formation of secondary organic aerosols (SOA), especially in municipal environments. 3-Methylcatechol (3-MC) and 4-Methylcatechol (4-MC) were selected as a representative congener of lignin pyrolysis product to investigate its fate both in the atmosphere and in aqueous particles. This work aims to summarize the reaction rules of this kind of compound, evaluate the contribution of such previously unconsidered reactions to the SOA formation from methylcatechols, and to provide a solution for the optimization of the water environment of such pollutants. We performed quantum chemical calculations for the O 3 -initiated oxidative degradation of methylcatechols, including six addition reaction pathways and the further reactions of the Criegee intermediates (generated during the primary reaction) with NO (only in the gas phase), H 2 O and O 2. Using kinetic simulation, the calculated total rate constant (at 298 K and 1 atm) of O 3 -initiated reactions of 3-MC and 4-MC are 7.89 × 10−17 and 1.11 × 10−17 cm3 molecule−1 s−1. For the lignin pyrolysis products in this work and our previous studies, atmospheric lifetime comparison shows that the reactivity of these compounds takes the order 3-methylcatechol > 4-methylcatechol > catechol > methoxybenzene, which is consistent with experimental results. The ecotoxicity assessment shows majority of the toxic intermediates and intermediate products are converted into harmless compounds after ozone addition reactions. [ABSTRACT FROM AUTHOR]

In this work, the hydroxylation mechanisms and kinetics of some emerging disinfection byproducts (DBPs) have been systematically investigated through theoretical calculation methods. Five chlorophenols and eleven halogenated pyridinols were chosen as the model compounds to study their pH-dependent reaction laws in UV/H 2 O 2 system. For the reactions of HO• with 37 different dissociation forms, radical adduct formation (RAF) was the main reaction pathway, and the reactivity decreased with the increase of halogenation degree. The k app values (at 298 K) increased with the increase of pH from 0 to 10, and decreased with the increase of pH from 10 to 14. Compared with phenol, the larger the chlorination degree in chlorophenols was, the stronger the pH sensitivity of the k app values; compared with chlorophenols, the pH sensitivity in halogenated pyridinols was further enhanced. As the pH increased from 2 to 10.5, the degradation efficiency increased at first and then decreased. With the increase of halogenation degree, the degradation efficiency range increased, the pH sensitivity increased, the optimal degradation efficiency slightly increased, and the optimal degradation pH value decreased. The ecotoxicity and bioaccumulation of most hydroxylated products were lower than their parental compounds. These findings provided meaningful insights into the strong pH-dependent hydroxylation of emerging DBPs on molecular level. [Display omitted] • The pH-dependent degradation of HA-DBPs in UVH 2 O 2 system was elucidated. • The reactivity of HA-DBPs with HO• was positively pH-dependent. • The larger the halogenation degree was, the stronger the pH sensitivity of k app. • The optimal degradation pH value decreased with the increase of halogenation degree. • The hydroxylation reaction could decrease the risk of HA-DBPs. [ABSTRACT FROM AUTHOR]

• The homogenous and hybrid configurational isomers of pagoda[ n ]arenes are proposed and obtained by DFT calculations. • Electronic structure analysis reveals the π-electron rich nature within molecular cavity of pagoda[ n ]arenes. • Pagoda[ n ]arenes are able to accommodate various electron-deficient or organic conjugated guests besides cations. Studies on the synthesis, characterization, and applications of new macrocyclic host species have greatly promoted the development of supramolecular chemistry. Recently, pagoda[ n ]arenes (Pa[ n ]As), a class of anthracene-based macrocyclic arenes, were reported by Chen's group. Pa[ n ]As are inherently endowed with many fascinating properties. In order to fully understand Pa[ n ]As and expand their potential applications, the structures, properties, and supramolecular chemistry of Pa[ n ]As are systematically studied by using a computational approach. Based on density functional theory (DFT) calculations, nine homogenous Pa[ n ]As (n = 4∼6) and six hybrid Pa[4]As are discussed in detail because of their rigid pagoda molecular frameworks and their lower energies. The frontier molecular orbitals and electrostatic potential maps reveal the nature of their electronic structures. Correspondingly, UV–vis spectra are predicted by time-dependent (TD)-DFT calculations. Moreover, Pa[ n ]A molecules are capable of forming host‒guest complexes and self‒assemblies by noncovalent interactions. H-bonding, ion···pi, C H···pi, and van der Waals (vdW) interactions are addressed with the reduced density gradient (RDG) analysis. Finally, molecular dynamics (MD) simulations in the solvent show that Pa[ n ]As are able to recognize guests and maintain a dynamic equilibrium in the form of host-guest complexes. [Display omitted] [ABSTRACT FROM AUTHOR]

