Molecular Engineering of a Metal‐Organic Polymer for Enhanced Electrochemical Nitrate‐to‐Ammonia Conversion and Zinc Nitrate Batteries

Abstract

Metal-organic framework-based materials are promising single-site catalysts for electrocatalytic nitrate (NO₃ ^- ) reduction to value-added ammonia (NH₃ ) on account of well-defined structures and functional tunability but still lack a molecular-level understanding for designing the high-efficient catalysts. Here, we proposed a molecular engineering strategy to enhance electrochemical NO₃ ^- -to-NH₃ conversion by introducing the carbonyl groups into 1,2,4,5-tetraaminobenzene (BTA) based metal-organic polymer to precisely modulate the electronic state of metal centers. Due to the electron-withdrawing properties of the carbonyl group, metal centers can be converted to an electron-deficient state, fascinating the NO₃ ^- adsorption and promoting continuous hydrogenation reactions to produce NH₃ . Compared to CuBTA with a low NO₃ ^- -to-NH₃ conversion efficiency of 85.1 %, quinone group functionalization endows the resulting copper tetraminobenzoquinone (CuTABQ) distinguished performance with a much higher NH₃ FE of 97.7 %. This molecular engineering strategy is also universal, as verified by the improved NO₃ ^- -to-NH₃ conversion performance on different metal centers, including Co and Ni. Furthermore, the assembled rechargeable Zn-NO₃ ^- battery based on CuTABQ cathode can deliver a high power density of 12.3 mW cm^-2 . This work provides advanced insights into the rational design of metal complex catalysts through the molecular-level regulation for NO₃ ^- electroreduction to value-added NH₃ .