Pd–Fe_xO_y Hybrid Nanoparticles Encaged Hollow Mesoporous Silica Nanoreactors for Reduction of Nitroarenes to Aminoarenes

In this work, Pd–Fe_xO_y hybrid nanoparticles encaged hollow mesoporous silica nanoreactors (Pd–Fe_xO_y@HMSNs) are synthesized, which features ∼3–4 nm Pd–Fe_xO_y hybrid nanoparticles inside ∼17 nm hollow cavities of ∼32 nm mesoporous silica nanoreactors. By employing Pd and Fe ions containing polymer micelles as templates for silica deposition, hollow mesoporous silica nanoreactors and the residence of functional nanoparticles inside hollow cavities are simultaneously obtained. Through adjusting the ratios of Pd²⁺/Fe³⁺ in micelles, various Pd–Fe_xO_y@HMSNs with different Pd/Fe ratios are synthesized and tested for reduction of nitroarenes with NaBH₄. Relative to Pd@HMSNs, Fe_xO_y@HMSNs and their physical mixtures, Pd₁–(Fe_xO_y)_1/x@HMSNs illustrate a greatly enhanced catalytic performance for reductions of a series of substituted nitroarenes with NaBH₄ to aminoarenes. The catalytic enhancement of Pd–Fe_xO_y@HMSNs is ascribed to the synergistic effect of Pd and Fe_xO_y as well as the confinement effect of functional nanoparticles inside hollow cavities.