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Typical metal–organic frameworks (MOFs) usually suffer from a limited visible light-trapping ability and easy recombination of charge carriers, hindering their photocatalytic applications. Acetylacetone (AA), leveraging its exceptional coordination capabilities, serves as a versatile and effective modifier for enhancing the photocatalytic activity of MOFs via a post-synthesis approach. The synthesis of diketone-anchored MOFs with AA can be achieved by first diazotizing the amino groups on the ligands of MOFs, followed by a condensation reaction between AA and the resulting azide. Gradient AA loadings ranging from 17% to 98% were obtained, showcasing the tunability of this approach. Interestingly, a sub-stoichiometric effect was exhibited between the AA loading and the visible photocatalytic performance of the modified photocatalyst. The singlet oxygen yields of MIL-125-AA-37% and MIL-125-AA-54% were about 1.3 times that of MIL-125-AA-17% and 3.0 times that of MIL-125-AA-98%. The improved photocatalytic activity could be attributed to the fact that the AA modification altered the electron density of the Ti metal center, leading to the creation of a significant amount of oxygen defects. This alteration resulted in a reduction in the recombination of charge carriers and thus a better charge separation. In short, AA modification provides a new strategy to maximize the visible photocatalytic performance of MOFs. [ABSTRACT FROM AUTHOR]

Acetylacetone (AcAc) has proven to be a potent photo-activator in the degradation of color compounds. The effects of AcAc on the photochemical conversion of five colorless pharmaceuticals were for the first time investigated in both pure and natural waters with the UV/H 2 O 2 process as a reference. In most cases, AcAc played a similar role to H 2 O 2 . For example, AcAc accelerated the photodecomposition of carbamazepine, oxytetracycline, and tetracycline in pure water. Meanwhile, the toxicity of tetracyclines and carbamazepine were reduced to a similar extent to that in the UV/H 2 O 2 process. However, AcAc worked in a way different from that of H 2 O 2 . Based on the degradation kinetics, solvent kinetic isotope effect, and the inhibiting effect of O 2 , the underlying mechanisms for the degradation of pharmaceuticals in the UV/AcAc process were believed mainly to be direct energy transfer from excited AcAc to pharmaceuticals rather than reactive oxygen species-mediated reactions. In natural waters, dissolved organic matter (DOM) played a crucial role in the photoconversion of pharmaceuticals. The role of H 2 O 2 became negligible due to the scavenging effects of DOM and inorganic ions. Interestingly, in natural waters, AcAc first accelerated the photodecomposition of pharmaceuticals and then led to a dramatic reduction with the depletion of dissolved oxygen. Considering the natural occurrence of diketones, the results here point out a possible pathway in the fate and transport of pharmaceuticals in aquatic ecosystems. [ABSTRACT FROM AUTHOR]

• Acetylacetone outperformed H 2 O 2 in degrading algal metabolites under xenon irradiation. • Protein-like constituents were more susceptible to photodegradation by acetylacetone. • The biological toxicity of microcystin-LR was greatly reduced after photooxidation. • The photoactivity of acetylacetone was limited by alkaline pH, not by inorganic ions. Inactivation of cyanobacterial cells and simultaneous control of secondary metabolites is of significant necessity for the treatment of cyanobacteria-laden water. Acetylacetone (AcAc) has been reported a specific algicide to inactivate Microcystis aeruginosa (M. aeruginosa) and an effective light activator to degrade pollutants. This study systematically investigated the photodegradation ability of AcAc under xenon (Xe) irradiation on the secondary metabolites of M. aeruginosa , mainly algal organic matter (AOM), especially toxic microcystin-LR (MC-LR). Results showed that AcAc outperformed H 2 O 2 in destructing the protein-like substances, humic acid-like matters, aromatic proteins and fulvic-like substances of AOM. For MC-LR (250 µg/L), 0.05 mmol/L AcAc attained the same degradation efficiency (87.0%) as 0.1 mmol/L H 2 O 2. The degradation mechanism of Xe/AcAc might involve photo-induced energy/electron transfer and formation of carbon center radicals. Alkaline conditions (pH > 9.0) were detrimental to the photoactivity of AcAc, corresponding to the observed degradation rate constant (k 1 value) of MC-LR drastically decreasing to 0.0013 min−1 as solution pH exceeded 9.0. The PO 4 3− and HCO 3 − ions had obvious inhibition effects, whereas NO 3 − slightly improved k 1 value from 0.0277 min−1 to 0.0321 min−1. The presence of AOM did not significantly inhibit MC-LR degradation in Xe/AcAc system. In addition, the biological toxicity of MC-LR was greatly reduced after photoreaction. These results demonstrated that AcAc was an alternative algicidal agent to effectively inactivate algal cells and simultaneously control the secondary metabolites after cell lysis. Nevertheless, the concentration and irradiation conditions should be further optimized in practical application. [Display omitted] [ABSTRACT FROM AUTHOR]

