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The availability of catalytic sites for contact with reactants is a key issue to improve the performance of a catalyst, where constructing hollow structured nanomaterials has been considered as an effective strategy. Here, an N-doped carbon supported Ru catalyst with an interior cavity was synthesized by etching a MOF-derived core–shell precursor, in which metal Ru can be highly dispersed in the porous shell. This catalyst shows 98.7% conversion and >99% selectivity towards p-chloroaniline in the hydrogenation of p-chloronitrobenzene, which is better than the corresponding supported catalyst. Moreover, it also displays excellent stability with 5 cycle runs and good substrate universality for the hydrogenation of extensive substituted nitroarenes. Various characterization techniques and control experiments reveal the advantage of the unique structure to promote the mass transport and adsorption of reactant molecules on Ru sites. This work provides a novel strategy to design an efficient Ru-based catalyst for chemoselective hydrogenation. [ABSTRACT FROM AUTHOR]

In this work, three commercial Cu catalysts were benchmarked in the CO2RR using a gas-diffusion type microfluidic flow electrolyzer. We showed that commercial Cu could deliver a high FE of near 80% for C2+ product formations at 300 mA cm−2. By tuning the catalyst loading, a high reaction rate of near 1 A cm−2 with a C2+ product FE over 70% was achieved. Our results demonstrated that commercial Cu could achieve similar or better performances compared to many current catalysts by design in the CO2RR using similar electrolyzers. In addition, we showed that high CO reduction reaction (CORR) performance could also be achieved on commercial Cu, and disparities between CO and CO2 electrolysis were discussed. [ABSTRACT FROM AUTHOR]

In this paper, the effects of Zr, Al or Sr doped Mn/MCM-41 on NH3-SCR activity, SO2/H2O resistance and mechanism were studied. The results showed that Mn/Zr-MCM-41 has 100% NOx conversion at 175–300 °C while Mn/Al-MCM-41 achieves about 94% N2 selectivity at 120–400 °C. Zr doping significantly enhances the resistance to SO2 at 200 °C while Sr plays a negative role. Doped metal does not change the ordered hexagonal arrangement of MCM-41, but can cause the specific surface area enrichment of Mn while Al doping leads to the entry of Mn into the channel of MCM-41. Mn/MCM-41 has only Lewis acid sites, but Zr, Al or Sr doped catalysts have Lewis and Brønsted acid sites. Moreover, the reaction path on Mn/MCM-41 and Mn/Zr-MCM-41 mainly conforms to the L–H mechanism while Mn–Al or Mn–Sr doped catalysts follow L–H and E–R mechanisms. However, the deposited sulfates change the progress of the NH3-SCR process and cause a decline of SCR activity. [ABSTRACT FROM AUTHOR]

A Co–zeolite imidazole ester framework (ZIF-67) has excellent electrochemical performance for the oxygen reduction reaction (ORR), but the structural stability is still the key problem to be solved. PEDOT is a polymer of EDOT (3,4-ethylenedioxythiophene monomer), a π-conjugated conductive polymer with superior performance and wide application. It has a rigid and linear conformation, which is necessary to maintain the integrity of the material structure and prevent collapse. And this conformation is also conducive to charge transport and crystallization, resulting in good performance of high charge/discharge capacities, fast response time and high sensing ability. Herein through the pre-implantation of PEDOT nanowires, the structural collapse, anisotropic shrinkage and Co atom agglomeration of ZIF-67 in the pyrolysis process were inhibited, and S,N co-doping was realized at the same time. The XRD, SEM, TEM and XPS characterization studies prove that PEDOT nanowires successfully embedded in the ZIF-67 structure, and N and S are doped into the carbon framework of the catalyst. The synthesized catalyst has a regular hexahedral morphology, interconnected three-dimensional (3D) nanowire (NW) framework and graphitized carbon coated Co nanoparticles (Co/C@NS NWs), endowing it with excellent bifunctional catalytic performance toward oxygen. The initial potential was 0.91 V (vs. RHE) and the limiting current density was −4.8 mA cm−2 for the ORR. The potential required to reach 10 mA cm−2 is only 1.55 V (vs. RHE) and the Tafel slope for the oxygen evolution reaction (OER) is relatively low (100 mV dec−1). An open circuit voltage of 1.46 V for Zn–air battery cathodes catalyzed by Co/C@NS NWs at a discharge power density of 129.3 mWcm−2 is obtained, and the specific capacity at a discharge current density of 10 mA cm−1 is 800 mA h gZn−1. The voltages show no obvious change for a 35 h continuous discharge/charge cycle experiment. Therefore, this work provides a new inspiration for the design and development of high-performance non-noble metal carbon-based bifunctional oxygen electrocatalysts. [ABSTRACT FROM AUTHOR]

