Organic photocatalysts have been widely studied for their potent redox capabilities and for their applicability as next-generation catalytic materials. However, the development of these molecules towards applications in well-established catalytic systems has often been impeded by their low turnover numbers as a result of short excited state lifetimes, low quantum yields and fast photobleaching. In this work, a new strategy to enhance the photocatalytic performance of an organic photocatalyst through the integration into a highly charged porous coordination cage, PCC-5, is addressed. Porous coordination cages (PCCs) are crystalline well-ordered porous coordination compounds constructed through assembling organic ligands and metal ions via coordination bonds. More importantly, the functions and properties of the PCCs are inherited from its ligands: catalytic capabilities, fluorescence, charge, and chemical reactivity. With the host-guest supramolecular interactions between the PCC and the quencher of the photocatalyst, the quenching of the short-lifetime excited state of the photocatalyst is expected to be more effective and more frequent. The molecular confinement provided by incorporation of the catalyst into the cage backbone largely restrains the configuration swing of the catalyst during light radiation, preventing unwanted photobleaching. In this report a new anionic PCC, PCC-5, is presented as a catalyst towards the trifluoromethylation of triphenylethylene using the Umemoto reagent. The selected panel ligand, a triazine-based organic photocatalyst is integrated directly into the octahedral cage. The vertex ligand in the structure provides negative charges and thereby enables electrostatic interactions between the cage and the cationic guest. The results and influencing factors for the dramatic increase in catalytic performance of the cage over that of the free organic catalyst are studied and addressed. Additionally, the long-term usability of this system regarding stability and catalytic turnover number is discussed.

Photocatalytic trifluoromethylation utilizing an organic photocatalyst-based anionic porous coordination cage

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.