The acetylacetone (AA) mediated photochemical process has been proven as an efficient approach for decoloration. For azo dyes, the UV/AA process was several to more than ten times more efficient than the UV/H 2 O 2 process. Iron is one of the most common elements on the earth. It is well known that iron can improve the UV/H 2 O 2 process through thermal Fenton and photo-Fenton reactions. What will be the role of iron in the UV/AA process? Could iron–AA complexes act as photocatalysts in environmental remediation? To answer these questions, the photo-degradation of an azo dye, Acid Orange 7 (AO7), was conducted under the variant combinations of AA with iron species in both ionic (Fe 2+ , Fe 3+ ) and complex (Fe(AA) 3 ) forms. The pseudo-first-order decoloration rate constants of AO7 in these photochemical processes followed such an order: UV/Fe(II)/AA < UV/Fe(III)/AA < UV/Fe(AA) 3 < UV/AA. The results demonstrate that iron species, in either ionic or complex form, acts as an inhibitor rather than a catalyst in the UV/AA process. Based on spectroscopic analysis, the inner filter effect of iron and the competition between Fe(III) and AA for the complexation with AO7 were attributed to the inhibition effect of iron on the UV/AA process. The understanding of the role of iron provides insight into the practical application of the UV/AA process. [ABSTRACT FROM AUTHOR]

Low-cost and environmentally friendly mediators could facilitate the application of laccase (EC 1.10.3.2) in variant biotechnological processes. Acetylacetone (AA) represents an inexpensive and low toxic small molecular diketone that has been proven as an effective mediator for laccase in free radical polymerization. However, the potential of AA as a mediator for laccase in pollutant detoxification and/or degradation is still unknown. In this work, the roles of AA in laccase-induced polymerization and transformation were investigated. AA was demonstrated to be a highly efficient mediator in the laccase-induced grafting copolymerization of acrylamide and chitosan. The efficacy of AA in the laccase-induced decoloration of malachite green (MG) was compared with that of the widely used 1-hydroxybenzotriazole (HBT). The laccase-AA system had the highest turnover number (TON, 39.1 μmol/U), followed by the laccase-only system (28.5 μmol/U), while the TON of the laccase-HBT system was the lowest (14.9 μmol/U). The pseudo-first-order transformation rate constant ( k) of MG in the laccase-AA system was up to 0.283 h under the given conditions, while the k of AA caused by laccase was only 0.008 h. In the five-cycle run, the concentration of AA remained stable. The larger TON of the laccase-AA system and the stability of AA in the cycling runs demonstrate that AA was more recyclable than HBT in the LMS, leading to a prolonged serving life of laccase. These results suggest that AA might be a potential redox mediator for laccase. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Acetylacetone (AA) played double roles in the enzymatic transformation of MG. • NTB was identified as a key intermediate in laccase-catalyzed transformation of MG. • AA inhibited the transformation of MG by quenching the reactive NTB+. • AA reduced the consumption of laccase by quenching the reactive NTB+. • The inhibition effect of AA was both time and concentration dependent. Abstract The potential of acetylacetone (AA) as a mediator of laccase has been tested in the enzymatic transformation of malachite green (MG). AA inhibited the laccase-induced transformation of MG at the beginning of incubation but extended the working life of laccase in long runs. To elucidate the underlying mechanisms, the transformation of MG in the laccase-AA system was systematically investigated. The inhibition of AA on the enzymatic transformation of MG conformed to the partial mixed model. The transformation of N,N,N',N'-tetramethyl-1,1′-biphenyl-4,4′-diamine (NTB) was identified as the rate-controlling step in the laccase system. The generated NTB was oxidized to NTB+ by laccase, which acted as a redox mediator to accelerate the transformation of MG. The addition of AA to the enzymatic system quenched the NTB+ by forming an intermediate complex of AA-NTB. This quenching reaction led to two contrary effects: the acceleration caused by NTB+ in the enzymatic transformation of MG was inhibited whereas the formation of AA-NTB complex enhanced the further transformation at the later stage. As a result, less laccase was consumed, which explained the extended working life of laccase in the long runs. The understanding of these mechanisms are helpful for the better use of laccase as a green biocatalyst. [ABSTRACT FROM AUTHOR]

The redox conversion of arsenite and nitrate has direct effects on their potential environment risks. Due to the similar reduction potentials, there are few technologies that can simultaneously oxidize arsenite and reduce nitrate in one process. Here, we demonstrate that a diketone-mediated photochemical process could efficiently do this. A combined experimental and theoretical investigation was conducted to elucidate the mechanisms behind the redox conversion in the UV/acetylacetone (AA) process. Our key finding is that UV irradiation significantly changed the redox potential of AA. The excited AA, 3 (AA)*, acted as a semiquinone radical-like electron shuttle. For arsenite oxidation, the efficiency of 3 (AA)* was 1–2 orders of magnitude higher than those of quinone-type electron shuttles, whereas the consumption of AA was 2–4 orders of magnitude less than those of benzonquinones. The oxidation of arsenite and reduction of nitrate could be both accelerated when they existed together in UV/AA process. The results indicate that small diketones are some neglected but potent electron shuttles of great application potential in regulating aquatic redox reactions with the combination of UV irradiation. [ABSTRACT FROM AUTHOR]

