Constant CO(x)-free H2 production from the catalytic decomposition of ammonia could be achieved over a high-surface-area molybdenum carbide catalyst prepared by a temperature-programmed reduction-carburization method. The fresh and used catalyst was characterized by N2 adsorption/desorption, powder X-ray diffraction, scanning and transmission electron microscopy, and electron energy-loss spectroscopy at different stages. Observed deactivation (in the first 15 h) of the high-surface-area carbide during the reaction was ascribed to considerable reduction of the specific surface area due to nitridation of the carbide under the reaction conditions. Theoretical calculations confirm that the N atoms tend to occupy subsurface sites, leading to the formation of nitride under an NH3 atmosphere. The relatively high rate of reaction (30 mmol/((g of cat.) min)) observed for the catalytic decomposition of NH3 is ascribed to highly energetic sites (twin boundaries, stacking faults, steps, and defects) which are observed in both the molybdenum carbide and nitride samples. The prevalence of such sites in the as-synthesized material results in a much higher H2 production rate in comparison with that for previously reported Mo-based catalysts.

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The structure–performance relationship is a critical fundamental issue in heterogeneous catalysis, and the size-dependent structure sensitivity of catalytic reactions has long been researched in catalysis. Yet it remains elusive for most of the reactions in a full-size range, from a single atom and subnanometer clusters to nanoparticles. Herein, we report complete size dependence of Pt catalysts used in propane dehydrogenation in terms of activity, selectivity, and stability due to coke formation. The turnover frequency (TOF) of the atomically dispersed Pt/Al2O3 catalyst was approximately 3-fold and 7-fold higher than the subnanometer-sized clusters and the nanoparticles, respectively. A canyon- shaped size dependence of the propene selectivity was observed with a bottom at about 2 nm of Pt particle size. The subnanometer-sized clusters have opposite size dependence of the propene selectivity compared to nanoparticles. Both atomically dispersed Pt and large Pt nanoparticles possess high propene selectivity. The atomically dispersed platinum centers with a positive charge dramatically enhanced the activity, weakened propylene adsorption, and prevented its deep dehydrogenation. Besides, the absence of multiple Pt–Pt sites effectively inhibited undesired side reactions (e.g., C–C cracking), thus improved propylene selectivity and stability. This work demonstrates the promising application of a supported atomically dispersed Pt catalyst for highly selective dehydrogenation of propane.

The development of noble-metal-free heterogeneous catalysts is promising for selective oxidation of aromatic alcohols;h owever,t he relatively lowc onversion of non-noble metal catalysts under solvent-free atmospheric conditions hinders their industrial application. Now,aholey lamellar high entropyoxide (HEO) Co 0.2 Ni 0.2 Cu 0.2 Mg 0.2 Zn 0.2 Omaterial with mesoporous structure is prepared by an anchoring and merging process.The HEO has ultra-high catalytic activity for the solvent-free aerobic oxidation of benzyl alcohol. Up to 98 %conversion can be achieved in only 2h,toour knowledge, the highest conversion of benzyl alcohol by oxidation to date. By regulating the catalytic reaction parameters,benzoicacid or benzaldehyde can be selectively optimizedasthe main product. Analytical characterizations and calculations provide adeeper insight into the catalysis mechanism, revealing abundant oxygen vacancies and holey lamellar framework contribute to the ultra-high catalytic activity.

An unprecedented gold-catalyzed formal [3+2] cycloaddition between ynamides and isoxazoles has been developed, allowing rapid and practical access to a wide range of synthetically useful 2-aminopyrroles.

A series of imidazolium-based ILs were supported on FDU-15 mesopolymer with abundant phenolic OH groups, which proved to be highly efficient and recyclable for the cycloaddition of CO2 with epoxides.

Achieving a selective 2 e À or 4 e À oxygen reduction reaction (ORR) is critical but challenging. Herein, we report controlling ORR selectivity of Co porphyrins by tuning only steric effects. We designed Co porphyrin 1 with meso-phenyls each bearing a bulky ortho-amido group. Due to the resulted steric hinderance, 1 has four atropisomers with similar electronic structures but dissimilar steric effects. Isomers abab and aaaa catalyze ORR with n = 2.10 and 3.75 (n is the electron number transferred per O 2 ), respectively, but aabb and aaab show poor selectivity with n = 2.89-3.10. Isomer abab catalyzes 2 e À ORR by preventing a bimolecular O 2 activation path, while aaaa improves 4 e À ORR selectivity by improving O 2 binding at its pocket, a feature confirmed by spectroscopy methods, including O K-edge near-edge X-ray absorption fine structure. This work represents an unparalleled example to improve 2 e À and 4 e À ORR by tuning only steric effects without changing molecular and electronic structures.

The direct oxidative dehydrogenation of lactates with molecular oxygen is a “greener” alternative for producing pyruvates. Here we report a one-pot synthesis of mesoporous vanadia–titania (VTN), acting as highly efficient and recyclable catalysts for the conversion of ethyl lactate to ethyl pyruvate. These VTN materials feature high surface areas, large pore volumes, and high densities of isolated vanadium species, which can expose the active sites and facilitate the mass transport. In comparison to homogeneous vanadium complexes and VOx/TiO2 prepared by impregnation, the meso-VTN catalysts showed superior activity, selectivity, and stability in the aerobic oxidation of ethyl lactate to ethyl pyruvate. We also studied the effect of various vanadium precursors, which revealed that the vanadium-induced phase transition of meso-VTN from anatase to rutile depends strongly on the vanadium precursor. NH4VO3 was found to be the optimal vanadium precursor, forming more monomeric vanadium species. V4+ as the major valence state was incorporated into the lattice of the NH4VO3-derived VTN material, yielding more V4+–O–Ti bonds in the anatase-dominant structure. In situ DRIFT spectroscopy and density functional theory calculations show that V4+–O–Ti bonds are responsible for the dissociation of ethyl lactate over VTN catalysts and for further activation of the deprotonation of β-hydrogen. Molecular oxygen can replenish the surface oxygen to regenerate the V4+–O–Ti bonds.