Engineering Zeolitic-Imidazolate Framework (ZIF) Thin Film Devices for Selective Detection of Volatile Organic Compounds

Thin films of sodalite-type zeolitic-imidazolate frameworks (ZIFs, ZIF-7, 8, 9, 67, 90, and ZIF-65-Zn) with different metal centers and functional moieties are fabricated on SiO2 coated quartz crystal microbalance (QCM) substrates using automatic program controlled repeated direct growth method. The repeated direct growth procedure manipulated here shows great applicability for rapid growth of uniform ZIF thin films with controllable thickness. The fabricated ZIF/QCM devices are used to detect vapor phase volatile organic compounds including alcohol/water, BTEX compounds (benzene, toluene, ethylbenzene and xylene isomers), and hexane isomers. The ZIF/QCM devices exhibit selective detection behavior upon exposure to these chemical vapors. The effects of ZIF pore size, limited pore diameter, surface functionality, and structural flexibility on the sensing performances of ZIF/QCM devices are systematically investigated, which would be beneficial for the practical application of ZIF sensors based on array-sensing technology. Furthermore, the selective adsorption behavior suggests that these ZIF materials have great potentials in the applications of biofuel recovery and the separation of benzene/cyclohexane, xylene, and hexane isomers.