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 mgcat -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 mgcat -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.