Size-Controlled Ni Nanoparticles Confined into Amino-Modified Mesoporous Silica for Efficient Hydrodeoxygenation of Bio-Derived Aromatic Aldehyde

For size-sensitive catalytic reaction systems, precise control of geometric size of heterogeneous transition metal catalysts, especially for non-noble metals, is in desperate need and also a great challenge. Here, highly dispersed Ni nanoparticles (NPs) anchored within mesoporous silica (MS) is fabricated through a hybrid strategy of amino-modification and vacuum-impregnation. The Ni NPs in Ni/MS catalyst can be precisely regulated from 2.2 to 12.6 nm, causing a variation in the proportion of low and high coordination sites of Ni atoms. The Ni/MS catalysts show a volcanic trend between 2-methoxy-4-methylphenol (MMP) yield and Ni geometry size in hydrodeoxygenation (HDO) of bio-derived vanillin, and the Ni/MS-4.8 catalyst with middle size (4.8 nm) shows optimal HDO performance with the highest MMP productivity of 19.5 g MMP g Ni −1 h −1 . DFT calculation demonstrates that the medium-sized Ni/MS-4.8 catalyst possesses abundant low/high coordinated Ni atoms, wherein the low coordinated Ni atoms facilitate the adsorption of H 2 and vanillin, and the high coordinated Ni atoms promote the dissociation of H 2 and activating of C═O and C─O bonds, thus displays superior performance in HDO reaction. This work paves a way in precise control of geometric size of heterogeneous catalysts applicating in size-sensitive catalysis.