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Micro-/mesoporous composite materials with coke-resistant ZSM-5 and three-dimensional large-pore KIT-6 as their micro- and mesoporous components, respectively, were synthesized using a simple in situ overgrowth approach. The hydrothermal stabilities and acidities of the biporous catalysts were found to be significantly enhanced. All composite materials acted as powerful catalysts for toluene oxidation. Among them, Pd/ZK-6% showed the highest catalytic activity, with 90% toluene decomposition at 203 °C, which is more than 30 °C lower than required for Pd/KIT-6. It can be anticipated that the specific surface area and acidity have a synergistic effect on the Pd dispersion. Overall, the catalytic activities were found to be primarily correlated with the specific surface area, support acidity, Pd dispersion, and toluene adsorption capability. [ABSTRACT FROM AUTHOR]

The feasibility and mechanism of five molecular sieves-supported palladium catalysts in elimination of benzene, toluene, and ethyl acetate were investigated. The experimental results indicate that Pd particles are well dispersed on these porous supports with size of 2−10 nm, while mesoporous supports with a larger specific surface area and pore diameter lead to a better dispersion. The activity of freshly made catalysts obeys the following order: Pd/Beta > Pd/ZSM-5 > Pd/SBA-15 > Pd/MCM-48 > Pd/MCM-41. Although Pd/Beta has the highest activity for removal of these VOCs in the beginning, its activity quickly decreases. However, Pd/ZSM-5 and Pd/SBA-15 show a good stability, without activity loss in a 72 h test. Our research reveals that higher acidity can facilitate catalytic reaction and gives rise to higher activity, but it also enhances coke formation and decreases the catalyst stability. In addition, the porosity of supports has a certain impact on catalytic oxidation of VOCs. [ABSTRACT FROM AUTHOR]

Oxygenated volatile organic compounds (OVOCs), emitted in large quantities by the chemical industry, are a major contributor to the formation of ozone and subsequent particulate matter. For the efficient catalytic oxidation of OVOCs, the challenges of molecular activation and intermediate inhibition remain. The construction of bifunctional active sites with specific structures offers a promising way to overcome these problems. Here, the Pd@Layered-CoO x /MFI bifunctional catalyst with core-shell active sites was rationally fabricated though a two-step ligand pyrolysis method, which exhibits a superb oxidation efficiency toward ethyl acetate (EA). Over this, 13.4% of EA (1000 ppm) can be oxidized at just 140 °C with a reaction rate of 13.85 mmol·g Pd -1 ·s -1 , around 176.7 times higher than that of the conventional Pd-CoO x /MFI catalyst. The electronic coupling of the Pd-Co pair promotes the electron back-donation from Pd nanoparticles to the layered CoO x shell and facilitates the formation of Pd 2+ species, which greatly enhances the adsorption and activation of the electron-rich C═O bond of the EA molecules. In addition, the synergy of these core-shell Pd@Layered-CoO x sites accelerates the activation and transformation of *O species, which inhibit the formation of acetaldehyde and ethanol byproducts, ensuring the rapid total oxidation of EA molecules via the Mars-van Krevelen mechanism. This work established a solid foundation for exploring robust bifunctional catalysts for deep OVOC purification.

The widespread presence of formaldehyde (HCHO) pollutant has aroused significant environmental and health concerns. The catalytic oxidation of HCHO into CO 2 and H 2 O at ambient temperature is regarded as one of the most efficacious and environmentally friendly approaches; to achieve this, however, accelerating the intermediate formate species formation and decomposition remains an ongoing obstacle. Herein, a unique tandem catalytic system with outstanding performance in low-temperature HCHO oxidation is proposed on well-structured Pd/Mn 3 O 4 -MnO catalysts possessing bifunctional catalytic centers. Notably, the optimized tandem catalyst achieves complete oxidation of 100 ppm of HCHO at just 18 °C, much better than the Pd/Mn 3 O 4 (30%) and Pd/MnO (27%) counterparts as well as other physical tandem catalysts. The operando analyses and physical tandem investigations reveal that HCHO is primarily activated to gaseous HCOOH on the surface of Pd/Mn 3 O 4 and subsequently converted to H 2 CO 3 on the Pd/MnO component for deep decomposition. Theoretical studies disclose that Pd/Mn 3 O 4 exhibits a favorable reaction energy barrier for the HCHO → HCOOH step compared to Pd/MnO; while conversely, the HCOOH → H 2 CO 3 step is more facilely accomplished over Pd/MnO. Furthermore, the nanoscale intimacy between two components enhances the mobility of lattice oxygen, thereby facilitating interfacial reconstruction and promoting interaction between active sites of Pd/Mn 3 O 4 and Pd/MnO in local vicinity, which further benefits sustained HCHO tandem catalytic oxidation. The tandem catalysis demonstrated in this work provides a generalizable platform for the future design of well-defined functional catalysts for oxidation reactions.

