A Zn(II) Coordination Polymer as an Ultrastable Heterogeneous Photocatalyst for CO₂ Photoreduction with H₂O

Photoreduction of CO₂ into high value-added products offers a promising approach to mitigating the global energy crisis. Coordination polymers (CPs) show promising potential in CO₂ photoreduction due to their tunable structures. However, CP-based catalysts for CO₂ photoreduction are limited by their poor recyclability and weak light absorption. Here, we have designed a new Zn-based CP {Zn-CP: [Zn(Bipn)Br₂]_n}, via the self-assembly of Zn ions and Bipn [N,N'-bis(3-imidazol-1-ylpropyl)naphthalenediimide]. Zn-CP shows high reactivity toward CO₂ photoreduction with H₂O, mainly due to the strong wide light absorption and high photoelectric conversion ability of the large conjugated naphthalenediimide rings of Bipn. Most importantly, the evolution rate of CH₃OH (4.00 μmol g^-1 h^-1) is maintained after 10 photocatalytic cycles, while that of CO (45.28 μmol g^-1 h^-1) is maintained after 7 photocatalytic cycles and then significantly increased by ∼1.33 times for the next three photocatalytic cycles, demonstrating excellent catalytic stability of Zn-CP. The excellent recyclability of Zn-CP is much better than that of the most reported CP-based photocatalysts. The catalytic mechanism of Zn-CP toward CO₂ photoreduction has been proposed based on experimental data combining with the DFT-calculated results. This work offers a promising strategy for developing efficient and ultrastable CP-based photocatalysts for solar-driven CO₂ reduction.