Intrinsic Activity of Metalized Porphyrin-based Covalent Organic Frameworks for Electrocatalytic Nitrate Reduction

Electrocatalytic nitrate reduction (NO3RR) to ammonia is a promising alternative to the traditional Haber-Bosch process for the removal of widespread nitrate pollutants. Understanding the structure-activity correlations of the NO3RR) is essential for developing efficient catalysts. Herein, metalized porphyrin-based covalent organic frameworks (COFs) containing optional metal centers and linking units are used to reveal the reaction pathway and intrinsic structure-performance relationship of the NO3RR. The experimental results show that Fe porphyrin-based COFs have the highest activity and ammonia selectivity (FENH3 = 85.4%, NH3 yield rate = 1883.6 mu mol h-1 mg-1COF) among COFs with different investigated metal centers. Moreover, the higher electron density at the Fe center as regulated by the linking units significantly decreased the selective reduction ability from nitNO3- to NH3 of the COFs. Theoretical calculations confirmed that the reaction pathway and *NO to *NHO are potential-dependent steps. More importantly, the adsorbed energy of NO on the metal centers (G*NO) is proposed as a highly matched thermodynamic descriptor for evaluating catalytic performance and may be extended to more NO3RR catalysts with well-defined structures. This work illustrates the intrinsic structure-activity relationship of metalized COFs for the NO3RR, which may provide useful guidance for designing efficient electrocatalysts. Metalized porphyrin-based covalent organic frameworks (COFs) containing optional metal centers and linking units are used to reveal their reaction pathway and intrinsic structure-performance relationship toward nitrate reduction reaction (NO3RR). The adsorbed energy of NO on the metal centers is proposed as a matched thermodynamic descriptor for evaluating catalytic performance and can be extended to more NO3RR catalysts with well-defined structures.image