Complex shell Fe-ZnO derived from ZIF-8 as high-quality acetone MEMS sensor

Zeolitic imidazolate frameworks (ZIFs) are a series of materials composited by metal ions and organic ligands with high specific surface area, which might be great precursors to produce metal oxides by calcination for gas sensor application. However, Zn-ZIF (ZIF-8) is hard to transform as ZnO in air and keeping the unique framework simultaneously. In this work, Fe2+ was introduced into the metal node to replace a part of Zn2+ ions, and it could be oxidized as Fe3+ in the calcination to facilitate the oxidation process of the 2-methylimdazole ligands to give Fe-ZnO complex shell with high specific surface area (108 m2/g) and abundant oxygen vacancies (48%). The micro electro mechanical systems (MEMS) sensor based on the 6%-Fe-ZnO complex shell performed outstanding gas sensing properties to the low-concentration acetone vapor, including high response (ΔR/Rg = 11.2 to 5 ppm acetone), superior selectivity (Sacetone/Sethanol = 5.6) and fast response speed (τres = 2.6 s). This work not only provided the research of an exceptional acetone MEMS sensor, but also induced a strategy to produce metal oxide derived from ZIFs with complex structures for the universal synthesis methodology.