Resorcinol–Azodianiline Covalent Organic Framework Supported FeOOH Quantum Dot-Catalyzed Electrochemical Ammonia Synthesis under Ambient Conditions

Abstract

Covalent organic frameworks (COFs) represent bulk crystalline organic polymers characterized by their significant surface area and well-organized pores. By carefully selecting building blocks, we can tailor COF structures with strategically placed heteroatoms. This deliberate inclusion enhances their stability, surface area, and guest-binding ability, which make them highly versatile catalyst supports. Importantly, heteroatoms within COF pores under an applied potential can amplify the catalyst’s desired properties. FeOOH, when grown as nanosized QDs, can exhibit semiconducting band gaps, and their amorphous form can be rich in defects, making them catalytically active. Here, we synthesized a heterogeneous electrocatalyst (FeOOH@COF) consisting of FeOOH supported on an imine-linked covalent organic framework (IISERP-COF33) under mild conditions. Electron microscopy, ICP, and XPS validate the homogeneous distribution (13.2 wt %) of nanosized FeOOH quantum dots (QDs) within the COF (average particle size distribution: 2.7 nm). Thus, the Lewis–Bronsted acidity-rich FeOOH accommodated at keto and nitrogen-rich anchoring sites within the COF pores defines the active and recyclable electrocatalyst. This composite system catalyzes ambient condition ammonia production from nitrogen with a yield of 77.4 μg h–1 mgcat–1 and faradaic efficiency of 46.4% at −0.4 V in 0.1 M LiClO4 aqueous solution, surpassing other COF and iron-based electrocatalysts reported thus far. This work elucidates an accessible aqueous-stable COF-QD electrocatalyst for energy-efficient ammonia production.