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

The electrochemical reduction of CO2 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‐CoII] 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 CO2 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 (FECO) of 85.1 %, TOF of 5315 h−1, and jtotal 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. Selective and effective CO2 electroreduction: Catalytically active cobalt porphyrin [TCPP(Co)=(5,10,15,20)‐tetrakis(4‐carboxyphenyl)porphyrin‐CoII] 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 CO2 reduction reaction.