Hyper-cross-linked polymer supported rhodium: an effective catalyst for hydrogen evolution from ammonia borane

Metal nanoparticles (NPs) have wide applications in hydrogen evolution from ammonia-borane (AB) hydrolysis because they can provide large surface active areas for reactants, and thus produce high catalytic activity. Here, a hyper-cross-linked polymer (HCP-PPh3), which was synthesized through the Friedel-Crafts reaction of benzene and triphenylphosphine, was employed as a support to stabilize Rh NPs. The characterization results revealed that the Rh NPs were uniformly dispersed on the surface of HCP-PPh3, and that they had an average particle size of 2.1 nm. The as-prepared HCP-PPh3-Rh was used as an active catalyst for hydrogen generation from AB hydrolysis. This catalyst exhibited a high turnover frequency of 481 mol H-2 (mol(Rh) min)(-1) for AB hydrolysis under mild conditions. The high catalytic performance of HCP-PPh3-Rh can be attributed to the small size of Rh NPs and the strong interaction between the metal and HCP-PPh3. This work highlights a potentially powerful strategy for preparing highly active HCP stabilized metal NPs for AB hydrolysis to generate hydrogen.