Nanoparticle-templated hierarchically porous polymer/zeolitic imidazolate framework as a solid-phase microextraction coatings

Abstract

A two-step ZnO nanoparticle-directed method has been implemented to prepare polymer mono-lith/zeolitic imidazolate framework (ZIF) solid-phase microextraction (SPME) fiber coatings with hierarchical micro-meso-macroporosity. The polymer/ZIF monolith was prepared on the surface of a stainless steel wire from a polymerization mixture containing dispersed ZnO nanoparticles. The embedded ZnO nanoparticles in the precursor polymer monolith coating were converted on-fiber to submicrometric porous crystals of the prototypical ZIF-8, based on the coordination of Zn(II) with 2-methylimidazole. The polymer/ZIF monolith coating was applied to the headspace SPME of benzene, toluene, ethylbenzene, and xylenes (BTEX) from water samples, followed by gas chromatography-flame ionization detection (GC-FID). Hierarchically porous polymer/ZIF monolithic coatings showed a superior performance for BTEX extraction in comparison to coatings based on pure macroporous organic polymer monoliths, silicone glue/ZIF-8 coatings or commercial PDMS coatings. Experimental parameters such as desorption temper-ature, desorption time, salt concentration, temperature effect, equilibrium time and extraction time were investigated. Under the selected experimental conditions, limits of detection of 0.02–0.11 g L −1 , linear ranges of 0.2–200 g L −1 , relative standard deviations of 4.3–8.2%, and a fiber-to-fiber reproducibility of 8.9–9.8% (n = 3) were obtained. Recoveries higher than 88% were obtained for BTEX analysis in tap water, wastewater and landfill leachates.