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 CHNHPbBr 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 Cu 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 CHNHCu species formation in the materials when they reacted with Cu was responsible for this relationship. Finally, this strategy was successful in developing Cu ion fluorescence sensing in water with better selectivity and sensitivity.