Light alkanes make up a class of widespread volatile organic compounds (VOCs), bringing great environmental hazards and health concerns. However, the low-temperature catalytic destruction of light alkanes is still a great challenge to settle due to their high reaction inertness and weak polarity. Herein, a Co 3 O 4 sub-nanometer porous sheet (Co 3 O 4 -SPS) was fabricated and comprehensively compared with its bulk counterparts in the catalytic oxidation of C 3 H 8 . Results demonstrated that abundant low-coordinated Co atoms on the Co 3 O 4 -SPS surface boost the activation of adsorbed oxygen and enhance the catalytic activity. Moreover, Co 3 O 4 -SPS has better surface metal properties, which is beneficial to electron transfer between the catalyst surface and the reactant molecules, promoting the interaction between C 3 H 8 molecules and dissociated O atoms and facilitating the activation of C-H bonds. Due to these, Co 3 O 4 -SPS harvests a prominent performance for C 3 H 8 destruction, 100% of which decomposed at 165 °C (apparent activation energy of 49.4 kJ mol -1 ), much better than the bulk Co 3 O 4 (450 °C and 126.9 kJ mol -1 ) and typical noble metal catalysts. Moreover, Co 3 O 4 -SPS also has excellent thermal stability and water resistance. This study deepens the atomic-level insights into the catalytic capacity of Co 3 O 4 -SPS in light alkane purification and provides references for designing efficacious catalysts for thermocatalytic oxidation reactions., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

Volatile organic amines are a category of typical volatile organic compounds (VOCs) extensively presented in industrial exhausts causing serious harm to the atmospheric environment and human health. Monometallic Pd and Cu-based catalysts are commonly adopted for catalytic destruction of hazardous organic amines, but their applications are greatly limited by the inevitable production of toxic amide and NO x byproducts and inferior low-temperature activity. Here, a CuO/Pd@SiO 2 core-shell-structured catalyst with diverse functionalized active sites was creatively developed, which realized the total decomposition of n -butylamine at 260 °C with a CO 2 yield and N 2 selectivity reaching up to 100% and 98.3%, respectively (obviously better than those of Pd@SiO 2 and CuO/SiO 2 ), owing to the synergy of isolated Pd and Cu sites in independent mineralization of n -butylamine and generation of N 2 , respectively. The formation of amide and short-chain aliphatic hydrocarbon intermediates via C-C bond cleavage tended to occur over Pd sites, while the C-N bond was prone to breakage over Cu sites, generating NH 2 · species and long free-N chain intermediates at low temperatures, avoiding the production of hazardous amide and NO x . The SiO 2 channel collapse and H + site production resulted in the formation of N 2 O via suppressing NH 2 · diffusion. This work provides critical guidance for a rational fabrication of catalysts with high activity and N 2 selectivity for environmentally friendly destruction of nitrogen-containing VOCs.

The evaluation of the poisoning effect of complex components in practical gas on DCM (dichloromethane) catalytic ozonation is of great significance for enhancing the technique's environmental flexibility. Herein, Ca, Pb, As, and NO/SO 2 were selected as a typical alkaline-earth metal, heavy metal, metalloid, and acid gas, respectively, to evaluate their interferences on catalytic behaviors and surface properties of an optimized urchin-like CuMn catalyst. Ca/Pb loading weakens the formation of oxygen vacancies, oxygen mobility, and acidity due to the fusion of Mn-Ca/Pb-O, leading to their inferior catalytic performance with poor CO 2 selectivity and mineralization rate. Noticeably, the presence of As induces excessively strong acidity, facilitating the inevitable formation of byproducts. Catalytic co-ozonation of NO/DCM is achieved with stoichiometric ozone addition. Unfortunately, SO 2 introduction brings irreversible deactivation due to strong competition adsorption and the loss of active sites. Unexpectedly, Ca loading protects active sites from an attack by SO 2 . The formation of unstable sulfites and the released Mn-O structure offset the negative effect from SO 2 . Overall, the catalytic ozonation of DCM exhibits a distinctive priority in the antipoisoning of metals with the maintenance of DCM conversion. The construction of more stable acid sites should be the future direction of catalyst design; otherwise, catalytic ozonation should be arranged together with post heavy metal capture and a deacidification system.

