Luminescence detection of CH2Cl2 by varying Cu⋯Cu interactions in a flexible porous coordination polymer†

Owing to the weakness of the interaction between chlorohydrocarbon and the host framework, the development of reversible and vapochromic coordination polymer (CP)-based luminescence sensors for the detection of CH₂Cl₂ with a fast response is still challenging. In this study, a flexible Cu(I)-CP, [Cu₂I₂(PPh₃)₂(PYZ)] (CIPP, PPh₃ = triphenylphosphine, PYZ = pyrazine) is reported. The intra-cluster Cu⋯Cu distance in CIPP is quite sensitive to the external stimuli, resulting in the corresponding luminescence color and intensity change. Based on this feature, the fast (11 s), distinguishing (wavelength shift of 45 nm), and reversible luminescence response of CIPP for CH₂Cl₂ is realized. Crystallographic analysis suggests that the presence/removal of CH₂Cl₂ can affect the Cu⋯Cu distance, which is the origin of the responsive luminescence. In addition, the multiple weak interactions between CH₂Cl₂ and the framework afford the strong adsorption of CH₂Cl₂ into CIPP, which can be maintained for at least 5 minutes when exposed to air, thereby ensuring accuracy in the sensing process.