<p>Discharge of wastewater containing nitrate (NO₃⁻) disrupts aquatic ecosystems even at low concentrations. However, selective and rapid reduction of NO₃⁻ at low concentration to dinitrogen (N₂) is technically challenging. Here, we present an electrified membrane (EM) loaded with Sn pair-atom catalysts for highly efficient NO₃⁻ reduction to N₂ in a single-pass electrofiltration. The pair-atom design facilitates coupling of adsorbed N intermediates on adjacent Sn atoms to enhance N₂ selectivity, which is challenging with conventional fully-isolated single-atom catalyst design. The EM ensures sufficient exposure of the catalysts and intensifies the catalyst interaction with NO₃⁻ through mass transfer enhancement to provide more N intermediates for N₂ coupling. We further develop a reduced titanium dioxide EM as the anode to generate free chlorines for fully oxidizing the residual ammonia (&lt;1 mg-N L⁻¹) to N₂. The sequential cathode-to-anode electrofiltration realizes near-complete removal of 10 mg-N L⁻¹ NO₃⁻ and ~100% N₂ selectivity with a water resident time on the order of seconds. Our findings advance the single-atom catalyst design for NO₃⁻ reduction and provide a practical solution for NO₃⁻ contamination at low concentrations.</p>