Acetylacetone (AA), due to the peculiar enol-keto structures, has attracted wide scientific interests. In terms of photo-decolorization, it works much more efficiently than the well-known H 2 O 2 . However, there is very limited information on the photochemistry of AA in aqueous solutions. Herein, the photolysis kinetics, quantum yield, mass balance, decomposition pathway, and bioavailability of AA during UV irradiation were systematically investigated. It seems that photophysical processes predominated over photochemical ones when AA was irradiated with UV light. Although the quantum yield of AA (0.116) was much lower than that of H 2 O 2 (1.0), the stronger light absorption of AA and the better overlap of the AA absorption spectrum with the solar emission spectrum, as well as the direct energy/electron transfer mechanisms, ensured its high efficiency in photochemical processes. The main degradation products of AA in photochemical processes were similar to the metabolic products in bio-fermentation. Besides, the irradiated AA solution showed a high bioavailability to the cells in activated sludge. Therefore, the UV/AA process might be a promising pre-treatment approach for bio-treatment. The results provide new insights into the photochemical fate and implication of β -diketones in aqueous solutions. [ABSTRACT FROM AUTHOR]

Organic ligands play pivotal roles in the synthesis and modification of photocatalysts. Small molecular diketones, exemplified by acetylacetone (acac), are a promising class of ligands. Nevertheless, a comprehensive review of their roles in photocatalysis has not yet been conducted. This gap hinders the rational design and application of photocatalysts by using diketones as functional ligands. It is therefore imperative to provide a comprehensive examination of this topic. This review critically summarizes the utilization of acac in photocatalysis from four aspects: the chemical nature and reactivity of acac, the roles of acac in the synthesis and modification of photocatalysts (especially the well-known TiO 2), its influence on the photocatalytic processes, and the existing challenges and future prospects for acac-mediated photocatalysis. By providing a critical analysis of the established applications of acac in photocatalysis, we aim to inspire further advancements in the field rooted in fundamental theoretical principles. [Display omitted] • β-Diketones and diketonates play crucial roles in the fabrication of photocatalysts. • The roles of β-diketones in photocatalysis are critically reviewed for the first time. • The photocatalytic mechanism manipulation via β-diketones is summarized. • Future perspectives on coordination-tuned photocatalysis are proposed. [ABSTRACT FROM AUTHOR]

Ligands may increase the yields of reactive oxygen species (ROS) in zero-valent iron (ZVI)/O 2 systems. To clarify the relationship between the properties of ligands and their effects on the oxidative removal of contaminants, five common ligands (formate, acetate, oxalate, ethylenediaminetetraacetic acid (EDTA), and phosphate) as well as acetylacetone (AA) were investigated with arsenite (As(III)) as the target contaminant at three initial pH values (3.0, 5.0, and 7.0). The addition of these ligands to the ZVI/O 2 system resulted in quite different effects on As(III) removal. EDTA enhanced the oxidation of As(III) to arsenate (As(V)) but inhibited the removal of As(V). Oxalate was the only ligand in this work that accelerated both the removal of As(III) and As(V). By analyzing the ligand effects from the four aspects: dissolution of surface iron (hydr)oxides, corrosion of ZVI, reaction with ROS, and interference with precipitation, the following properties of ligands were believed to be important: ability to provide dissociable protons, complexation ability with iron, and reactivity with ROS. The complexation ability is a double-edged sword. It could enhance the generation of ROS by reducing the reduction potential of the Fe(III)/Fe(II) redox couple, but also could inhibit the removal of arsenic by coprecipitation. The elucidated relationship between the key property parameters of ligands and their effects on the ZVI/O 2 system is helpful for the rational design of effective ZVI/ligand/O 2 systems. Unlabelled Image [ABSTRACT FROM AUTHOR]

