Atom-economical synthesis of ZnO@ZIF-8 core-shell heterostructure by dry gel conversion (DGC) method for enhanced H₂ sensing selectivity

The biggest challenge for metal oxide-based hydrogen gas sensors is to eliminate the interference of other gases. Zeolitic imidazolate frameworks, such as ZIF-8, are ideal filters for large molecules because of their fixed pore size. In this paper, the green and economic synthesis method of dry gel conversion (DGC) was first utilized to convert the surface of ZnO into ZIF-8 with 2-methylimidazole (MeIM) as ligand, and a ZnO@ZIF-8 core-shell structure was successfully constructed. TEM et al. characterizations indicated that the thickness of ZIF-8 shell was effectively controlled by the initial MeIM/ZnO molar ratio. The synthesized ZnO@ZIF-8 showed an excellent selective response for H-2 (2.4 to 100 ppm and 0.9 to 50 ppm) over toluene (2.6 to 10 ppm and 0.3 to 1 ppm) at an optimal heating voltage of 5 V as the initial MeIM/ZnO ratio was 0.2, which confirmed that ZnO@ZIF-8 prepared by DGC method showed excellent promise for a practical application as a selective H-2 detector.