Single Ru–P Site Catalyst Coupling N Sites in a Flexible Polymeric Framework for Efficient CO2 Hydrogenation to Formate

Hydrogenation of CO2, an abundant C1 resource, into formate, is one of the most charming utilization routes of CO2. Herein, a series of single Ru–P site catalysts coupling N sites (denoted as Ru/P&N-POPs) were designed and applied in the highly effective hydrogenation of CO2 to formate. The Ru (II) ions were firmly anchored and finely regulated by P sites in the polymeric skeleton, while the original N species surrounding single Ru–P active sites enriched and activated CO2. Besides, 13C{1H} R-type RF irradiation and two-dimensional separated local field (2D R-SLF) experiments proved the good flexibility of P&N-POPs frameworks, which were beneficial for optimizing the orientation of functional sites and the synergy of abundant Ru–P active species and N species. As a result, a ca. 2000 h–1 TOF of CO2 and at least 5 recycles were achieved in the formate synthesis under 393 K and 6.0 MPa (CO2/H2 = 1:1). Multiple characterization methods including mass nuclear magnetic resonance, extended X-ray absorption fine structure, scanning transmission electron microscopy, in situ Fourier transform infrared, etc. were employed to reveal the mechanism for the catalytic performance of Ru/P&N-POPs.