Development of nickel-incorporated MCM-41–carbon composites and their application in nitrophenol reduction

Abstract

MCM-41–carbon composites were obtained by soft-templating strategy by adding resorcinol and formaldehyde as carbon precursors during the synthesis of MCM-41. The synthesis of these composites was optimized until mesoporous MCM-41 domains remained highly ordered and the overall specific surface area and pore volume remained relatively high. The one-pot synthetic procedure was further extended to obtain the Ni-containing MCM-41–carbon composites using nickel nitrate as an additive. A homogeneous distribution of nickel nanoparticles in the composites was achieved by adding histidine to the reaction mixture, which was able to form a complex with nickel ion. Carbonization of organic components in the composites produced carbon that was responsible for in situ reduction of nickel(II) to metallic nickel (Ni⁰) at elevated temperatures, eliminating the post-synthesis reduction step carried out in the presence of hydrogen gas or other reducing agent. The resulting composites showed enhanced catalytic activity toward nitrophenol reduction obeying the zero-order kinetics. Three unique features of the resulting composites, namely mesoporous channels of MCM-41, carbon-induced in situ reduction of Ni ions to metallic Ni nanoparticles, and abundance of highly active Ni sites due to high dispersion of Ni⁰, make this strategy applicable for the synthesis of other transition metal-based catalysts. XRD and STEM analyses revealed a homogeneous distribution of nickel nanoparticles in the composites without significant distortion of their ordered mesoporosity.