Concentration-Adaptive Electrocatalytic Urea Synthesis From CO₂ and Nitrate via Porphyrin and Metalloporphyrin MOFs

Traditional urea synthesis via the Bosch-Meiser process suffers from high energy consumption and greenhouse gas emissions. Electrocatalytic urea production from carbon dioxide (CO₂) and nitrate (NO₃ ^-) under ambient conditions offers a sustainable alternative, yet challenges persist due to variable NO₃ ^- concentrations and competing side reactions. Herein, we propose porphyrin metal-organic framework (PMOF) and Cu-porphyrin MOF (Cu-PMOF) catalysts for NO₃ ^- concentration-adaptive urea synthesis. Density functional theory (DFT) calculations reveal that PMOF weakly adsorbs *NO₂ via hydrogen bonding, favoring its coupling with *CO₂, while Cu-PMOF strongly binds *NO₂ at Cu sites, facilitating spontaneous *NO/*CO coupling to form *OCNO intermediates under dilute NO₃ ^- conditions. Experimentally, PMOF achieves a urea yield of 28.6 µmol h^-1 mg_cat ^-1 and a Faradaic efficiency (FE) of 23.1% in 0.1 M NO₃ ^-, whereas Cu-PMOF outperforms in 0.05 M NO₃ ^- with a yield of 25.5 µmol h^-1 mg_cat ^-1 and FE of 52.7%. In situ spectroscopy and mechanistic study confirm distinct pathways: PMOF relies on stepwise coupling of *HNO₂ with *CO₂, while Cu-PMOF enables consecutive *NO-*CO coupling. This work highlights adaptive electrocatalyst design for efficient C-N coupling, advancing sustainable urea synthesis.