In the electrocatalytic CO2 reduction reaction (CO2RR), metal catalysts with an oxidation state generally demonstrate more favorable catalytic activity and selectivity than their corresponding metallic counterparts. However, the persistence of oxidative metal sites under reductive potentials is challenging since the transition to metallic states inevitably leads to catalytic degradation. Herein, a thorough review of research on oxidation-state stabilization in the CO2RR is presented, starting from fundamental concepts and highlighting the importance of oxidation state stabilization while revealing the relevance of dynamic oxidation states in product distribution. Subsequently, the functional mechanisms of various oxidation-state protection strategies are explained in detail, and in situ detection techniques are discussed. Finally, the prevailing and prospective challenges associated with oxidation-state protection research are discussed, identifying innovative opportunities for mechanistic insights, technology upgrades, and industrial platforms to enable the commercialization of the CO2RR. [ABSTRACT FROM AUTHOR]

The stability of Rh-based heterogeneous catalysts is a key issue in the hydroformylation of olefins. Confinement of active Rh species has been considered an effective strategy to achieve stable catalysts. In this work, a phosphine ligand was successfully confined in ZIF-8 material and coordinated with Rh metal by a reduction procedure to develop an efficient and stable Rh-based catalyst for hydroformylation of 1-octene. The results indicate that the catalyst reduced at 300 °C under H2 atmosphere exhibits better stability than that with NaBH4 as reductant and undoped P catalyst. Various characterization studies demonstrate that the superior performance is due to the strong interaction between Rh metal and P, which inhibits the leaching of active Rh species. This work reveals an effective strategy for the synthesis of highly stable catalysts for use in the hydroformylation reaction. [ABSTRACT FROM AUTHOR]

Microwave assisted lignin depolymerization was investigated over HSZ-supported CuNiAl-based catalysts. The synergistic effect between the acidic HSZ support and mixed metal oxides was studied in detail to explore the difference in catalytic activity during the lignin depolymerization process. Improvements in bio-oil properties, such as the H/C ratio and HHV value, were observed in comparison with raw lignin under rather mild conditions (140 °C, 80 min) in the absence of external hydrogen. The molecular weight of bio-oil obtained over HSZ-supported catalysts decreased, indicating that the increased acidity in the catalyst could facilitate microwave assisted lignin depolymerization. The product distributions in bio-oil were also analyzed and plausible depolymerization mechanisms were proposed considering the distributions of lignin-derived dimers/trimers and monomers. [ABSTRACT FROM AUTHOR]

Co, N co-doped carbon (CoN@C) with properly engineered heteropores was facilely synthesized using metal carbonate hydroxides as metal precursor and multistage porogen. CoN@C therefore exhibits superior ORR catalytic activity with a half-wave potential of 0.876 V vs. RHE, and the CoN@C-based zinc-air battery can be stably cycled for 100 h. [ABSTRACT FROM AUTHOR]

A facile boron doping strategy to improve the nitrogen retention in carbon-based catalysts is developed toward efficient oxygen reduction reaction via offsetting the electron migration. By considering the hetero-porous structure at the same time, this B, N co-doped catalyst outperforms commercial Pt/C in terms of both activity and stability. [ABSTRACT FROM AUTHOR]

Deoxygenation of fatty acids into liquid hydrocarbons is an efficient method of producing second-generation biofuels from biomass. Herein, we report efficient upgrading of stearic acid into a long-chain hydrocarbon at relatively low reaction temperature (140–220 °C) over a commercial Ru/C catalyst. The conversion process is predominantly through the hydrodecarboxylation pathway and not hydrodeoxygenation since heptadecane and not octadecane is found as the main product with the detection of CO2 in the gaseous products. The effects of process parameters including the solvent type (hexane, dodecane, isopropanol, water, and solvent-free), solvent volume, hydrogen pressure, catalyst loading, mass of feedstock, reaction temperature and reaction time on the conversion of stearic acid were systematically studied and optimized and the reusability of the catalyst was also studied. Hexane is found to be the most suitable solvent for the catalytic system. Under the optimized reaction conditions, 100% stearic acid conversion can be achieved at even 160 °C alongside a 90.1% yield of heptadecane. The apparent activation energy of the hydrodecarboxylation process over the commercial Ru/C catalyst was calculated to be 58.6 kJ mol−1. Notably, the reusability potential of the Ru/C catalyst is slightly limited by the accumulation of carbon deposits across multiple usage cycles. [ABSTRACT FROM AUTHOR]

A catalyst-controlled switch of regioselectivity in asymmetric allylic alkylation of oxazolones with MBHCs was described. The SN2′–SN2′ reaction catalysed by a quinine-derived base produced γ-selective secondary allylic oxazolone derivatives, whereas the addition–elimination reaction catalysed by an amino acid-derived bifunctional urea catalyst provided β-selective primary adducts. [ABSTRACT FROM AUTHOR]

An efficient catalyst based on the cage-like mesoporous material SBA-16 as the support and Cu(i) as active sites has been successfully prepared. The catalyst demonstrated high catalytic activity (up to 88%) in the direct oxidative synthesis of α-ketoamides between acetophenone and piperidine, employing O2 from open air as the oxidant without other additives. A heterogeneous catalyst was applied in this reaction for the first time, and the catalyst could be easily separated from the reaction system by filtration and reused several times without a significant loss of activity. [ABSTRACT FROM AUTHOR]