Electron-Rich Pincer Ligand-Coupled Cobalt Porphyrin Polymer with Single-Atom Sites for Efficient (Photo)Electrocatalytic CO Reduction at Ultralow Overpotential.

Porphyrin and phthalocyanine complexes bearing single-atom catalytic sites (M-N ) have been explored as promising electrocatalysts for CO reduction reaction (CO RR), whose activity can be improved by regulating the ligands and/or the metal centers. Moreover, their photosensitive features also provide the possibility for highly efficient photoelectrocatalytic CO RR. Herein, a novel N'NN'-pincer-ligand (N )-coupled cobalt porphyrin (CoPor-N ) polymer is developed for realizing efficient (photo)electrocatalytic CO RR. The unraveled electronic structure and (photo)electrocatalytic features suggest that a synergistic effect between the electron-rich N ligands and the Co-N single-atom sites in the CoPor-N polymer results in the Co centers attaining more electrons, which is beneficial to facilitating the electron transfer to CO for the activation and reduction processes. As expected, the resultant CoPor-N polymer delivers a good long-term durability and high CO faradaic efficiency (96%) at an ultralow overpotential (0.39 V), which outperforms the CoPor alone and most porphyrin-/phthalocyanine-based electrocatalysts reported so far. Moreover, the photosensitivity of CoPor units can further reduce the overpotential to 0.34 V with a CO faradaic efficiency over 90% under light illumination. The present findings offer a new approach to constructing porphyrin-based photosensitive electrocatalysts with high-efficiency photoelectrocatalytic CO RR.