Robust mesoporous two-dimensional covalent organic frameworks enabled by biphenyl-porphyrin for accelerated CO2 electroreduction

Covalent organic frameworks (COFs) incorporating metalloporphyrin units have gained significant attention as electrocatalysts for CO 2 reduction. However, conventional phenylporphyrin-based COFs are fundamentally limited by narrow pore sizes (<3 nm), which impose severe mass transfer resistance and impede catalytic turnover. Herein, we report a biphenyl porphyrin-based COF (DpPor-COF) with an expanded pore size of ∼3.8 nm, constructed from 5,10,15,20-tetra(4-formylbiphenyl)porphyrin and p -phenylenediamine. Subsequent metallation with Fe 3+ , Co 2+ , and Ni 2+ furnishes atomically dispersed M–N 4 sites (M-DpPor-COF), effectively suppressing metal leaching while expanding the electrochemical active surface area. Among the series, Co-DpPor-COF delivers a CO Faradaic efficiency (FE CO ) of 94% at −0.65 V vs. RHE with a high turnover frequency (TOF) of 477 h −1 , and maintains stable operation over 120 h. In situ infrared spectroscopy and DFT calculations reveal that transition metal centers lower the energy barrier for key intermediate steps in CO 2 -to-CO conversion, enhance charge density at the porphyrin core, and facilitate CO desorption. This work establishes a versatile strategy for concurrent pore engineering and active-site optimization, offering valuable insights for designing next-generation porous electrocatalysts. A biphenyl-porphyrin COF with an expanded 3.8 nm pore size is synthesized via the condensation of 5,10,15,20-tetra(4-formylbiphenyl)porphyrin and p -phenylenediamine, followed by metalation to introduce atomically dispersed M-N 4 sites, which delivers 94% CO Faradaic efficiency, 477 h −1 TOF and 120 h stability for efficient CO 2 electroreduction. Download: Download high-res image (175KB) Download: Download full-size image