Halide perovskites (PVKs) are an exciting family of semiconductors that have seen tremendous growth in research interest due to their excellent optoelectronic properties including, high photoluminescence quantum yield (PLQY), bandgap and dimensional tunability on demand, defect tolerance and low-cost synthesis. These excellent photophysical properties have led to significant successes in both solar cells and light-emitting diodes (LEDs), with record efficiencies reaching more than 25% and 20% for solar cells and LEDs, respectively. However, problems with their inherent atmospheric stabilities remain, limiting their definitive applications.

Recently, the development of PVKs@MOF composites has been shown to improve their stability within atmospheric conditions. Furthermore, the synthesis of PVKs nanocrystals in MOFs as precursors source and sacrificial porous scaffold has resulted in a novel solution-process methodology for producing highly efficient and stable PVK@MOF composites via ion exchange. However, questions remain regarding how PVKs nanocrystals structurally grow and interact within MOFs. In this work, we use synchrotron radiation to perform in-situ SAXS and WAXS analysis of perovskite nanocrystal growth within MOFs, whilst using MOFs as a solid-state nanoreactor. We use this data in conjunction with XRD and structural and photophysical properties to understand the mechanisms that govern the growth of PVKs within MOFs and the physical interactions of the materials, together with their impact on the ensemble bulk properties. These insights will allow us to optimise PVKs growth within MOF frameworks resulting in improved optoelectronic performance and environmental and mechanical stability, as well as develop further novel perovskite synthesis routes from MOF precursors.