The electrocatalytic conversion of nitrate to ammonia has made significant progress as a promising strategy for removing NO₃⁻ and producing NH₃. However, there is a lack of an efficient electrocatalyst to achieve highly selective NH₃ synthesis under low concentration NO₃⁻ conditions. In this study, we design and synthesize a bimetallic copper-containing metal-organic framework (MOF) (CuInL₄, L = 4-(4-pyridyl)benzoic acid), named InCu-MOF, which possesses 2-fold interpenetrating structure and high-density catalytic sites. InCu-MOF is the first MOF catalyst applied to NH₃ synthesis at low NO₃⁻ concentration. Benefiting from the regulation of electronic properties and synergistic catalytic effects of two metal active sites, InCu-MOF exhibits high catalytic activity for the low concentration of NO₃⁻ reduction reaction (NO₃RR) for the first time. At a potential of −1.0 V (vs. RHE), InCu-MOF achieves NH₃ faradaic efficiency (FE) of 82% and yield rate of 892 µg·h⁻¹·mg_cat⁻¹, which FE is 2.6-fold and yield rate are 8.1-fold higher than that of In-MOF. The design and synthesis of this interpenetrating bimetallic MOF provides an idea for the construction of an efficient catalyst at low NO₃⁻ concentrations.