Density Functional Theory Study of Nitrogen Fixation Electrocatalysts Based on Two-Dimensional Conjugated Metal–Organic Frameworks

Creating high-performance single-atom catalysts for the electrochemical nitrogen reduction reaction (NRR) is a crucial approach. Two-dimensional metal–organic frameworks (MOFs) have captured significant attention as NRR catalysts due to their lightweight and large pores. Using density functional theory (DFT) calculations, we explored a series of TM3C18N6X12 (X = S or NH, TM = Mo, Cr, W, Fe, Mn, Os, Ni, Ir, Pd, Pt, Rh) two-dimensional metal–organic frameworks (MOFs) as potential single-atom catalysts for NRR through a three-step screening strategy. The influence of coordinating atoms around transition metal atoms is also examined, specifically, TMS4 or TMS2(NH)2. Our findings indicate that the Os3C18S12N6 MOF exhibits the best activity and selectivity, with an overpotential of only 0.28 V along the distal pathway, which is lower than most reported MOF materials. The adsorption and activation of N2 are influenced by the σ-acceptance-π* donation mechanism. Additionally, we established descriptors related to the valence electron (ΔQTMXTM) and magnetic moment (μTM–μX) to explore the relationship between catalytic activity and descriptors. This work can offer valuable insights for designing promising electrocatalysts for NRR based on MOFs.