The electrochemical reduction of nitrogen (NRR) at ambient conditions is an appealing alternative to the industrial method for ammonia synthesis that requires high temperature and pressure, but its efficiency is greatly dependent on stable and efficient electrocatalysts. Hence, by means of comprehensive density functional theory (DFT) computations, we investigated the potential of a new class of metal-organic frameworks (MOF)-based catalyst for the NRR, namely, the synthesized pi-conjugated metal bis(dithiolene) nanosheet (MC4S4, M = Fe, Co, Ni, Ru, Rh, Pd, Pt, Os, and Ir). Our results demonstrated that the NRR catalytic activity of MC4S4 is highly dependent on the central metal atom. Due to the low overpotential (0.31 V), the OsC4S4 nanosheet is predicted to exhibit outstanding NRR catalytic activity through the distal mechanism, in which the hydrogenation of the activated N-2 molecule to the N2H* species is identified as the potential-determining step. Our work is the first report of 2D MOF-based electrocatalyst for N(2 )reduction, opening a new avenue for advancing sustainable NH3 synthesis under ambient conditions.