A controllable surface etching strategy for MOF-derived porous ZnCo₂O₄@ZnO/Co₃O₄ oxides and their sensing properties

Here, we report a surface etching strategy for the controllable synthesis of metal-organic framework (MOF)-derived ZnCo₂O₄@ZnO/Co₃O₄ oxides. Different from previous studies, ZnCo-glycolate (ZnCo-gly) spheres acted as sacrificial templates to provide Zn²⁺ and Co²⁺ ions, which coordinated with 2-MeIm to form Zeolitic Imidazolate Frameworks (ZIFs) on the surface of ZnCo-gly. A series of characterizations were employed to clarify the evolution of the surface etching strategy. Interestingly, the ZIF thickness of the ZnCo-gly surface could be controlled by adjusting the reaction time. After calcination, p-n heterojunctions were formed between the MOF-derived ZnO and Co₃O₄, which made it show excellent selectivity to methanal gas.