Efficient CO2 hydrogenation to formate with an iridium catalyst supported by a porous organic polymer containing an N-phenylpicolinamide motif

Abstract

Development of highly efficient catalysts for CO₂ hydrogenation is crucial for the utilization of CO₂. In this work, two novel heterogeneous porous organic polymer (POP)-supported iridium catalysts (Cat-1 and Cat-2) functionalized with an N-phenylpicolinamide motif were synthesized using a straightforward method. The structural modification of the picolinamide resulted in a higher proportion of micropores in the catalyst, which increased its affinity for CO₂ and further enhanced the catalytic performance. A high turnover number (TON) of 13 883 was achieved for CO₂ hydrogenation to formate with the catalyst Cat-2 in 2 h under 3 MPa (H₂/CO₂ = 1 : 1) at 120 °C in 2 M K₂CO₃ aqueous solution. Dynamics studies have shown that the heterolysis of H₂ is the rate-determining step. A reaction mechanism is proposed based on the experimental results and the characterization of the catalyst.