Highly dispersed Pd nanoclusters anchored on CNx-modified SiO2 for selective hydrogenation of nitrile-butadiene rubber

Heterogeneous hydrogenation is an effective way to improve the performance of unsaturated polymers, but the preparation of supported catalysts with high metal dispersion and stability remains challenging. Herein, we synthesize a SiO 2 -based support wrapping with carbon nitride on the surface (CN x @SiO 2 ) via the thermal polycondensation of melamine, on which Pd nanoclusters with highly exposed active sites are formed and stably anchored via the strong interaction between N and Pd. The thermal temperature affects the properties of CN x , which further modulates the electronic and structural state of Pd nanoclusters. The Pd/CN x @SiO 2 -500 catalyst, prepared at 500 °C with an optimal CN x structure ( g -C 3 N 4 ) and high nitrogen content, features highly dispersed and electron-rich Pd nanoclusters (1.3 nm). This catalyst exhibits a hydrogenation activity of 98.0% for nitrile rubber, with a selectivity of 100% for C=C bonds. This work provides a facile method to prepare Pd catalysts with high activity and stability, paving the way for the upgrading of unsaturated polymers via hydrogenation. Graphical abstract