Stable and wide-wavelength tunable luminescence of CsPbX3 nanocrystals encapsulated in metal–organic frameworks

Lead-halide perovskite nanocrystals (PeNCs) possess attractive linear and nonlinear optical properties. However, further adjusting their linear and nonlinear optical properties in a facile way remains a great challenge due to the inevitable instabilities. Herein, an effective host–guest system was successfully constructed by encapsulating PeNCs (CsPbX3 NCs) into a metal–organic framework (MOF), ZJU-28, via a sequential deposition method at ambient conditions. The accessible and charged frameworks of ZJU-28 facilitate the confinement growth of CsPbX3 NCs in the channels under a mild environment, and therefore facile halide-composition adjustment can be achieved by simply tuning the halide stoichiometry of CsX in a solution process, enabling wide-wavelength tunable one- and two-photon excited (1PE and 2PE) luminescence from 450 nm to 660 nm. Moreover, besides the confinement effect, effective separation, passivation and protection of CsPbX3 NCs are still achieved in ZJU-28⊃CsPbX3 crystals, resulting in a giant two-photon action cross-section which is comparable to that of colloidal CsPbX3 NCs densely capped by surface ligands, and significantly enhanced 1PE and 2PE photostability especially for the spectral stability of mixed-halide composites. These results will pave the way for the exploitation of highly stable and emission-tunable PeNCs composites in optoelectronic applications and even future integrated photonics.