Ammonia has been obtained from the Haber–Bosch process for decades, which requires an unendurably high temperature and high pressure. Alternatively, electrochemical conversion of N2 to NH3 turns out to be a promising method with much lower energy consumption and accessible reaction conditions. In this work, a novel nano-gold catalyst supported on a boron organic polymer (Au/M-BOP) was prepared and achieved both excellent ammonia yield and faradaic efficiency at low potential (r(NH3): 45.54 μg h−1 cm−2 or 75.89 μg h−1 mgcat.−1 FE: 10.35%), results that are close to the top of the pyramid compared to published literature results. Moreover, the catalyst is conveniently accessible through a pre-immobilized in situ reduction, and can maintain its electrocatalytic activity for multiple uses, which could have potential implications in the industrialization of the electrocatalytic production of ammonia.