Boosting Electrocatalytic Ammonia Synthesis via Main-Group Metal Doping and Ionic Liquid Encapsulation in Copper Metal–Organic Frameworks

The electrochemical nitrogen reduction reaction (EN2RR) provides a sustainable method for synthesizing ammonia at room temperature, but it is hindered by the low ammonia faradic efficiency (FE) and production yield. Herein, we report an effective EN2RR electrocatalyst: the ionic liquid-encapsulated aluminum copper bimetallic metal-organic framework (IL-AlCu-MOF). Comparisons across pristine Cu-MOF, AlCu-MOF, IL-Cu-MOF, and IL-AlCu-MOF reveal that the combination of Al doping and IL encapsulation can simultaneously promote dinitrogen activation and accelerate proton generation via water dissociation in a neutral electrolyte, which synergistically enhances the yield and selectivity of ammonia in EN2RR. The IL-AlCu-MOF achieves an NH3 yield of 124.7 μg·h-1·mgcat-1 with an FENH3 of 20.3% at -0.3 V (vs reversible hydrogen electrode, RHE) in 0.1 M K2SO4. In situ attenuated total reflectance surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) measurements indicate improved water dissociation kinetics over that of IL-AlCu-MOF, and differential electrochemical mass spectrometry (DEMS) captures the EN2RR intermediates. Density functional theory (DFT) calculations show that Al doping modulates the Cu electronic structure for enhanced N2 activation, while IL encapsulation strengthens water adsorption at the MOF surface and thus accelerates water dissociation, both of which contribute to boosting the EN2RR performance.