A benzimidazole-linked bimetallic phthalocyanine-porphyrin covalent organic framework synergistically promotes CO2 electroreduction

Bimetallic catalysts have recently emerged as promising candidates for CO2 reduction. However, it is still critical to strategically synthesize atomically precise bimetallic catalysts and clarify the interaction mechanism of bimetal sites. Herein, we connected the active metallic porphyrin and phthalocyanine moieties by the unique benzimidazole linkage to obtain a novel Ni,Co-based bimetallic covalent organic framework (denoted as NiPc-CoPor-imi-COF), for efficient electrocatalytic CO2 conversion. Compared with its monometallic Ni and Co counterparts, NiPc-CoPor-imi-COF with a synergistic effect exhibited much higher activity and selectivity with a maximum CO faradaic efficiency (FECO) of 97.1%. Mechanistic studies revealed that the efficient charge transport along the COF backbone promoted electronic communication between the bimetallic active sites and enabled regulation of the intrinsic activity of each catalytic center, namely improving the activity of Ni sites by promoting *COOH generation and optimizing the selectivity of Co sites by depressing *H formation, thus ultimately achieving high CO2 conversion efficiency. This work provides insights into synergistic catalysis with bimetallic sites for efficient CO2 reduction.

Automated summary

In this study, a novel Ni,Co-based bimetallic covalent organic framework (NiPc-CoPor-imi-COF) was synthesized by connecting metallic porphyrin and phthalocyanine moieties through a unique benzimidazole linkage. The NiPc-CoPor-imi-COF exhibited excellent activity and selectivity for electrocatalytic CO2 conversion, with a maximum CO faradaic efficiency (FECO) of 97.1%. Mechanistic studies revealed that efficient charge transport along the COF backbone promoted electronic communication between the bimetallic active sites, enabling regulation of the intrinsic activity of each catalytic center and achieving high CO2 conversion efficiency.