Super-hydrophobic Cs4PbBr6@PDB composites with water-driven photoluminescence enhancement and dehydration recovery

All-inorganic perovskite quantum dots (QDs) are very promising materials for their potential applications in water-related photoluminescence due to their sensitive properties to water. This work initiatively attempts to absorb Cs4PbBr6 QDs into a super-hydrophobic polydivinylbenzene (PDB) porous framework. Under the protection of PDB, the non-luminescent Cs4PbBr6 and luminescent CsPbBr3 transform reversibly by alternate water treatment (excess or small amount) and removal of water. The extraction of CsBr by water and reinsertion of CsBr by evaporation from/into the QDs make up a reversible phase transformation process. The super-hydrophobic porous structure of PDB not only provides the confined space for dissolved CsBr but also inhibits the overflow of trapped CsBr, thereby reducing the adverse impact of excess water on reversible hydrochromism. This work provided a new perspective to understand the phase conversion between Cs4PbBr6 and CsPbBr3. Furthermore, the Cs4PbBr6@PDB in waterborne luminescent inks by screen printing opens a way in the field of anti-counterfeiting owing to the excellent stability of encryption and decryption.