Yiyong Zhao, Pengyue Hao, Shuxin Yuan, Wang Zhang, Jinghui Lyu, Ai-Bao Xia*, Yongwu Peng*

Cite this article: https://doi.org/10.1016/j.cjsc.2026.101099

Publication date:

Keywords: Electrocatalytic nitrate reduction; Trinuclear copper cluster; MCOF/SWCNT heterostructures; Catalytic microenvironment modulation; Zn-nitrate battery

ABSTRACT

Electrocatalytic nitrate reduction (eNRR) offers a sustainable route for ammonia production and nitrate remediation, yet the application of covalent organic framework (COF)-based electrocatalysts is hindered by poor charge transport and limited site accessibility. Herein, we report the in-situ growth of two trinuclear copper cluster-based metal-covalent organic frameworks (MCOFs) on single-walled carbon nanotubes (SWCNTs), yielding conductive heterostructures with tailored catalytic microenvironments. Systematic structural modulation reveals that methyl-induced steric effects critically regulate active-site exposure and substrate diffusion. Notably, methyl-free MCOF-1/SWCNT exhibits enlarged pore apertures and enhanced site accessibility, whereas methyl-substituted MCOF-2/SWCNT shows narrower pores but a higher surface area and denser active sites, these competing effects lead to a modest overall performance difference. In 1 M KOH with 0.15 M KNO3 at -0.8 V versus RHE, MCOF-1/SWCNT achieves a Faradaic efficiency of 94.67% and an ammonia yield of 4.94 mol g-1 h-1. In-situ Raman spectroscopy and density functional theory calculations validate a stepwise hydrogenation pathway and identify the *NHO-to-*NH2OH protonation as the rate-determining step, with a lower barrier for MCOF-1/SWCNT. Furthermore, MCOF-1/SWCNT functions as an efficient cathode in a Zn-nitrate battery, achieving a peak power density of 13.2 mW cm-2 and stable operation over 140 h. This work establishes a molecular-level framework for modulating steric microenvironments in MCOF electrocatalysts and demonstrates the potential of coupling nitrate valorization with energy storage.