Molecular engineering of 1D conjugated copper anilate coordination polymers for boosting electrocatalytic nitrate reduction to ammonia

Abstract

The electrochemical nitrate reduction reaction (NO₃RR) offers a “two-birds-one-stone” solution by simultaneously addressing water pollution and enabling green ammonia production. However, its multiple reaction pathways and complex intermediates pose a challenge for designing high-efficiency electrocatalysts. The highly modular nature of metal coordination polymers (MCPs), combined with molecular engineering strategies, provides a pathway for systematically exploring the structure–performance relationships of catalysts. As a proof of concept, we here synthesized a series of π–d conjugated copper anilate coordination polymers incorporating different halogen atoms (F, Cl and Br). The combined experimental and theoretical investigations reveal that introducing halogen atoms with electron-withdrawing properties can create an electron-deficient Cu center through the interchain Cu⋯halogen supramolecular interactions, which can effectively lower the energy barrier for deoxygenation of the *NO intermediate. As a result, the Cu–FA (FA = fluoranilate, C₆O₄F₂²⁻) achieves a superior NO₃RR performance with the faradaic efficiency (FE) of 98.17% and yielding rate of 14.308 mg h⁻¹ mg⁻¹ at −0.9 V, nearly 7.7 times that of the pristine Cu–DABQ (DABQ = 2,5-dihydroxy-1,4-benzoquinone, C₆O₄H₂²⁻). This study may provide new insights into the design of high-performance NO₃RR electrocatalysts.