Assembly structure of Mn 1-x Ni x Fe 2 O 4 (0 < x < 1) nanoparticles has been adjusted by introducing polyethylene glycol (PEG) into the synthesis procedure. Colloidal nanocrystal assembly (CNA) of Mn 0.5 Ni 0.5 Fe 2 O 4 (M1N1-PEG) with inverse spinel structure can be formed with the assistance of PEG, whereas other CNAs of Mn 1-x Ni x Fe 2 O 4 (0 < x < 1) with normal spinel structures are formed no matter PEG is added or not. The structural evolution of M 1-x Ni x Fe 2 O 4 CNAs can be confirmed by the Raman spectroscopy and magnetic measurements as well as the theoretical simulation. Inverse spinel M1N1-PEG and NiFe 2 O 4 CNAs only display an electrocatalytic peak toward the oxidation of L-histidine with high sensitivity in aqueous sodium sulfate electrolyte. While all the Mn 1-x Ni x Fe 2 O 4 CNAs (0 ≤ x < 1) with normal spinel structure demonstrated the intercalation/deintercalation of sodium ions except for the inverse spinel structured M1N1-PEG. [ABSTRACT FROM AUTHOR]

The comprehensive and reasonable mechanisms of Cl-initiated oxidation of ethyl acrylate (EA) have been proposed by computing at the M06-2X/6-311++G(3df, 2p)//M06-2X/6-31+G(d, p) level of theory. The primary reaction includes eight channels: two Cl additions and six H abstractions. Comparing all calculated results, the reactions of Cl addition are easier to occur than those of H abstraction. However, the hydrogen abstraction from the -CH and -CH groups cannot be ignored. Based on the Rice-Ramsperger-Kassel-Marcus (RRKM) theory, the rate constants are determined employing the MESMER program. The calculated total rate constant (at 298 K and 760 Torr) is 1.80 × 10 cm molecule s and shows negative dependence on temperature in the range of 198-648 K. The rate constants for Cl atoms of methyl acrylate (MA), EA, methyl methacrylate (MMA), and allyl acetate (AAC) are k > k > k > k . The atmospheric lifetime of EA is 154.3 h for Cl-initiated oxidation which is compared with that of the reaction of other oxidants (OH radicals, O molecules, and NO radicals) with EA. [ABSTRACT FROM AUTHOR]

[Display omitted] • TM-Ti 3 C 2 O 2 has thermal and chemical stability. • TM-Ti 3 C 2 O 2 is selective to the products produced by CO 2 reduction hydrogenation reaction. • Co-Ti 3 C 2 O 2 has the best catalytic performance for CH 4 production. • Linear relationship between the dependence of U L affinity on *CO, *HCOOH and *OH in the basic steps of CO 2 RR mechanism. Electrocatalytic CO 2 reduction reaction (CO 2 RR) can transform CO 2 into high-value-added chemicals, which is a key step toward alleviating greenhouse gas emissions and achieving carbon neutrality. Therefore, we constructed a transition metal single-atom catalyst anchored on Ti 3 C 2 O 2 (TM-Ti 3 C 2 O 2) through theoretical calculation. The results show that TMs are stable and capable of activating CO 2. The embedding of TM breaks the symmetry of Ti 3 C 2 O 2 , causing different degrees of charge distribution of TM and distinct selectivity to CH 4 products. Co-Ti 3 C 2 O 2 is the optimum candidate for producing CH 4 with limiting potential of −0.21 V. We established a linear relationship between the activity descriptor and the limiting potential of the product, which provided a method for screening efficient TMs. With applied potential, Co, Sc, and V-Ti 3 C 2 O 2 exhibited great advantages in the CO 2 RR to CH 4. This research serves as a point of reference for industrial production and helps to achieve the objective of carbon peaking more efficiently. [ABSTRACT FROM AUTHOR]

