Photo‐Induced Construction and Recovery of Cu+ Sites in Metal–Organic Frameworks

Abstract

AbstractThe adjustment of the valence state of metal ions is crucial for various applications because peculiar activity originates from metal ions with specific valence. Cu+ can interact with molecules possessing unsaturated bonds like CO via π‐complexation, while Cu2+ doesn't have such ability. Meanwhile, Cu+ sites are easily oxidized to Cu2+, leading to the loss of activity. Despite great efforts, the development of a facile method to construct and recover Cu+ sites remains a pronounced challenge. Here, for the first time a facile photo‐induced strategy is reported to fabricate Cu+ sites in metal–organic frameworks (MOFs) and recover Cu+ after oxidation. The Cu2+ precursor was loaded on NH2‐MIL‐125, a typical visible‐light responsive Ti‐based MOF. Visible light irradiation triggers the formation of Ti3+ from Ti4+ in framework, which reduces the supported Cu2+ in the absence of any additional reducing agent, thus simplifying the process for Cu+ generation significantly. Due to π‐complexation interaction, the presence of Cu+ results in remarkably enhanced CO capture capacity (1.16 mmol g−1) compared to NH2‐MIL‐125 (0.49 mmol g−1). More importantly, Cu+ can be recovered conveniently via re‐irradiation when it is oxidized to Cu2+, and the oxidation‐recovery process is reversible.