Developing economic and applicable catalysts with elegant chlorine resistance and organic byproduct inhibition capability is of great significance for chlorinated volatile organic compounds (Cl-VOCs) eco-friendly purification. Here, ternary Ce x Sr 1- x TiO 3 catalysts with tunable surface acidity and oxygen species mobility were creatively fabricated using the hollow tubular-structured fruit hair of Platanus (FHP; a widespread greenery waste) as the scaffolding biotemplate. It is shown that the oxygen vacancy (O v ) triggered by the presence of Ce can optimize the synergy between the Lewis acid sites (LAS) and Brønsted acid sites (BAS). High concentration of O v and BAS promotes the C-Cl cleavage of chlorobenzene (CB) and accelerates the desorption of Cl • radicals as inorganic chlorine. Simultaneously, the strong electron transfer within Ti-Ce-Sr linkage increases the acidity of LAS, resulting in the superior reducibility of Ce 0.4 Sr 0.6 TiO 3 and facilitating the deep oxidation of dechlorination intermediates. Additionally, the spatial confinement of the tubular structure remarkably accelerates the CB flow rate and reduces the residence time of byproducts over the prepared catalysts. Owing to these, CB can be efficiently destructed over Ce 0.4 Sr 0.6 TiO 3 with selectivity of CO 2 and inorganic chlorine dramatically enhanced, respectively, approximately 16 and 21 times at 275 °C compared to those of pure SrTiO 3 . The present work provides a feasible and promising strategy for engineering efficient catalysts for heterogeneous thermocatalytic reactions for industrial-scale Cl-CVOC destruction.

Achieving excellent efficiency to mineralize volatile organic compounds (VOCs) under nonthermal plasma catalysis (NTP-catalysis) systems tremendously relies on the catalyst design. Herein, we report a dual-template strategy for synthesizing a core-shell structured nitrogen-enriched hollow hybrid carbon (N-HHC) by a facile pyrolysis of a Mn-ZIF-8@polydopamine core-shell precursor. N-HHC exhibits a remarkable plasma synergy effect and superior degradation efficiency for toluene (up to 90% with a specific input energy of 281 J/L), excellent CO 2 selectivity (>45%), and byproduct-inhibiting capability. Such outstanding functionality of the developed N-HHC is uniquely attributed to its hollow multistage and channeling structure, high concentration of O 3 -decomposing species (pyrrolic and oxide pyridinic-N), and abundant ZnO active sites. Shedding light on an efficient synthetic strategy for designing an advanced nanocatalyst with enhanced VOC destruction in the NTP-catalysis system, the present results could be extended to design other N-doped metal/metal oxide-decorated hollow porous carbons for environment-related applications.

The site-specific oxidation of strong C(sp 3 )-H bonds is of uncontested utility in organic synthesis. From simplifying access to metabolites and late-stage diversification of lead compounds to truncating retrosynthetic plans, there is a growing need for new reagents and methods for achieving such a transformation in both academic and industrial circles. One main drawback of current chemical reagents is the lack of diversity with regard to structure and reactivity that prevents a combinatorial approach for rapid screening to be employed. In that regard, directed evolution still holds the greatest promise for achieving complex C-H oxidations in a variety of complex settings. Herein we present a rationally designed platform that provides a step toward this challenge using N -ammonium ylides as electrochemically driven oxidants for site-specific, chemoselective C(sp 3 )-H oxidation. By taking a first-principles approach guided by computation, these new mediators were identified and rapidly expanded into a library using ubiquitous building blocks and trivial synthesis techniques. The ylide-based approach to C-H oxidation exhibits tunable selectivity that is often exclusive to this class of oxidants and can be applied to real-world problems in the agricultural and pharmaceutical sectors.

The intriguing structure of tagetitoxin ( 1 ), a long-standing challenge in natural product synthesis, has been the subject of multiple revisions and has been confirmed through total synthesis. The route commences from a renewable furan starting material and features a number of unusual transformations (such as rearrangements, bromocyclization, and P(V)-based phosphate installation) to arrive at the target in 15 steps. As the route was designed to enable access to both enantiomers, the absolute configuration of the natural product could be assigned using a bioassay on (+)- 1 and (-)- 1 .

An asymmetric approach for the first total synthesis of (-)-rhodomollanol A, a highly oxidized diterpenoid, is described. The efficient synthetic strategy features three key transformations: (1) an oxidative dearomatization-induced (5 + 2) cycloaddition/pinacol-type 1,2-acyl migration cascade to build up the bicyclo[3.2.1]octane skeleton; (2) a retro -Dieckmann fragmentation/vinylogous Dieckmann cyclization cascade to assemble the bicyclo[3.3.0]octane subunit; and (3) a photo-Nazarov cyclization/intramolecular cycloetherification cascade to forge the 7-oxabicyclo[4.2.1]nonane core structure of the natural product.

