Tailoring benzene based covalent organic frameworks for enhanced nitrogen reduction reaction catalysis

Abstract

Ammonia (NH₃) is regarded as a green energy carrier owing to its low-carbon footprint, pollution-free and environmentally friendly characteristics. Its high hydrogen content (17.6 wt%) and ease of liquefaction at ambient conditions make it as a promising medium for hydrogen storage and long-distance energy transport.¹ Currently, ammonia synthesis relies almost exclusively on the Haber–Bosch process, which operates under high temperature and pressure, consuming substantial energy derived from fossil fuels and contributing significantly to global CO₂ emissions. The electrochemical nitrogen reduction reaction (NRR) offers a sustainable alternative, enabling ammonia production under ambient conditions powered by renewable energy sources. However, NRR is hindered by poor N₂ adsorption and activation, and the competing hydrogen evolution reaction (HER).² In NRR, the catalyst material plays an important role by activating the N₂ molecule, lowering the energy barriers of the reaction pathway and suppressing competing hydrogen evolution. Various types of catalyst materials, metal surfaces, graphene derivatives and porous organic materials have been studied for NRR. However, these materials suffer from drawbacks, such as high cost, limited active-sites, poor selectivity due to competing HER and stability issues under operating conditions. Recently, covalent organic frameworks (COFs) have gained attention due to their high specific surface area, tunable pore structure and tailorable active sites.³ Therefore, in this work, we have explored the impact of transition metals (TM- Cr,Mn,Fe) doping and substitution of functional groups on the catalytic performance of benzene based COFs by using density functional theory calculations. This study provides atomistic insights and design principles for tailoring the COFs toward efficient catalysts for NRR.

Reference

(1)Int.J.HydrogenEnergy 2012,37(2),1482. https://doi.org/10.1016/j.ijhydene.2011.10.004.

(2)ACS Catal.2017,7(1),706. https://doi.org/10.1021/acscatal.6b03035.

(3)ChemCatChem2023,15(11). https://doi.org/10.1002/cctc.202300243.