Abstract Quinones are components of electron transport chains in photosynthesis and respiration. Acetylacetone (AA), structurally similar to benzoquinone (BQ) for the presence of two identical carbonyl groups, has been reported as a quinone-like electron shuttle. Both BQ and AA are important chemicals in the aquatic environment. However, little information is known about their interactions if co-existed. We found here that AA significantly enhanced the conversion of BQ. By analyzing the evolution of chemical concentration, solution pH, dissolved oxygen, and the final products, the interactions between AA and BQ were elucidated. The reactions between BQ and AA generated oxygen but ultimately led to the reduction of solution pH and dissolved oxygen. The reactions proceeded faster under indoor lighting condition than in the dark. The formation of semiquinone radicals is believed as the primary step. The secondary AA-derived radicals might be strongly oxidative or reductive, depending on the concentration of dissolved oxygen. Insoluble humus was generated in the mixture of BQ and AA. These results suggest that the presence of AA might interfere with photosynthesis and respiration through the interactions with quinones. Graphical abstract Image 1 Highlights • Reactions between BQ and AA were investigated in dark and lighting conditions. • The reactions proceeded faster under indoor lighting condition than in the dark. • AA significantly enhanced the conversion of BQ by acting as an electron donor. • The formation of semiquinone radicals was the primary step. • Reactive AA-derived radicals were generated in the mixture of BQ and AA. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Acetylacetone (AA) can enhance the UV decomplexation of Cu(II)-EDTA. • Direct photo-decarboxylation via LMCT was the first step in the decomplexation. • Cu-mediated photo-Fenton reactions played a dominant role in the decomplexation. • AA facilitated the photo-Fenton reactions by reducing Cu2+ to Cu+. • H 2 O 2 generated in the redox cycle of AA also contributes to the Fenton-like reactions. Abstract Cu(II)-EDTA is a stable metal-organic complex in electroplating wastewater and is hard to be removed by the conventional precipitation method. UV decomplexation is a useful strategy for its removal. Here, we report that acetylacetone (AA) can enhance the decomplexation of Cu(II)-EDTA by facilitating the photo-Fenton reactions. Under UV irradiation, the pseudo-first-order decomplexation rate constant (k1) of Cu(II)-EDTA (0.3 mM) was enhanced 2–3 times by AA at a [AA]:[Cu(II)-EDTA] molar ratio of 1, whereas the photochemical consumption of AA was reduced 2–3 times by the presence of Cu(II)-EDTA. Based on intermediate species and product analyses, the first step in decomplexation was confirmed as direct photo-decarboxylation of Cu(II)-EDTA via the ligand to metal charge transfer (LMCT) process. Once Cu+ was formed, there would be Fenton-like reactions. AA facilitated the photo-Fenton reactions in two ways: (1) reducing Cu2+ to Cu+ and (2) providing more H 2 O 2 via the redox cycle of AA. Besides, the degradation products of AA could also involve in the decomplexation of Cu(II)-EDTA through LMCT. The work here might provide a promising solution for the decomplexation of metal-organic complexes in industrial wastewater. [ABSTRACT FROM AUTHOR]

Titanium xerogel coagulant (TXC) worked better than titanium tetrachloride (TC) and polytitanium chloride (PTC) in a wider pH/dose range for the removal of turbidity. However, the underlying mechanisms were not comprehensively understood. In this work, the better coagulation performance of TXC than TC and PTC was systematically elucidated from the following aspects: the physicochemical properties of the three coagulants, the removal of turbidity and organic matter, and the complexation reactions in coagulation. The results demonstrate that the merits of TXC were attributable to the following characteristics: (1) the higher surface charge density/total surface site concentration/isoelectric point of TXC hydrolysates, (2) the formation of TXC hydrolysates with a net-work structure, and (3) the strong binding affinity of TXC hydrolysates to organic matter caused by the bonded acetylacetone in the TXC framework. In short, the hydrolysis behavior of TXC significantly differed from both its precursor, TC, and the prehydrolyzed PTC. The difference in the hydrolysis of TXC was derived from the gelation process, which led to the polymerization of Ti in a way different from prehydrolyzation. The elucidation of the hydrolysis mechanisms is useful for the better application of Ti-based coagulants and may shed light on the preparation of other metal salts. [ABSTRACT FROM AUTHOR]

Biodegradability and toxicity are two important indexes in considering the feasibility of a chemical process for environmental remediation. The acetylacetone (AA) mediated photochemical process has been proven as an efficient approach for dye decolorization. Both AA and its photochemical degradation products had a high bioavailability. However, the biocompatibility and ecotoxicology of the UV/AA treated solutions are unclear yet. In the present work, we evaluated the biocompatibility and toxicity of the UV/AA treated solutions at both biochemical and organismal levels. The biodegradability of the treated solution was evaluated with the ratio of 5-d biological oxygen demand (BOD 5 ) to chemical oxygen demand (COD) and a 28-d activated sludge assay (Zahn-Wellens tests). The UV/AA process significantly improved the biodegradability of the tested dye solutions. Toxicity was assessed with responses of microorganisms (microbes in activated sludge and Daphnia magna ) and plants (bok choy, rice seed, and Arabidopsis thaliana ) to the treated solutions, which showed that the toxicity of the UV/AA treated solutions was lower or comparable to that of the UV/H 2 O 2 counterparts. The results are helpful for us to determine whether the UV/AA process is applicable to certain wastewaters and how the UV/AA process could be effectively combined into a sequential chemical-biological water treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • The β -diketone structure of AA was of vital importance for high-rate photobleaching. • Substituents significantly affected the photochemical activity of AAs. • Electron-donating groups at central carbon enhanced the production of organic radicals. • Electron-withdrawing groups reduced the photobleaching performance of AAs. • Both direct electron transfer and organic radicals-attack were involved in UV/AAs. Acetylacetone (AA), which has two tautomers (diketo and enol), has been found to be a potent photo-activator for wastewater treatment. However, the crucial structural characteristics in the photo-activity remained unclear. Herein, the performance of 16 AA derivatives and structural analogues (AAs) was extensively evaluated for a real dyeing wastewater and a model dye solution under UV irradiation. The results indicate that the straight-chain aliphatic 1,3-diketone structure was crucial in the high-rate photobleaching. Photo-induced direct electron transfer by enolic AAs and indirect electron transfer with free radicals generated from the cleavage of ketone AAs were the two main mechanisms. The substituents affect the keto-enol tautomerization and the charge population, thereby influencing the photochemical activity of AAs. Electron-donating groups (e.g., -CH 3 , -(CH 3) 2 , -CH 2 CH 3) at the central carbon in AAs would increase the content of the diketone form and promote the generation of organic radicals from α -cleavage. By contrast, the presence of electron-withdrawing groups (such as -Cl, -(F) 3 , and -C 2 H 4 Br) might lead to the hydrolysis or hydration of AAs, and consequently depressed the photobleaching rate. The results here are valuable for the design of more efficient and eco-friendlier photo-activators for environmental remediation based on diketone photochemistry. [ABSTRACT FROM AUTHOR]

