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.