Simultaneous Capture and Luminescent Detection of Trace Benzene in Cyclohexane Enabled by π-Accepting Benzothiadiazole Units in a Metal-Organic Framework.

The separation and detection of trace benzene in cyclohexane is a challenging task in the chemical industry due to its nearly identical physical properties. Herein, we report a tailored metal-organic framework (MOF), NIIC-66, which simultaneously addresses both challenges through a synergistic combination of molecular sieving and luminescent sensing. NIIC-66 exhibits exceptional selectivity for benzene over cyclohexane in the liquid phase, with record-high selectivity factors of 998 and 1929 for 10:100 and 1:100 benzene-cyclohexane mixtures, respectively. Practical application demonstrates the purging of benzene from 99.9% cyclohexane to achieve 99.999% purity. Furthermore, benzene adsorption induces a pronounced luminescence response, featuring a significant intensity enhancement and a bathochromic shift. The limit of detection for benzene in cyclohexane is 13 ppm, the lowest value reported to date for liquid-phase detection. Single-crystal X-ray diffraction and computational studies reveal that the exceptional performance arises from the framework's narrow slit-like pores and electron-deficient benzothiadiazole units, which facilitate strong π-π stacking interactions with benzene molecules, enabling both selective capture and luminescent sensing.