An appealing strategy in the direction of circular chemistry and sustainable nitrogen exploitation is to efficiently convert NOx pollutants into low-toxic products and simultaneously provide crop plants with metabolic nitrogen. This study demonstrates that such a scenario can be realized by a defect- and morphology-coengineered Ni-Fe-layered double hydroxide (NiFe-LDH) comprising ultrathin nanosheets. Rich oxygen vacancies are introduced onto the NiFe-LDH surface, which facilitate charge carrier transfer and enable photocatalytic O₂ activation into superoxide radicals (^•O₂^-) under visible light. ^•O₂^- on NiFe-LDH thermodynamically oxidizes NO into nitrate with selectivity over 92%, thus suppressing dangerous NO₂ emissions. By merit of abundant mesopores on NiFe-LDH ultrathin nanosheets bearing a high surface area (103.08 m²/g), nitrate can be readily stored without compromising the NO oxidation reactivity or selectivity for long-term usage. The nitrate species can be easily washed off the NiFe-LDH surface and then enriched in the liquid form as easy-to-use chemicals.