Decarboxylation-Induced Defects in MOF-Derived Ni@C Catalysts for Efficient Chemoselective Hydrogenation of Nitrocyclohexane to Cyclohexanone Oxime
Pei Yuan, Xiaoqing Liao, Haishuai Cui, Fang Hao, Wei Xiong, He’an Luo, Yang Lv, Pingle Liu
Abstract
In this work, MOF-derived Ni@C catalysts with rich defects were synthesized using a facile thermally decarboxylation-induced defect strategy for nitrocyclohexane (NCH) hydrogenation. It was found that the strong metal–support interaction (SMSI) between the defect-rich carbon and Ni promotes the dispersion of Ni nanoparticles, reduces the Ni particle size, and affects the surface charge state of Ni to form electron-deficient Ni, thus exhibiting outstanding catalytic activity. Additionally, in situ diffuse reflectance infrared Fourier transform spectroscopy ( in situ DRIFTS) illustrates that the transformation path of nitrosocyclohexane (N-NCH) is critical for obtaining high selectivity to cyclohexanone oxime (CHO). Furthermore, the density functional theory (DFT) calculations confirm that the SMSI between the defect-rich carbon and Ni leads to the formation of electron-deficient Ni with a lower d-band center, which can weaken the adsorption of N-NCH and CHO, enhance the adsorption of N-cyclohexylhydroxylamine (N-CHH) and cyclohexylamine (CHA), reduce the reaction energy of the N-NCH to CHO, and increase the reaction energy of the N-NCH to CHA, thus showing the highest selectivity to CHO. Under optimum conditions, [email protected] gives 97.2% selectivity to CHO at 95.2% NCH conversion.