Molecular Weaving of Mixed‐Addenda Polyoxometalates into MOF Nanochannels as Electron‐Buffering Reservoirs for Enhanced Nitrate‐to‐Ammonia Electrocatalysis
Gang Li, Xinming Wang, Haijun Pang, Huiyuan Ma
Abstract
ABSTRACT Electrochemical conversion of nitrate pollutants into value‐added ammonia (e‐NO 3 RA) offers a sustainable pathway for nitrogen valorization, yet hinges on the development of efficient electrocatalysts. Herein, we systematically synthesize a series of three V/W mixed‐addenda polyoxometalate ([P 2 W VI 17 V V 1 O 62 ] 7− , noted as P 2 W 17 V 1 ) based metal–organic frameworks [X 9 (DPYB) 9 (OX) 6 (H 2 O) 6 ][P 2 W 17 V 1 O 62 ] denoted as XMOF‐V 1 (X = Fe; Co; Zn, DPYB = 1,4‐Di(pyridin‐4‐yl)benzene, OX = oxalic acid). The incorporation of P 2 W 17 V 1 not only reinforced structural ruggedness and stability, but also promotes multi‐electron transfer, substantially promoting e‐NO 3 RA activity. Among them FeMOF‐V 1 delivers exceptional electrocatlytic nitrat‐to‐ammonia performance with an achieves over 95% Faradaic efficiency across a wide voltage range of −0.6 to −1.4 V vs RHE. This superiority stems from synergistic interplay: P 2 W 17 V 1 acts as an electron reservoir enhancing proton‐coupled charge transfer, while the minimal bandgap of FeMOF‐V 1 facilitates directional electron injection. DFT analyses reveal Fe‐specific mechanisms including strong 3 d ‐orbital hybridization with NO 3 – near Fermi Level (Ef), highly positive Fe sites optimizing adsorption, and transfer weakening N–O bonds, as corroborated by in situ FTIR identification of *NO 3 /*NO/*NH 2 intermediates. Together with effectively suppressed HER (ΔG *H > ΔG *NO3 ), these attributes collectively enable highly selective NH 3 synthesis. This study establishes mixed‐addenda POMOFs as a versatile and efficient platform for sustainable nitrate‐to‐ammonia conversion.