Porous Silica Nanoreactors Encapsulating Pd-SnOx Hybrid Nanostructures for the Catalytic Reduction of 4-Nitrophenol

Abstract

The synergy between noble metals and metal oxides can effectively improve the catalytic hydrogenation performance. However, precisely controlling the metal–metal oxide interaction remains a significant challenge. In this study, well-defined Pd-SnO_x hybrid nanostructures encapsulated in porous silica nanoreactors (Pd-SnO_x@pSiO₂) were prepared using a microemulsion system comprising water, cetyltrimethylammonium bromide (CTAB), and 1-dodecanethiol (C₁₂–SH). Within the system, CTAB and C₁₂–SH acted as co-surfactants, forming self-assembled micelles, with Pd and Sn ions coordinated to C₁₂–SH. Compared with individual Pd@pSiO₂, Pd₁-(SnO_x)_0.75@pSiO₂ exhibited significant improvements in catalytic efficient and stability (6 cycles, conversion >99, and 100% selectivity) for the catalytic reduction of 4-nitrophenol. This improvement is ascribed to the synergy between Pd and SnO_x, along with the confinement effect provided by the porous silica shells. This research provides a strategy for constructing reactive and stable noble-metal-based catalysts for the hydrogenation of substituted nitroaromatics.