Research Projects

In this current proposal, we aim to design and synthesize afterglow phosphorescent Metal-organic Frameworks (MOFs) with the building block of pyromellitic diimide (PmDIs) units by means of dynamic imidation or covalent chemistry further through guest inclusion tunability inside the MOFs' pore. "Afterglow” means an intrinsic long-lasting luminescence process, which persistent even after removal of the excitation source. This afterglow luminescent materials have drawn significant attention towards the application in various fields like, optical storage and sensors1, organic light emitting diodes2,3, information technology4, biological imaging5, security system6 and so on. Luminescent MOFs, recently are being extensively studied and explored as promising candidates as new afterglow phosphor materials. The first report on the afterglow MOFs comes in 2016 by Yan and coworkers.7 The afterglow luminescence in MOFs arises with a variety of mechanisms and interactions within the MOF structure, owing to its rigid and periodic frameworks, strong coordination interactions between organic ligands and metal centers and host-guest charge transfer (CT) mechanisms which are attributed to facilitate the intersystem crossing (IsC) from singlet to triplet excited states and to inhibit the non-radiative relaxation of triplet excitons. Though, it is a challenging task to attain proficient long lived room temperature phosphorescent (RTP) MOFs with high quantum yield and are yet to be realized. However, the judicial selection of organic struts with tunable functionalities can pave the way of rational designing of room temperature phosphorescent MOFs to achieve a long-lived afterglow. The facile and tunable guest inclusion phenomenon in an otherwise non-emissive MOFs can effectively introduce a CT interaction between a π-electron deficient host and π-electron rich guest and to attain phosphorescent MOFs by increasing the population in the triplet state, even at room temperature. The core-substituted pyromellitic diimide derivatives have been extensively explored as an efficient triplet harvesting molecular platform by George and co-workers.8-11 However, designing of ambient phosphorescent MOFs with core-substituted PmDI derivatives has not been explored so far. Thus, herein the focus of our project will be utilizing the core substituted PmDI derivatives towards rational designing and synthesis of room temperature phosphorescent MOFs with long-lived afterglow.