The synthesis of support materials with suitable coordination sites and confined structures for the controlled

growth of ultrasmall metal nanoparticles is of great importance in heterogeneous catalysis. Here, by rational

design of a cross-linked beta-cyclodextrin polymer network (CPN), various metal nanoparticles (palladium, silver,

platinum, gold, and rhodium) of subnanometer size (<1 nm) and narrow size distribution are formed via a mild

and facile procedure. The presence of the metal coordination sites and the network structure are key to the

successful synthesis and stabilization of the ultrasmall metal nanoparticles. The as-prepared CPN, loaded with

palladium nanoparticles, is used as a heterogeneous catalyst and shows outstanding catalytic performance in

the hydrogenation of nitro compounds and Suzuki-Miyaura coupling reaction under mild conditions. The CPN

support works synergistically with the metal nanoparticles, achieving high catalytic activity and selectivity. In

addition, the catalytic activity of the formed catalyst is controllable.