Shape effects of nanocrystal catalysts in different reactions have attracted remarkable attention. In the present work, three types of α-Fe 2 O 3 oxides with different micromorphologies were rationally synthesized via a facile solvothermal method and adopted in deep oxidation of ethane. The physicochemical properties of prepared materials were characterized by XRD, N 2 sorption, FE-SEM, HR-TEM, FTIR, in situ DRIFTS, XPS, Mössbauer spectroscopy, in situ Raman, electron energy loss spectroscopy, and H 2 -TPR. Moreover, the formation energy of oxygen vacancy and surface electronic structure on various crystal faces of α-Fe 2 O 3 were explored by DFT calculations. It is shown that nanosphere-like α-Fe 2 O 3 exhibits much higher ethane destruction activity and reaction stability than nanocube-like α-Fe 2 O 3 and nanorod-like α-Fe 2 O 3 due to larger amounts of oxygen vacancies and lattice defects, which greatly enhance the concentration of reactive oxygen species, oxygen transfer speed, and material redox property. In addition to this, DFT results reveal that nanosphere-like α-Fe 2 O 3 has the lowest formation energy of oxygen vacancy on the (110) facet ( E vo (110) = 1.97 eV) and the strongest adsorption energy for ethane (-0.26 eV) and O 2 (-1.58 eV), which can accelerate the ethane oxidation process. This study has deepened the understanding of the face-dependent activities of α-Fe 2 O 3 in alkane destruction.

In the present work, a series of MOF-74 (Ni) materials with narrow micropore channels and abundant unsaturated metal sites was respectively prepared via hydrothermal (HT), condensation reflux (CE), and microwave-assisted (MW) methods. The physicochemical properties of synthesized materials were characterized by powder X-ray diffraction, N 2 -sorption, field-emission scanning electron microscopy, Fourier-transform infrared (FTIR), thermogravimetric (TG)/TG-FTIR, X-ray photoelectron spectroscopy, UV-vis-near infrared, NH 3 /CO 2 -temperature programmed desorption, and in situ diffuse reflectance infrared Fourier transform spectroscopy. Their CO 2 /N 2 adsorption performances were evaluated by isotherm adsorption and dynamic adsorption experiments. We found that the MW is a rapid and facile protocol for the synthesis of MOF-74 (Ni) materials with highly efficient CO 2 capture capacity. The well-shaped MW-140 adsorbent with superior CO 2 adsorption capacity of 5.22 mmol/g at 25 °C can be obtained within 60 min by the MW process, almost 6 times higher than that of the commercial activated carbon (0.89 mmol/g). Results of dynamic adsorption experiments showed that the MW-140 material possesses the highest CO 2 adsorption capacity of 3.37 mmol/g under humid conditions (RH = 90%). Importantly, MW-140 has excellent adsorption stability and recyclability, superior CO 2 capture selectivity (CO 2 /N 2 = 31), and appropriate isosteric heat in CO 2 adsorption (21-38 kJ/mol), making it a promising and potential material for industrial CO 2 capture. Characterization results demonstrated that the high capture capability of MOF-74 (Ni) materials can be attributed to the synergistic effect of abundant narrow micropore channels and rich five-coordinated Ni 2+ open metal sites which are beneficial for the trapping of CO 2 molecules.

Mn 3 O 4 , FeMnO x , and FeO x catalysts synthesized via a solvothermal method were employed for catalytic oxidation of methyl-ethyl-ketone (MEK) at low temperature. Mn 3 O 4 with sphere-like morphology exhibited the highest activity for MEK oxidation, over which MEK was completely oxidized to CO 2 at 200 °C, and this result can be comparable to typical noble metal loaded catalysts. The activation energy of MEK over Mn 3 O 4 (30.8 kJ/mol) was much lower than that of FeMnO x (41.5 kJ/mol) and FeO x (47.8 kJ/mol). The dominant planes, surface manganese species ratio, surface-absorbed oxygen, and redox capability played important roles in the catalytic activities of catalysts, while no significant correlation was found between specific surface area and MEK removal efficiency. Mn 3 O 4 showed the highest activity, accounting for abundant oxygen vacancies, low content of surface Mn 4+ and strong reducibility. The oxidation of MEK to CO 2 via an intermediate of diacetyl is a reaction pathway on Mn 3 O 4 catalyst. Due to high efficiency and low cost, sphere-shaped Mn 3 O 4 is a promising catalyst for VOCs abatement.

The unprecedented oxidative dearomatization-induced [5+2] cycloaddition/pinacol-type 1,2-acyl migration cascade efficiently generates a quaternary carbon center and assembles the highly oxygenated bicyclo[3.2.1]octane framework of ent-kaurene diterpenoids. By incorporation of the subsequent retro-aldol/aldol process and singlet oxygen ene reaction, this concise and convergent approach has enabled the first asymmetric total syntheses of pharicin A, pharicinin B, 7-O-acetylpseurata C, and pseurata C.