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Hollow mesoporous nanoreactors with encaged functional nanoparticles are promising heterogeneous catalysts due to the advantages related to their hollow cavities. In this study, we employ metal ion-bound polymer micelles to synthesize PtSn alloy nanoparticle-encaged hollow mesoporous nanoreactors (PtSn@HMSNs), which contain ∼4 nm PtSn alloy NPs located in ∼13 nm hollow cavities and relatively large (∼9 nm) mesoporous channels in silica shells. Relative to monometallic Pt@HMSNs and supported Pt 1 Sn 0.3 /SiO 2 , Pt 1 Sn 0.3 @HMSNs exhibit greatly enhanced activity and selectivity for hydrogenation of furfural to furfuryl alcohol. At 1.0 MPa H 2 , 100 °C, and a furfural/Pt molar ratio of 1884:1, 97.5% of furfuryl alcohol yield was achieved in 5.0 h. The dramatically promoted catalytic performance of Pt 1 Sn 0.3 @HMSNs can be assigned to the confinement effect that the location of active NPs inside hollow cavities increases the collision rates between reactants and active NPs to promote catalytic activity, as well as the synergistic effect between Pt and Sn.

PtRh bimetallic nanoparticle (NP)-encaged hollow mesoporous silica nanoreactors (PtRh@HMSNs) are prepared by employing metal-ion-containing charge-driven polymer micelles as templates. These nanoreactors feature ∼1−2 nm PtRh NPs in ∼11 nm hollow cavities of HMSNs. Among various Pt x Rh y @HMSNs, Pt 0.77 Rh 1 @HMSNs show the best catalytic performance for toluene hydrogenation. Under 30 °C, atmospheric H 2 pressure, and a toluene/(Pt+Rh) molar ratio of 200/1, Pt 0.77 Rh 1 @HMSNs reach 100.0% of methyl cyclohexane yield and demonstrate a much better catalytic performance than monometallic Pt@ HMSNs and Rh@HMSNs and their physical mixtures. Moreover, Pt 0.77 Rh 1 @HMSNs exhibit a good catalytic stability during recycling experiments. The enhanced performance of Pt 0.77 Rh 1 @HMSNs is ascribed to the interaction between Pt and Rh, the beneficial effect of the relatively large mesoporous channels for mass transfer, as well as the confinement effect of functional NPs inside hollow cavities.

In this work, Pd−Fe x O y hybrid nanoparticles encaged hollow mesoporous silica nanoreactors (Pd−Fe x O y @HMSNs) are synthesized, which features ∼3−4 nm Pd−Fe x O 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 Pd 2+ /Fe 3+ in micelles, various Pd−Fe x O y @HMSNs with different Pd/Fe ratios are synthesized and tested for reduction of nitroarenes with NaBH 4 . Relative to Pd@HMSNs, Fe x O y @HMSNs and their physical mixtures, Pd 1 −(Fe x O y ) 1/x @HMSNs illustrate a greatly enhanced catalytic performance for reductions of a series of substituted nitroarenes with NaBH 4 to aminoarenes. The catalytic enhancement of Pd−Fe x O y @HMSNs is ascribed to the synergistic effect of Pd and Fe x O y as well as the confinement effect of functional nanoparticles inside hollow cavities.

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