Constructing Well-Defined and Robust Th-MOF-Supported Single-Site Copper for Production and Storage of Ammonia from Electroreduction of Nitrate

A combined technique of production and storage of ammonia (NH₃) from electroreduction of nitrate (NO₃ ⁻) through one material is highly desirable but remains a huge challenge. Herein, we proposed a proof-of-concept strategy for combined NH₃ production and storage from electroreduction of NO₃ ⁻ through elaborately designing a single-site CuII-bipyridine-based thorium metal-organic framework (Cu@Th-BPYDC). Noticeably, the single CuII site, anchored by a solid-liquid postsynthetic metalation within Th-BPYDC, shows a novel square coordination structure, as determined by the single-crystal X-ray diffraction. This strongly implies its enormous potential as an open metal site and consequently enables excellent performance in electroreduction of NO₃ ⁻ for NH₃ production, giving 92.5% Faradaic efficiency and 225.3 μmol h⁻¹ cm⁻² yield. Impressively, we can further use Cu@Th-BPYDC material to effectively capture the previously produced NH₃ from electroreduction of NO₃ ⁻, affording an uptake up to 20.55 mmol g⁻¹ at 298 K at 1 bar. The results in this work will outline a new direction toward the combined technique for advanced electrocatalysis such as gas production plus storage/or separation.