Unsaturated p-Metal-Based Metal–Organic Frameworks for Selective Nitrogen Reduction under Ambient Conditions

Electrochemical ammonia synthesis that utilizes renewable electricity in the nitrogen reduction reaction (NRR) has recently been remarkably considered. Of particular importance is to develop efficient electrocatalysts at low costs. Herein, highly selective nitrogen capture using porous aluminum-based metal-organic frameworks (MOFs) materials, MIL-100 (Al), is first designed for the electrochemical nitrogen fixation in alkaline media under ambient conditions. Owing to the unique structure, MIL-100 (Al) exhibits remarkable NRR properties (NH₃ yield: 10.6 μg h^-1 cm^-2 mg_cat.^-1 and Faradaic efficiency: 22.6%) at a low overpotential (177 mV). Investigation indicates that the catalyst shows excellent N₂-selective captures due to the unsaturated metal sites binding with N₂. More specifically, as the Al 3p band can strongly interact with N 2p orbitals, Al as a main group metal presents a high and selective affinity to N₂. The utilization of multifunctional MOF catalysts delivers both high N₂ selectivity and abundant catalytic sites, resulting in remarkable efficiency for NH₃ production.