Space-confined charge transfer turns on multicolor emission in metal-organic frameworks via pressure treatment

Single-component multi-emissive materials with stimuli-responsive properties offer unique advantages in the field of multicolor-tunable photoluminescence (PL). However, precisely modulating the emission of each component and achieving high-efficiency emission present a formidable challenge. Herein, we demonstrate that space-confined charge transfer (CT) turns on bright blue-green-white emission in initially faintly emissive metal-organic frameworks (MOFs) at ambient conditions through pressure treatments. Pressure treatments induce a transition from the initial long-range CT to a space-confined mode, significantly amplifying radiative transitions. Furthermore, the space-confined CT, which occurs between mutually perpendicular ligands, significantly influences the spin-orbit charge transfer intersystem crossing. Precise tuning of space-confined CT kinetics via multi-level pressure treatments allows us to modulate the fluorescence-to-phosphorescence ratio, achieving multicolor-tunable emission in the target MOFs. Our work advances the development of multicolor-tunable smart PL materials and unlocks the potential for their application in atmospheric environments.