Confinement of Cu nanoparticles in the nanocages of large pore SBA-16 functionalized with carboxylic acid: Enhanced activity and improved durability for 4-nitrophenol reduction

Carboxylic acid (-COOH) functionalized large pore mesoporous silica SBA-16 is prepared and utilized as the support to synthesize Cu nanoparticles (NPs). The interaction between the -COOH groups in the support and the metal precursors effectively controls the dispersion and size of the Cu NPs. The Cu NP encapsulated large pore SBA-16 is used as a catalyst for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). The catalyst shows an excellent reaction rate of 1.55 × 10^-2 s^-1 and an outstanding activity of 950 s^-1 g^-1. The prominent catalytic activity can be attributed to the nanoscale dimension of the Cu NPs (ca. 5 nm) and their homogeneous distribution, and the 3D pore architecture of the support that allows easy transportation of the reactants. The cage-type mesopores of the support SBA-16 also effectively prevent aggregation and leaching of Cu NPs, and thus exhibit similar catalytic activity for several cycles, indicative of its superb durability.