Spectroscopic Investigation of Defect-Enabled Long-Lived Emission in Photoactive Metal-Organic Frameworks

Novel insights into the photophysical properties of photoactive Metal-Organic Frameworks (MOFs) can be unveiled by applying highly sensitive materials characterization techniques such as time-resolved photoluminescence (TRPL) spectroscopy. TRPL enables the detection of weak, long-lived photon emission in MOFs out to 1 μs, substantially longer than previously reported. The long-lived emission reveals unexpected electronic state population dynamics by tracking the change in emission wavelength and intensity over time. The long-lived emission can be attributed to defect-enabled delayed charge recombination. TRPL can be applied to a range of systems displaying long-lived emission including a tetraphenylethylene based MOF, CORN-MOF-1, & MOF-74. The extent of long-lived, defect-enabled emission can be tuned by engineering the defect density of the material or adjusting the local packings of photoactive linkers in the MOFs. Defect-engineering allows for a tunable and enhanced photophysical response of a range of MOF systems. Tuning these properties aids in tailoring novel materials for improved photoactive devices such light emitting devices or photovoltaics. Precise control and understanding of light-matter interaction is critical for the development of the next generation of light-based devices.