Biomimetic Construction of Ferriporphyrin-Based Porous Catalysts for Boosting Nitrogen Electroxidation to Nitrate

Electrocatalytic N₂ oxidation reaction (NOR) is an environmentally sustainable approach to synthesize NO₃⁻ under mild conditions. Inspired by the ferriporphyrin (FePP) catalytic species in nitrite oxidoreductase, three FePP-based biomimetic catalysts with different functional groups (─NH₂, ─H, and ─COOCH₃) are designed and prepared successfully. Theoretical calculations indicate that these functional groups can alter the electron density of Fe catalytic center, affecting their ability to adsorb and activate N₂. The strong electron-donating ability of ─NH₂ group can enhance the electron density of iron sites, which reveals a maximum NO₃⁻ yield of 728.55 µmol h⁻¹ g_FePP⁻¹ and a high Faradaic efficiency of 10.6%. After that, the optimized FePP molecules can be encapsulated into ZIF-8, which remarkably promoted the N₂─to─NO₃⁻ transformation with a NO₃⁻ production rate of 1767.74 µmol h⁻¹ g_FePP⁻¹, achieving the highest catalytic effect among metalloporphyrin-based molecular catalysts under mild conditions. This work develops an available biomimetic approach to modulate the electron distribution of active metal sites and confine catalytic species into porous crystalline materials for constructing high-performance NOR electrocatalysts.