Conductive metal-covalent organic frameworks as novel catalytic platforms for reduction of nitrate to ammonia

Abstract

With their abundant metal sites, ordered porous structure and great conductivity, conductive metal–organic frameworks display many excellent single-atom electrocatalytic activities, superior to those of conventional inorganic nanostructures. However, their electrochemical application is greatly limited by the fragility of coordinated frameworks. Here, we describe a metal-covalent organic framework (MCOF) strategy to construct a nitrate reduction (NRA) catalyst using M₃·HATN as the subgroup. Assisted by a salt-template, M-HATN-COFs with abundant metal sites (M at% ≈ 12.5%) are achieved by a one-step coordination–condensation approach. More importantly, the M-HATN-COFs provide reasonable platforms for studying the metal-atom catalytic mechanism, surpassing that of current inorganic structures. The Mo-HATN-COFs exhibit outstanding electrocatalytic properties with a high ammonia yield rate (8.52 mg h⁻¹ cm⁻²), FE (91.3%) and stability for the NRA reaction. As the first work on MCOFs for electrochemical NRA reactions, the M-HATN-COF strategy will innovate the design concept of next-generation catalysts and the catalytic mechanism of single-metal atoms.