Herbicide residues in the environment threaten high-quality agriculture and human health. Consequently, in situ remediation of herbicide contamination is vital. We synthesized a novel self-catalyzed nanozyme, ultrasmall (2–3 nm) copper peroxide nanodots modified by citric acid (CP@CA) for this purpose, which can break down into H 2 O 2 and Cu2+ in water or soil. Ubiquitous glutathione reduces Cu2+ into Cu+, which promotes the decomposition of H 2 O 2 into •OH through a Fenton-like reaction under mild acid conditions created by the presence of citric acid. The generated •OH efficiently degrade nicosulfuron in water and soil, and the maximum degradation efficiency could be achieved at 97.58% in water at 56 min. The possible degradation mechanisms of nicosulfuron were proposed through the 25 intermediates detected. The overall ecotoxicity of the nicosulfuron system was significantly reduced after CP@CA treatment. Furthermore, CP@CA had little impact on active components of soil bacterial community. Moreover, CP@CA nanozyme could effectively remove seven other sulfonylurea herbicides from the water. In this paper, a high-efficiency method for herbicide degradation was proposed, which provides a new reference for the in situ remediation of herbicide pollution. [Display omitted] • Novel copper peroxide nanodots modified by citric acid nanozymes were synthesized. • Testing showed that the nanozymes degrade herbicides by Fenton-like reactions. • The nanozymes successfully performed in-situ remediation of herbicide pollution. • Main products and pathways of nicosulfuron were identified by DFT and UPLC-TOF-MS. • The nanozymes had little impact on active components of soil bacterial community. [ABSTRACT FROM AUTHOR]

Recent research revealed inhibition or enhancement of dissolved organic matter (DOM) to the degradation of trace organic contaminants (TrOC) in natural and engineered water systems. Phenols containing acetyl, carboxyl, formyl, hydroxy, and methoxy groups were selected as the model DOM to quantitatively study their roles in the degradation of simple anilines, sulfonamide antibiotics, phenylurea pesticides by sulfate radicals (SO 4 •−). Experimental results found that p -methoxyphenol inhibited aniline and sulfamethoxazole degradation by thermally activated peroxydisulfate (TAP), while p -acetylphenol slightly promoted aniline degradation. Quantum chemical calculations were applied to study the microscopic mechanism and kinetics of phenols affecting the degradation of aniline pollutants (AN) in three ways: competitively reacting with SO 4 •−, repairing aniline cationic radicals (AN•+) and phenylaminyl radicals (AN(-H)•), and generating phenoxy radicals to degrade anilines. Generally, the degradation of sulfonamides and phenylureas prefer to be inhibited by hydroxy- and methoxy-phenols with low oxidation potential (E ox), due to their diffusion-limiting reaction with SO 4 •− and rapid back-reduction AN•+ with the calculated rate constants of (0.02 − 6.38) × 109 M−1 s−1. Phenols repairing AN(-H)• through H abstraction reaction is speculated to possibly dominate the joint degradation of phenols and anilines by TAP, which has a poor correlation with E ox. This study provides mechanistic insight into the chemical behavior of complex and heterogeneous DOM in complex aqueous environments. [Display omitted] • The effect of phenols as the model of DOM on the degradation of anilines was studied. • Primary products of anilines and SO 4 ·− are phenylaminyl and aniline cationic radicals. • Phenols can reduce phenylaminyl and aniline cationic radicals back to anilines. • Phenoxy radicals with electron-poor groups prefer to degrade electron-rich anilines. • The inhibition of aniline degradation by phenols was investigated experimentally. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cationic radicals can be repaired through single electron transfer reactions. • Reduction rate constants of a cationic radical are related to oxidation potentials. • Nitrogen-center radicals can be repaired through H atom abstraction reactions. • The self-inhibition of N -heterocyclic pollutants was proposed under PS-AOPs. • Adenine inhibits uracil degradation in the adenine-uracil mixture system. Although the inhibitory effect of purines and phenols on the degradation of N -heterocyclic compounds under UV/peroxymonosulfate (PMS) has been reported, the understanding of contaminants' underlying mechanisms and kinetics is still very limited. In this study, five omnipresent nitrogenous bases (adenine, guanine, cytosine, thymine, and uracil) in the aquatic environment were used to study the inhibitory effect of N -heterocyclic compounds under UV/PMS by quantum chemical calculations. We found that HO• and SO 4 •− initiate base degradation with second-order rate constants of (0.11 – 15.6) × 109 M−1 s−1 and (7.25 – 13.5) × 109 M−1 s−1, respectively, and the primary products contain hydroxyl derivatives (HO-P), intermediate radicals (P(-H)•) and cationic radicals (P•+, only for purines). Because of the lower oxidation potentials of HO-P than their parent compounds (P), we first proposed a self-inhibition pathway in which HO-P can revert P(-H)• and P•+ back to P through H atom abstraction and single electron transfer reactions, respectively. A more significant self-inhibition was found in the degradation of uracil than that of adenine under UV/PMS because the former has a higher yield of hydroxylated derivatives. The main hydroxylated product (6-HO-U) of uracil repairs the uracil radical (U(-4H)•) at the reaction rate constants of 1.01 × 109 M−1 s−1. The combined degradation of bases showed that the reduction rate constants of purine cationic radicals have a linear relationship with the oxidation potentials of reductants. In the adenine-uracil mixture system, adenine inhibits uracil degradation by repairing U(-4H)• (2.33 × 105 M−1 s−1). This work revealed the mechanisms and kinetics of self-inhibition and joint-degradation of N -heterocyclic compounds, which is of great significance for understanding the collective removal of contaminants in the real water environment. [ABSTRACT FROM AUTHOR]

