Covalent organic frameworks based on tetraphenyl-p-phenylenediamine and metalloporphyrin for electrochemical conversion of CO2 to CO

Abstract

Electrocatalytic CO₂ reduction provides a possible method for carbon neutralization. Electrode materials with efficient electron transfer, high selectivity and large current density are highly desirable. Herein, we have developed a couple of tetraphenyl-p-phenylenediamine and metalloporphyrin-based 2D COFs for the electrocatalytic CO₂ reduction. TPPDA-MPor-COFs (M = Co and Ni) were obtained by the cross-condensation of tetraphenyl-p-phenylenediamine (TPPDA) and 5,10,15,20-tetrakis(4-formylphenyl)-metalloporphyrin (MPor). The as-prepared TPPDA-CoPor-COF shows high CO faradaic efficiencies of 87–90% from −0.6 to −0.9 V vs. RHE, and the largest CO partial current density (j_CO) of TPPDA-CoPor-COF (−22.2 mA cm⁻² at −1.0 V vs. RHE) exceeds those of most of the reported COF-based electrocatalysts. Notably, exfoliated TPPDA-CoPor-COF nanosheets (TPPDA-CoPor-COF-NSs) show much better electrocatalytic performance. The CO faradaic efficiencies of TPPDA-CoPor-COF-NSs are over 90% in a wider voltage range (−0.7 to −0.9 V), and the maximum j_CO reaches up to −29.2 mA cm⁻² at −1.0 V. Density functional theory calculations have been performed to rationalize the improved CO₂RR performance of TPPDA-CoPor-COF.