Rational Design of Synergistic Structure Between Single-Atoms and Nanoparticles for CO₂ Hydrogenation to Formate Under Ambient Conditions

Single-atom catalysts (SACs) as the new frontier in heterogeneous catalysis have attracted increasing attention. However, the rational design of SACs with high catalytic activities for specified reactions still remains challenging. Herein, we report the rational design of a Pd₁-Pd_NPs synergistic structure on 2,6-pyridinedicarbonitrile-derived covalent triazine framework (CTF) as an efficient active site for CO₂ hydrogenation to formate under ambient conditions. Compared with the catalysts mainly comprising Pd₁ and Pd_NPs, this hybrid catalyst presented significantly improved catalytic activity. By regulating the ratio of Pd₁ to Pd_NPs, we obtained the optimal catalytic activity with a formate formation rate of 3.66 mol_HCOOM·mol_Pd ^-1·h^-1 under ambient conditions (30°C, 0.1 MPa). Moreover, as a heterogeneous catalyst, this hybrid catalyst is easily recovered and exhibits about a 20% decrease in the catalytic activity after five cycles. These findings are significant in elucidating new rational design principles for CO₂ hydrogenation catalysts with superior activity and may open up the possibilities of converting CO₂ under ambient conditions.