Decarboxylation-Induced Defects in MOF-Derived Ni@C Catalysts for Efficient Chemoselective Hydrogenation of Nitrocyclohexane to Cyclohexanone Oxime

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, Ni@DC-0.06 gives 97.2% selectivity to CHO at 95.2% NCH conversion.