Ficarra G, Sciortino A, Barbata L G, Ettlinger R, De Michele V, Marin E, Cannas M, Morris R E, Buscarino G
Department of Physics and Chemistry "Emilio Segrè", University of Palermo, Via Archirafi 36, 90123 Palermo, Italy.
TUM School of Natural Sciences, Technical University of Munich Lichtenbergstr. 4, 85748 Garching b. München, Germany.
Phys Chem Chem Phys. 2024 Aug 22;26(33):22269-22277. doi: 10.1039/d4cp02279c.
The world of metal-organic frameworks (MOFs) has become a hot topic in recent years due to the extreme variety and tunability of their structures. There is evidence of MOFs that exhibit intrinsic luminescence properties that arise directly from their organic components or from the interaction between them and metallic counterparts. A new perspective is to exploit the porous nature of MOFs by encapsulating luminescent guests, such as organic dyes, in order to explore possible changes in the luminescence activity of the combined systems. This work is focused on the optical study of zirconium-based MOF-808 and its interaction with encapsulated rhodamine B molecules. Using a plethora of different techniques, we were able to unravel its photocycle. MOF-808 displays intrinsic luminescence activity that derives from an energy transfer process from the linker to the metal sites occurring in 300 ps. The emission is a singlet-singlet transition in aqueous solution, and it is a triplet transition in powdered form. After exploring the bare MOF, we combined it with rhodamine B molecules, following an easy post-synthetic process. Rhodamine B molecules were found to be encapsulated in MOF pores and interact with the MOF's matrix through nanosecond energy transfer. We created a totally new dual-emitting system and suggested a way, based on the time-resolved studies, to clearly unravel the photocycle of MOFs from the very first photoexcitation.
近年来，金属有机框架（MOF）领域因其结构的极端多样性和可调节性而成为热门话题。有证据表明，一些MOF表现出内在的发光特性，这些特性直接源于其有机成分或它们与金属对应物之间的相互作用。一个新的观点是通过封装发光客体（如有机染料）来利用MOF的多孔性质，以探索组合系统发光活性的可能变化。这项工作聚焦于基于锆的MOF-808的光学研究及其与封装的罗丹明B分子的相互作用。使用大量不同的技术，我们得以揭示其光循环。MOF-808表现出内在的发光活性，这源于在300皮秒内发生的从连接体到金属位点的能量转移过程。在水溶液中，发射是单重态-单重态跃迁，而在粉末形式下是三重态跃迁。在研究了纯净的MOF之后，我们通过一个简单的后合成过程将其与罗丹明B分子结合。发现罗丹明B分子被封装在MOF孔中，并通过纳秒级的能量转移与MOF的基质相互作用。我们创建了一个全新的双发射系统，并基于时间分辨研究提出了一种方法，以便从首次光激发开始就清晰地揭示MOF的光循环。