Light source is a crucial factor in the application of a photochemical process, which determines the energy efficiency. The performances of acetylacetone (AA) in conversion of aqueous contaminants under irradiation with a low-pressure mercury lamp, a medium-pressure mercury lamp, a xenon lamp, and natural sunlight were investigated and compared with those of H 2 O 2 as reference. In all cases, AA was superior to H 2 O 2 in the degradation of Acid Orange 7. Using combinations of the different light sources with various cut-off and band-pass filters, the spectra responses of the absorbed photons in the UV/AA and UV/H 2 O 2 processes were determined for two colored and two colorless compounds. The photonic efficiency ( φ ) of the two photochemical processes was found to be target-dependent. A calculation approach for the inner filter effect was developed by taking the obtained φ into account, which provides a more accurate indication of the reaction mechanisms. [ABSTRACT FROM AUTHOR]

Surface passivation is a key limiting factor in the application of zero-valent iron (ZVI) for water remediation. Addition of ligands is a useful approach to overcome this issue. In this work, a small amount of acetylacetone (AA) (0.5 mM) was found highly efficient to enhance the reduction of nitrate by ZVI at near neutral conditions (pH 6.0) with the formation of considerable black coating on ZVI. At an initial nitrate concentration of 20 mg N/L, the pseudo first-order reduction rate constant of nitrate in the ZVI-AA-NO 3 − system was 0.0991 h −1 , which was 52 times higher than that in the ZVI-NO 3 − system. Under otherwise identical conditions, the other five ligands, including EDTA, formate, acetate, oxalate, and phosphate, had negligible effects. Based on the p K a values of these ligands and the final species of iron, the ligand effects on nitrate reduction by ZVI were summarized from three aspects: (1) the ability to offer potentially dissociable protons from the ligands; (2) the complexation ability to eliminate iron (hydr)oxide precipitates from the surface of ZVI; and (3) the ability to lower down the redox potentials of iron species. The good performance of AA in these three aspects makes it advantage over the other ligands. A cycle test up to six runs demonstrates that AA could continuously take effect in the ZVI system. The results here point out the potential of AA as an effective ligand in ZVI system for enhanced contaminant transformation. [ABSTRACT FROM AUTHOR]

[Display omitted] • AA promoted the degradation of AO7 under UV irradiation. • Under solar irradiation, AA inhibited the self-sensitized degradation of AO7. • AA-CH 2 -AA had a nonstoichiometric enhancement effect on the photodegradation of AO7. • AA-CH 2 -AA interacted with the generated 1O 2 from the self-sensitization of AO7. • Electron-donating α -substituents make the AA derivatives less sensitive to energy transfer. Self-sensitized degradation is a typical fate of azo dyes in aquatic systems but its kinetics is far too slow to meet the requirement for a thorough decolorization. Small diketones were found being able to enhance the degradation of dyes under UV irradiation and the introduction of an electron-denoting group at the α -position of the simplest β -diketone (acetylacetone, AA) had a further enhancement effect on the degradation. However, it is unclear whether such enhancement effects exist in the solar-irradiated systems. To clarify this question, the effects of three AA derivatives were investigated with Acid Orange 7 (AO7) as a representative azo dye. Compared with the AA derivatives with a methyl or an ethyl group at the central carbon (AA-CH 3 and AA-CH 2 CH 3), 3,5-diacetylheptane-2,6-dione (AA-CH 2 -AA, which is a condensed combination of AA and AA-CH 3) showed a >2-fold stronger enhancement effect. The nonstoichiometric enhancement effect of AA-CH 2 -AA on AO7 photodegradation disclosed a novel pathway for dye degradation: AA-CH 2 -AA could enhance the degradation of AO7 by reacting with the photo-sensitized 1O 2 , whereas AA led to an inhibitory effect on the self-sensitized degradation of AO7 by quenching the excited state of the azo dye. These results demonstrate that small diketones could be designed to regulate the photodegradation of azo dyes in multiple pathways. [ABSTRACT FROM AUTHOR]