N , N -diethyl-3-methylbenzamide (DEET), as a widely used insect repellent, is frequently detected in the environment. UV/H 2 O 2 is a valid technology to remove trace contaminants by generating hydroxyl groups. The density functional theory (DFT) calculation method was used to investigate the degradation mechanism and kinetics of DEET in water environment. •OH can attack DEET in two main modes, H-abstraction and •OH-addition, showing different reactivity. H-abstraction reaction is easier to occur compared with •OH-addition reaction. Especially the hydrogen on branch chain of DEET is more readily to be attacked by •OH. In the aqueous phase, the total rate constant is 2.04 × 109 M−1 s−1 at 298 K. Calculated results showed that R5, R6, R8, R9 and R12 paths preferentially occur. Under alkaline conditions, it can significantly inhibit the DEET degradation. The influence of natural organic matter (NOM) in water and oxidant dosage, DEET concentration was also considered. The response surface methodology (RSM) was used to optimize the process parameters. The maximum degradation efficiency of 95.64% can be achieved under optimal conditions. Since most of the products are homologues of the parent compound, their acute and chronic toxicity are not significantly reduced. The products are non-mutagenic and non-bioconcentrated, but they are developmentally toxic. [Display omitted] [ABSTRACT FROM AUTHOR]

The mechanisms of OH-initiated oxidation of allyl acetate in the presence of O2/NO have been investigated by performing density functional theory calculations. Two patterns (OH-addition and H-abstraction) of the initial reaction and the subsequent reactions of the primarily produced intermediates (IM1, IM2, and IM4) have been proposed. The OH-addition reactions are more favorable than the H-abstraction reactions, but H-abstraction from the CH2 group cannot be ignored. The major degradation products have been identified. The rate coefficients and the branching ratios of the primary reactions are obtained over the temperature of 200-500 K and the pressure range of 0.001-1000 atm. The total rate coefficient is 3.17 × 10−11 cm3 molecule−1 s−1 at 298 K and 1 atm. With respect to the typical concentration of OH radical (2.0 × 106 molecule cm−3), the atmospheric lifetime of AAC is estimated to be 4.40 h. [ABSTRACT FROM AUTHOR]

Metal-free photocatalysts for high efficient photocatalytic degradation of pollutants have attracted growing concern in recent years. Herein, relying on density functional theory (DFT) calculations, boron and phosphorus doped C 2 N layers were explored for the potential of utilization as photocatalysts for 4, 5-dichloroguaiacol (4, 5-DCG) removal. Our computations revealed that the adsorption energy of 4, 5-DCG on B@N-doped C 2 N layers were 26.56 kcal mol−1, and the Δ G ≠ of initial reactions of 4, 5-DCG with OH were also reduced onto the B@N-doped C 2 N substrates. The band gap of B@N-doped C 2 N was 2.27 eV. The obtained results showed that the doping of boron atom into C 2 N layer narrows bandgap, and retains well catalytic performance and adsorption properties. Hence, B@N-doped C 2 N layer is a promising photocatalyst for organic pollutants removal. Possible degradation pathways of 4, 5-DCG and aquatic toxicity assessment during degradation were also carried out. Products with higher toxicity would be formed and the transformation products were still toxic to three nutrient levels of aquatic organisms (green algae, fish, and daphnia). • B and P doped monolayer C 2 N were determined by theoretical study. • B@N-doped C2N layer is a promising photocatalyst for organic pollutants removal. • The adsorption capacity of boron-doped C 2 N for pollutants was enhanced. • The transformation products of 4, 5-dichloroguaiacol are still toxic. [ABSTRACT FROM AUTHOR]

