An Intriguing Window Opened by Metallic Two-Dimensional Lindqvist-Cobaltporphyrin Organic Framework as an Electrochemical Catalyst for CO2 Reduction Reaction

Adequate studies have confirmed that polyoxometalates (POMs) are preeminent multi-electron donors and metalloporphyrins are electrochemically-generated active catalysts for CO2 reduction reaction. Integrating electron-rich POMs with metalloporphyrins in a metallic and stable organic framework can create facile and fascinating heterogeneous electrochemical catalysts by merging their complementary advantages and extensive promising possibilities. Herein, we designed and screened a series of stable and metallic two-dimensional (2D) polyoxometalate-metalloporphyrin organic frameworks (TM-PMOFs, TM in porphyrin = Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, Os, Ir, Pt) constructed by linking reductive Lindqvist-type hexamolybdate ([Mo6]2e/2H) with 4-connected tetra-(4-aminophenyl) metalloporphyrin (TM-TAPP) building structs through the Mo≡N triple bond, whose CO2 electrochemical reduction performances and processes are studied in detail by means of density functional theory (DFT). Our computations reveal that the Lindqvist-type clusters [Mo6]2e/2H act as multi-electronic regulators for reduction reaction, and then the most promising catalyst from CO2 to CH4 performs with the lowest theoretical driven potential (0.41 V). Moreover, the [Mo6]2e/2H units inside are easily reduced from the [Mo6] with a driven potential (0.08 V). Our work will encourage more experimental studies to further explore metallic 2D PMOF materials for CO2 electrochemical reduction.