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.