Assembly and electrocatalytic CO2 reduction of two-dimensional bimetallic porphyrin-based conjugated cobalt metal-organic framework

Abstract

Electrocatalytic reduction of CO2 (CO2RR) into value-added chemicals is a promising approach to alleviate environmental issue, but the efficiencies of electrocatalysts are limited by the poor conductivity, low current density and large overpotential. Herein, two-dimensional bimetallic porphyrin-based conjugated cobalt MOF (Co-(Co+Cu) PMOF) is deposited on g-C3N4 nanosheets to construct g-C3N4@Co-(Co+Cu)PMOF which enhances electron transfer from g-C3N4 to Co-(Co+Cu)PMOF. Benefiting from its larger capacitance and faster charge transfer rate than g-C3N4 and Co-(Co+Cu)PMOF, g-C3N4@Co-(Co+Cu)PMOF-50% exhibits superior catalytic activity with a high Faradaic efficiency of CO (97.8%) and large current density of -2.1 mA•cm−2 at -1.4 V compared with pristine Co-(Co+Cu)PMOF and other porphyrin-based MOF analogues. The high performance might ascribe that Co centers in porphyrin rings acquire more electrons to activate CO2 which can be converted to intermediate *COOH through evidences from the experimental results and theoretical calculations. This work provides a new insight into the rational design of electrocatalysts for the CO2RR using porphyrin-based conjugated MOFs.