Revealing the structure-activity relationship of two Cu-porphyrin-based metal-organic frameworks for the electrochemical CO2-to-HCOOH transformation

The eCO(2)RR activity is correlated to the internal structural character of the catalyst. We employed two types of structural models of porphyrin-based MOFs of PCN-222(Cu) and PCN-224(Cu) into heterogeneous catalysis to illustrate the effect of structural factors on the eCO(2)RR performance. The composite catalyst PCN-222(Cu)/C displays better activity and selectivity (eta = 450 mV, FEHCOOH = 44.3%, j = 3.2 mA cm(-2)) than PCN-224(Cu)/C (eta = 450 mV, FEHCOOH = 34.1%, j = 2.4 mA cm(-2)) for the CO2 reduction to HCOOH in the range of -0.7--0.9 V (vs. RHE) due to its higher BET surface area, CO2 uptake, and a larger pore diameter. It is interesting that PCN-224(Cu)/C displays better performance in the range of -0.4--0.6 V (vs. RHE) due to its greater heat of adsorption, Q(st) and a higher affinity for CO2 molecule, which could promote the capture of CO2 onto the exposed active sites. As a result, PCN-224(Cu)/C exhibits better stability for the long-term electrolysis.