Laccase is a green biocatalyst. It works with molecular oxygen and produces water as the only by-product. However, its practical application is far less than satisfactory due to the low stability/poor reusability of free laccase and the potential secondary pollution caused by dissolved mediators. To address those bottlenecks in laccase-based catalysis, a novel biocatalyst (Immo-LMS) was fabricated by simultaneously immobilizing both laccase and a mediator (acetylacetone, abbreviated as AA) into a hydrogel through the laccase-AA initiated polymerization. This self-initiated immobilization process avoided the forced conformational change of laccase in the passive embedding to pre-existing carriers. Resulting from the effective cooperation of laccase and AA, the Immo-LMS had the highest substrate conversion quantity to malachite green, followed by the sole immobilized laccase and the immobilized laccase with an external mediator. Besides the improved activity, the Immo-LMS showed enhanced stability. The good performance of the Immo-LMS suggests that the co-immobilization of laccase and mediator through the self-initiated one-pot process was a promising strategy for the immobilization of laccase, which is expected to be helpful to cut down the running cost as well as the potential toxicity that come from mediators in the practical application of laccase. [ABSTRACT FROM AUTHOR]

[Display omitted] • UV/diketones were more efficient than UV/sulfite and UV/TiO 2 for Se(IV) reduction. • UV/diketones had a wide working pH range without deoxygenation. • Acetylacetone worked in a way different from that of diacetyl. • Carbon-centered free radicals played a role in Se(IV) reduction by UV/diacetyl. • Photo-induced complexation was involved in UV/acetylacetone. The reduction of highly toxic selenite (Se(IV)) to insoluble elemental selenium (Se(0)) is an effective strategy to alleviate the toxicity and to recover valuable Se from contaminated waters. Acetylacetone (AcAc) and diacetyl (BD) were found to be able to photoreduce Se(IV) into selenium nanoparticles. However, the kinetics and molecular mechanisms of the diketone-mediated Se(IV) reduction are still open to discussion. Herein, the photo-reduction of Se(IV) was studied with the two diketones and sulfite as reductants, as well as TiO 2 as a photocatalyst. The results demonstrate that the two diketones were more effective and robust than sulfite. The reduction rate constants of Se(IV) in the UV/diketone systems were 5.1–6.5 times higher than those of UV/sulfite in a wide pH range (1.0–8.0) and without the need for deoxygenation. Compared with UV/TiO 2 reduction, no complicated separation processes were needed after reduction with UV/diketones. After 1 h of irradiation, the recovery rates of Se(0) were 82% and 75% in UV/AcAc and UV/BD, respectively. Interestingly, the reactions that occurred in the UV/AcAc and UV/BD systems were unexpectedly different. On the base of reactive species scavenging experiments and quantum chemical calculations, acetyl radical (CH 3 C•(O)) and its hydrated product (CH 3 C•(OH) 2) were found to play dominant roles in the UV/BD system, whereas the role of photo-induced complexation between hydrated AcAc and Se(IV) might not be neglected in the UV/AcAc system. Such a difference provides us with some room for choice and adjustment in the further application of UV/diketones for the treatment of Se(IV)-laden wastewater or for the reduction of some other similar metalloids. [ABSTRACT FROM AUTHOR]

• Diketones could enhance the photoconversion of carbamazepine as well as H 2 O 2. • The promotion effect of diketones was pH-dependent and favorable in acidic solution. • Attack of organic peroxyl radicals was the main mechanism in UV/diketone systems. • Mutagenic acridine was the main cumulative intermediate in the presence of diketones. In surface waters, photogenerated transients (e.g., hydroxyl radicals, carbonate radicals, singlet oxygen and the triplet states of dissolved organic matter) are known to play a role in the transformation of biorecalcitrant carbamazepine (CBZ). Small diketones, such as acetylacetone (AcAc) and butanedione (BD), are naturally abundant and have been proven to be effective precursors of carbon and oxygen centered radicals. However, the photochemical kinetics and mechanisms of coexisting diketones and CBZ are barely known. Herein, the effects of AcAc and BD on the photochemical conversion of CBZ were investigated compared with H 2 O 2 which was the main ·OH precursor in the environment. An enhancing effect was observed for the degradation of CBZ by the addition of diketones. The enhancing effect of diketones was pH-dependent and much more significant than H 2 O 2 under simulated solar irradiation. On the basis of the identification of transient species and the competition kinetic model, organic peroxyl radicals were found to play a dominant role in CBZ photodegradation, and the second-order rate constants of the reaction between CBZ and peroxyl radicals were determined to be approximately 107–108 M–1s–1. Furthermore, mutagenic acridine was found to be the major cumulative intermediate with a yield of > 30% in the presence of diketones, which might be an environmental concern. This work indicates that the coexistence of diketones and persistent organic pollutants might lead to some detrimental effects on aquatic environments if the water is exposed to sunlight. [Display omitted]. [ABSTRACT FROM AUTHOR]

