Two‐Dimensional Metal–Organic Framework Nanosheets with Cobalt‐Porphyrins for High‐Performance CO₂ Electroreduction

Abstract

Abstract The electrochemical reduction of CO 2 presents a promising strategy to mitigate the greenhouse effect and reduce excess carbon dioxide emission to realize a carbon‐neutral energy cycle, but it suffers from the lack of high‐performance electrocatalysts. In this work, catalytic active cobalt porphyrin [TCPP(Co)=(5,10,15,20)‐tetrakis(4‐carboxyphenyl)porphyrin‐Co II ] was precisely anchored onto water‐stable 2D metal–organic framework (MOF) nanosheets (Zr‐BTB) to obtain ultrathin 2D MOF nanosheets [TCPP(Co)/Zr‐BTB] with accessible catalytic sites for the CO 2 reduction reaction. Compared with molecular cobalt porphyrin, the TCPP(Co)/Zr‐BTB exhibits an ultrahigh turnover frequency (TOF=4768 h −1 at −0.919 V vs. reversible hydrogen electrode, RHE) owing to high active‐site utilization. In addition, three post‐modified 2D MOF nanosheets [TCPP(Co)/Zr‐BTB‐PABA, TCPP(Co)/Zr‐BTB‐PSBA, TCPP(Co)/Zr‐BTB‐PSABA] were obtained, with the modifiers of p ‐(aminomethyl)benzoic acid (PABA), p ‐sulfobenzoic acid potassium (PSBA), and p ‐sulfamidobenzoic acid (PSABA), to change the micro‐environments around TCPP(Co) through the tuning of steric effects. Among them, the TCPP(Co)/Zr‐BTB‐PSABA exhibited the best performance with a faradaic efficiency (FE CO ) of 85.1 %, TOF of 5315 h −1 , and j total of 6 mA cm −2 at −0.769 V (vs. RHE). In addition, the long‐term durability of the electrocatalysts is evaluated and the role of pH buffer is revealed.