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 (CO 2 ) 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 (Ru 3+ -POPs@MHCS) is reported for CO 2 hydrogenation to formate. Based on comprehensive structural analyses, we demonstrated that Ru 3+ -POPs were successfully immobilized within MHCS. The optimized Ru 3+ -0.5POPs@MHCS catalyst, which was obtained with about 5 wt.% Ru 3+ and 0.5 mmol POPs polymers confined into 0.3 g MHCS, exhibited high catalytic activity for CO 2 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 Ru 3+ catalysts without POPs polymers (Ru 3+ -MHCS) and unencapsulated MHCS (Ru 3+ -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 Ru 3+ -POPs. Furthermore, the MHCS and POPs showed high CO 2 adsorption ability. Ru 3+ -POPs encapsulated into MHCS reduces the activation energy barrier for CO 2 hydrogenation to formate.