Highlights: [•] AcAc was used as a photo-activator for the photodecoloration of AO7. [•] The UV/AcAc process was more effective for AO7 decoloration than the UV/H2O2 method. [•] The UV/AcAc process significantly improved the biodegradability of the AO7 solution. [•] A self-acceleration phenomenon was observed for the UV/AcAc process. [•] The possible pathways of AO7 degradation in the UV/AcAc process were proposed. [Copyright &y& Elsevier]

Post-synthetic modification with β -diketone has been proven as an effective strategy to improve the visible light response activities of metal-organic frameworks (MOFs). Nevertheless, the effects of the anchored-diketones on the excitonic behaviors and photocatalytic mechanisms of MOFs are still unclear. Herein, two MOFs (MIL-101 with CrIII and MIL-101 with AlIII) were employed as prototypical materials to further understand this post-synthetic modification strategy. Diketone anchoring could enhance the photocatalytic generation of singlet oxygen (1O 2) by the two MOFs in a joint mechanism: exciton-mediated energy transfer and photosensitization. Diketone anchoring induced triplet exciton was found playing an important role in the photocatalytic generation of 1O 2. The photosensitization of the anchored-diketone also played a key role in the photocatalytic generation of 1O 2. The results here provide a useful guidance for the development of MOFs-based photocatalysts and are helpful to realize the regulation of excitonic behaviors and photocatalytic mechanisms of MOFs. [Display omitted] • Diketone anchoring enhances the photocatalytic performance of MOFs. • The enhanced photocatalysis is mainly attributed to increased 1O 2 production. • Diketone-anchored MIL-101s generate 1O 2 via a joint energy transfer mechanism. • Excitons and triplet anchored-diketone are responsible for 1O 2 production. [ABSTRACT FROM AUTHOR]

[Display omitted] • Post-synthetic modification with β -diketone is a useful strategy to fabricate MOFs. • Diketone anchoring improves the ability of MIL-125 to generate 1O 2. • Diketone-anchored MIL-125 generate 1O 2 via an energy transfer pathway. • Diketone-derived oxygen vacancies account for the enhanced energy transfer. The importance of singlet oxygen (1O 2) in synthesis of fine chemicals, inactivation of viruses and bacteria, degradation of pollutants, and photodynamic therapy has promoted the research on photocatalytic generation of 1O 2. Metal-organic frameworks (MOFs), owing to the tunable structure, are good candidate photocatalysts for 1O 2 generation. However, due to the poor visible-light absorption capacity and the invalid recombination of charge carriers, the 1O 2 generation yields of most MOFs are still limited. Here, we demonstrate that β -diketone anchoring could improve the photocatalytic generation of 1O 2 by MIL-125 through enhanced energy transfer. The enhanced energy transfer was attributed to both the narrowed bandgap and the diketone-derived oxygen vacancies, which function as the trapping sites for charge carriers. The results here shed light on the generation of 1O 2 by visible-light-responsive MOFs and provide a new strategy for the design of MOFs-based photocatalysts. [ABSTRACT FROM AUTHOR]

• UV/acetylacetone was target-selective in the photodegradation of aromatic pollutants. • UV/acetylacetone was more efficient than UV/H 2 O 2 for the degradation of dyes. • OH-substitution was favorable for the dyes to be degraded by UV/acetylacetone. • The protonated enol form of acetylacetone was the key species in photodegradation. • Photo-induced electron transfer between acetylacetone and dye played a key role. Acetylacetone (AA) has proven to be a potent photo-activator for the decolorization of dyes. However, there is very limited information on the quantitative structure–activity relationship (QSAR) and the mechanisms of dye degradation by UV/AA. Herein, the photolysis of 65 aromatic compounds (dyes and dye precursors) was investigated at three pH values (4.0, 6.0, 9.0) by UV/AA and UV/H 2 O 2. The obtained pseudo-first-order photodegradation rate constants (k 1) were processed using statistical analysis. The correlation between the k 1 values and the number of photons absorbed by AA, together with the observed pH effect, suggested that the protonated enol structure of AA plays a crucial role in the photodecolorization of dyes. According to quantum chemical computation, photo-induced direct electron transfer between the excited state of AA and the dye was the main mechanism in the UV/AA process. QSAR models demonstrated that the molecular size and stability were the key factors that determined the efficiency of UV/H 2 O 2 for dye degradation. Statistically, the UV/AA process was target-selective and suffered less from the inner filter effect, which made it more effective than the UV/H 2 O 2 process for dye degradation. The selectivity of the UV/AA process was mainly embodied in the substituent effects: dyes with hydroxyl groups in conjugated systems decomposed faster than those with nitro-substitution or ortho -substituted sulfonate groups. The results can be used for the selection of appropriate photochemical approaches for the treatment of dye-contaminated water. [Display omitted] [ABSTRACT FROM AUTHOR]

