CO₂-enhanced TADF of an ultra-stable Cu(i) cluster via guest-host π-π interaction

Efficient and reversible luminescence detection for CO₂ without solvent assistance is of great significance but remains challenging to achieve, due to the lack of efficient interaction between CO₂ molecules and the host emitting center. Benefiting from the abundant host-guest interactions, metal clusters provide a platform for detecting small molecules. However, the insufficient chemical stability of most metal clusters limits their practical applications. Here, we report a hydrophobic Cu(i) cluster (denoted as CuIDPO) with one-dimensional channels. Notably, it displays exceptional chemical stability in both acidic and alkaline aqueous solutions (pH = 1-14). More importantly, CuIDPO shows remarkable CO₂-induced luminescence enhancement (up to 385% under 1 bar CO₂), which can be applied to analyze CO₂ content (LOD = 7.7 mbar). Crystallographic analysis and theoretical calculations suggest the mechanism of CO₂-locking rotation of the phenyl groups in the Cu(i) cluster through guest-host π-π interaction, which is quite unique when compared to the known acid-base neutralization and framework flexibility adjustment mechanisms. Such luminescence CO₂ sensing shows advantages like ultrafast response and good reversibility. Additionally, CuIDPO-loaded membranes were fabricated for spatially resolved 2D visual detection.