Ru complex and N, P-containing polymers confined within mesoporous hollow carbon spheres for hydrogenation of CO2 to formate

The development of reliable catalysts with both excellent activity and recyclability for carbon dioxide (CO2) hydrogenation is challenging. Herein, a ternary hybrid heterogeneous catalyst, involving mononuclear Ru complex, N, P-containing porous organic polymers (POPs), and mesoporous hollow carbon spheres (Ru3+-POPs@MHCS) is reported for CO2 hydrogenation to formate. Based on comprehensive structural analyses, we demonstrated that Ru3+-POPs were successfully immobilized within MHCS. The optimized Ru3+-0.5POPs@MHCS catalyst, which was obtained with about 5 wt.% Ru3+ and 0.5 mmol POPs polymers confined into 0.3 g MHCS, exhibited high catalytic activity for CO2 hydrogenation to formate (turnover number (TON) > 1,200 for 24 h under mild reaction conditions (4.0 MPa, 120 °C)) and improved durability, compared to Ru3+ catalysts without POPs polymers (Ru3+-MHCS) and unencapsulated MHCS (Ru3+-0.5POPs) catalysts. The improved catalytic performance is attributed to the high surface area and large pore volume of MHCS which favors dispersion and stabilization of Ru3+-POPs. Furthermore, the MHCS and POPs showed high CO2 adsorption ability. Ru3+-POPs encapsulated into MHCS reduces the activation energy barrier for CO2 hydrogenation to formate.