Cu-MOF attached with pyrene-cored probes as a highly sensitive indicator for carbon monoxide in coal mine gas: Synthesis and performance

As a toxic component in coal mine gas, CO has both acute and long-term damages to human health. Suitable CO probes satisfying the requirement for long-distance real-time monitoring in confined space are still underdeveloped. In this work, a series of fluorescent probes derived from pyrene were synthesized and coordinated onto [Cu3(BTC)2(H2O)3]n (H3BTC meant 1,3,5-benzenetricarboxylic acid) via a coordination bond with Cu2+. These probes were carefully analyzed, including their single crystal structure, absorption spectra, excitation spectra, and emission spectra. Their emission response towards CO gas was analyzed, with a sensing mechanism of probe release which was triggered by a dynamic wagging between the trans- and cis- configuration of –C = N–N = C– moiety upon photoexcitation. These probes were attached onto a classic MOF (metal-organic framework) [Cu3(BTC)2(H2O)3]n, which was confirmed by SEM, fluorescence microscopy, XRD, N2 adsorption/desorption, and TGA. The resulting composite samples (denoted as Pm@CuBTC) showed emission recovery upon trace amount CO (LOD = 0.005 % vs N2, 50 ppm), with a short response time of 31 s at room temperature. High sensing selectivity over competing species of alkane was observed, with stable signal for 5 days.