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

Abstract

AbstractElectrocatalytic 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 µmol 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 nitrate to ammonia 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.