Facile　fabrication　of　nanocatalysts　consisting　of　metal　nanoparticles　(NPs)　anchored　on　a　functional　support　is　highly　desirable,　yet　remains　challenging.　Covalent　organic　frameworks　(COFs)　provide　an　emerging　materials　platform　for　structural　control　and　functional　design.　Here,　a　facile　one-pot　in　situ　reduction　approach　is　demonstrated　for　the　encapsulation　of　small　Pd　NPs　into　the　shell　of　COF-derived　hollow　polyamine　spheres　(Pd@H-PPA).　In　the　one-pot　synthetic　process,　the　nucleation　and　growth　of　Pd　NPs　in　the　cavities　of　the　porous　shell　take　place　simultaneously　with　the　reduction　of　imine　linkages　to　secondary　amine　groups.　Pd@H-PPA　shows　a　significantly　enhanced　catalytic　activity　and　recyclability　in　the　tandem　dehydrogenation　of　ammonia　borane　and　selective　hydrogenation　of　nitroarenes　through　an　adsorption–activation–reaction　mechanism.　The　strong　interactions　of　the　secondary　amine　linkage　with　borane　and　nitroarene　molecules　afford　a　positive　synergy　to　promote　the　catalytic　reaction.　Moreover,　the　hierarchical　structure　of　Pd@H-PPA　allows　the　accessibility　of　active　Pd　NPs　to　reactants.　©　2019　Wiley-VCH　Verlag　GmbH　&　Co.　KGaA,　Weinheim