Defect Engineering Strategy for Superior Integration of Metal–Organic Framework and Halide Perovskite as a Fluorescence Sensing Material

Combining halide perovskite quantum dots (QDs) and metal-organic frameworks (MOFs) material is challenging when the QDs' size is larger than the MOFs' nanopores. Here, we adopted a simple defect engineering approach to increase the size of zeolitic imidazolate framework 90 (ZIF-90)'s pores size to better load CH3NH3PbBr3 perovskite QDs. This defect structure effect can be easily achieved by adjusting the metal-to-ligand ratio throughout the ZIF-90 synthesis process. The QDs are then grown in the defective structure, resulting in a hybrid ZIF-90-perovskite (ZP) composite. The QDs in ZP composites occupied the gap of 10-18 nm defective ZIF-90 crystal and interestingly isolated the QDs with high stability in aqueous solution. We also investigated the relationship between defect engineering and fluorescence sensing, finding that the aqueous Cu2+ ion concentration was directly correlated to defective ZIF-90 and ZP composites. We also found that the role of the O-Cu coordination bonds and CH3NHCu+ species formation in the materials when they reacted with Cu2+ was responsible for this relationship. Finally, this strategy was successful in developing Cu2+ ion fluorescence sensing in water with better selectivity and sensitivity.