• UV irradiation was favorable to the enolization and hydration of acetylacetone (AA). • The hydration of AA made it an active ligand to chromate, Cr(VI). • Complexation played a vital role in UV/AA mediated Cr(VI) reduction. • The results are helpful for the better understanding and design of Cr(VI) reduction. Organic ligands can alter the redox behavior of metal species through the generation of metal-ligand complexes. Photo-induced complexation between ligands and metals is an important, but under-appreciated, aspect of process. Acetylacetone (AA) is a good chelating agent due to keto-enol tautomerization. In the presence of AA, photoreduction of Cr(VI) is accelerated; however, it is unclear exactly how complexation is involved in UV/AA mediated Cr(VI) reduction. On the basis of spectral and kinetic analyses, this study shows that the formation of {Cr(VI)-AA}* complexes is the main mechanism of Cr(VI) reduction by UV/AA. Evidence for this includes (1) the formation rate constant of Cr(III)-AA complexes in the UV system was 2–3 orders of magnitude greater than that in the thermal system; (2) there was a linear relationship between the photons absorbed by AA and the reduction rate constants of Cr(VI); and (3) the reaction appeared initially zero-order in Cr(VI) and turned to first-order as the pool of available Cr(VI) ran out. The results presented here are not only important for the better understanding of the complexation effects in the reduction of Cr(VI), but also crucial for the possible application of the UV/AA process in many other scenarios. [ABSTRACT FROM AUTHOR]

• A facile strategy was developed to modify MOFs for enhanced generation of 1O 2. • A diketone structure was introduced into MOFs via a diazo coupling reaction. • This strategy was widely applicable to MOFs with variant metal nodes. • The absorption edge of the modified MOFs was shifted to longer wavelength side. • More 1O 2 was generated via charge transfer rather than energy transfer. Generation of singlet oxygen (1O 2) with metal-organic frameworks (MOFs) is limited by either poor light harvesting ability of type I MOFs or low availability of type II MOFs. Herein, we report a facile and widely applicable strategy, post-synthetic modification of type I MOFs with photo-redox active acetylacetone (AA) via a diazo coupling reaction, to enhance the visible-light-driven generation of 1O 2 by MOFs. The introduction of AA to MOFs with variant metal nodes, such as Zr, Ti, Al, and Cr clusters, leads to intraligand charge transfer (ILCT), which not only strengthens the ligand to metal cluster charge transfer (LCCT) but also expands the photo-responsive edge of MOFs. Via the coupled ILCT and LCCT processes, UiO-66-AA functions as a hybrid type I-type II MOFs, which can efficiently generate 1O 2 even at indoor lighting conditions. This work would open an avenue for the synthesis of MOFs towards diverse visible-light photocatalysis. [ABSTRACT FROM AUTHOR]

• Cu(II)-EDTA is stable in a wide pH range and is hard to be removed. • Fe(III)/UV/NaOH is an effective approach for the removal of Cu(II)-EDTA. • Addition of AA to Fe(III)/UV/NaOH reduced the treatment cost to 46–68%. • Addition of AA to Fe(III)/UV/NaOH reduced the sludge yield to 30%. • Fe(III)+AA/UV/NaOH is a promising method for the treatment of Cu(II)-EDTA. Cu(II)-EDTA is highly stable in a wide pH range (3.0∼12.0) and hard to be removed by the conventional precipitation method. Fe(III) displacement/UV photolysis/alkaline precipitation [Fe(III)/UV/NaOH] has been proposed as a promising method for the removal of Cu(II)-EDTA. Nevertheless, a high dose of Fe(III) is needed in this combined process, resulting in the production of a large amount of hazardous sludge. The photochemistry of Fe(III) is known to be ligand-dependent. Fe(III)-oxalate complexes are strongly photoactive. However, the addition of oxalic acid to the Fe(III)/UV/NaOH process was of little help. Acetylacetone (AA) is a good chelating ligand for many metals and has been proved as an efficient photo-activator. By introducing a low dose of AA ([AA]/[Cu] = 1.5) into the Fe(III)/UV/NaOH process, the Fe(III) dosage ([Fe]/[Cu]) was reduced from 10.4 to 3.2. As a result, the chemical cost was reduced from 13.9 to 7.6 kW h/m3. Meanwhile, the energy cost in the UV photolysis was reduced from 1066.5 to 752.4 kW h/m3. Most importantly, the sludge yields were reduced from 8.3 to 2.7 kg/m3 in a simulated wastewater and from 101.8 to 30.8 kg/m3 in a real electroplating wastewater. Such a sludge reduction is of great significance in mitigating the load of landfill. [ABSTRACT FROM AUTHOR]