Ordered macro/micro-porous metal-organic framework of type ZIF-8 in a steel fiber as a sorbent for solid-phase microextraction of BTEX
An ordered array of macropores on microporous metal-organic framework crystals was developed. This array facilitates analyte diffusion in microextraction applications. A prototypical zeolitic imidazolate framework (ZIF-8) was synthesized in the interstitial voids of a polystyrene bead packing of sub-μm polystyrene beads. After removal of polystyrene by dimethylformamide, a single-crystal ordered macroporous ZIF-8 material (SOM-ZIF-8) was obtained. The resulting μm-sized SOM-ZIF-8 crystals are based on a fully-microporous structure containing a macroporous network. The SOM-ZIF-8 crystals were placed in a stainless-steel fiber and applied as a sorbent for the extraction of benzene, toluene, ethylbenzene, and xylenes (BTEX) by headspace solid-phase microextraction (HS-SPME). The fiber was applied to the HS-SPME of BTEX from wastewater samples followed by GC with flame ionization detection. A Plackett-Burman design and Box-Behnken design were carried out to evaluate the variables affecting the method. Figures of merit include (a) limits of detection of 1.0–12 ng·L−1, (b) linear ranges of 0.004–50 μg·L−1, (c) relative standard deviations of 4.6–6.7%, and (d) excellent fiber-to-fiber reproducibility (5.6–6.7% for n = 3). Spiking recoveries between 92 and 106% were obtained for BTEX analysis in wastewater samples. The introduction of an ordered macroporous network on microporous ZIF-8 crystals enhanced analyte uptake. This increases the extraction performance by a factor of 2.5–3.1 when compared to analogous ZIF-8 crystals that lack templated macropores.
KeywordsZeolitic imidazolate frameworks Hierarchically porous materials Ordered macroporous network Polystyrene template Benzene, toluene, ethylbenzene, xylene Gas chromatography
The financial support of this project by University of Mazandaran is gratefully acknowledged.
Compliance with ethical standards
The author(s) declare that they have no competing interests.
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