Thisstudy investigates the decomposition of 2,2′,4,4′,5-pentabrominateddiphenyl ether (BDE99), a commonly detected pollutant in the environment.Debromination channels yielding tetrabrominated diphenyl ethers andhydrogen abstracting aromatic bromine atom formations play significantroles in the reaction of BDE99 + H, in which the former absolutelypredominates bimolecular reactions. Polybrominated dibenzo-p-dioxins (PBDDs) and polybrominated dibenzofurans (PBDFs)can be produced during BDE99 pyrolysis, especially for PBDFs underinert conditions. The expected dominant pathways in a closed systemare debromination products and PBDF formations. The bimolecular reactionwith hydroxyl radical mainly leads to hydroxylated BDE99s rather thanhydroxylated tetrabrominated diphenyl ethers. PBDDs are then generatedfrom ortho-hydroxylated PBDEs. HO2radicalreactions rarely proceed. The total rate constants for the BDE99 reactionwith hydrogen atoms and hydroxyl radicals exhibit positive dependenceon temperature with values of 1.86 × 10–14and5.24 × 10–14cm3molecule–1s–1at 298.15 K, respectively. [ABSTRACT FROM AUTHOR]

The reaction mechanisms for the atmospheric hydroxylation of n-butyl vinyl ether ( n-BVE), iso-butyl vinyl ether ( i-BVE), and tert-butyl vinyl ether ( t-BVE) were investigated by using quantum chemical method in this paper. The geometry optimizations and frequency calculations were carried out at the MPWB1K/6-31+G(d,p) level, and the accurate energetic parameters were obtained by the MPWB1K/6-311++g(3df,2p) method. The reaction mechanisms for the title reactions have been presented. Ten possible reaction channels were discussed for the primary hydroxylation of n-BVE and t-BVE, while fourteen pathways for i-BVE. Three favorable reaction pathways were chosen for each isomer to undergo further investigation. Major products are n-butyl formate, iso-butyl formate, tert-butyl formate, and HCHO. The rate constants of the primary reactions were calculated over the temperature range of 200-400 K and the pressure range of 100-2,000 Torr by employing MESMER program. At 298 K and 760 Torr, the whole rate constants of n-BVE + OH, i-BVE + OH, and t-BVE + OH are 12.3 × 10, 9.32 × 10 and 5.75 × 10cmmolecules, respectively. Additionally, the lifetimes of the three isomers with respect to OH radical are $$\tau$$ = 1.13 h, $$\tau$$ = 1.49 h, and $$\tau$$ = 2.41 h. [ABSTRACT FROM AUTHOR]

TheCl-initiated oxidation reactions of methyl vinyl ether (MVE) are analyzedby using the high-level composite method CBS-QB3. Detailed chemistryfor the reactions of MVE with chlorine atoms is proposed accordingto the calculated thermodynamic data. The primary eight channels,including two Cl-addition reactions and six H-abstraction reactions,are discussed. In accordance with the further investigation of thetwo dominant additional routes, formyl chloride and formaldehyde arethe major products. Over the temperature range of 200–400 Kand the pressure range of 100–2000 Torr, the rate constantsof primary reactions are calculated by employing the MESMER program.H-abstraction channels are negligible according to the value of rateconstants. During the studied temperature range, the Arrhenius equationis obtained as ktot= 5.64 × 10–11exp(215.1/T). The totalrate coefficient is ktot= 1.25 ×10–10cm3molecule–1s–1at 298 K and 760 Torr. Finally, the atmosphericlifetime of MVE with respect to Cl is estimated to be 2.23 h. [ABSTRACT FROM AUTHOR]

The substitution reactions of HSiLiF ( A) with SiHXH (X = F, Cl, Br, O, N; n = 1, 1, 1, 2, 3) have been studied using DFT and ab initio methods. The results indicate that the substitution reactions of A with SiHXH proceed via two reaction paths, I and II. The following conclusions emerge from this work. (i) The substitutions of A with SiHXH are nucleophilic reactions and occur in a concerted manner. Path I is more favorable than path II. The substitution barriers of A with SiHXH for path I decrease with the increase of the atomic number of X for the same period systems, whereas the barriers increase with the increase of the atomic number of X for the same family systems. (ii) The substitution products are HSiFSiH and LiXH. If the H atoms in SiH of SiHXH are substituted by different atoms or groups, silanes HSiFSiH obtained via paths I and II would be enantiomers. (iii) All the substitution reactions of A with SiHXH are exothermic. [ABSTRACT FROM AUTHOR]