Hollow metal nanoparticles have attracted great interest in heterogeneous catalysis research due to their unique structures as nanoreactors. Here, we report hollow PtCu nanoparticles encapsulated in microporous silica shells ([email protected]2), which can serve as the nanoreactor with high catalytic activity and high stability. The [email protected]2 nanoreactor shows the state-of-the-art catalytic performance for the transfer hydrogenation of benzonitrile to dibenzylamine, which achieves up to 100% conversion and 99% selectivity in only 0.5 h. The void-confinement effect of [email protected]2 is crucial for the outstanding catalytic performance by encaging the reactants in the nanoreactor. The computation demonstrates the limiting diffusion effect of the silica shell toward the ammonia borane, thus reduces the concentration of reductant species and prolongs the lifetime of the intermediate imine to improve the selectivity of secondary amine. Moreover, the silica shells can effectively enhance the catalytic stability of the [email protected]2 nanoreactor.