Guest-Regulated Generation of Reactive Oxygen Species from Porphyrin-Based Multicomponent Metallacages for Selective Photocatalysis

The development of novel materials for highly efficient and selective photocatalysis is crucial for their practical applications. Herein, we employ the host-guest chemistry of porphyrin-based metallacages to regulate the generation of reactive oxygen species and further use them for the selective photocatalytic oxidation of benzyl alcohols. Upon irradiation, the sole metallacage (6) can generate singlet oxygen (1O2) effectively via excited energy transfer, while its complex with C70 (6 superset of C70) opens a pathway for electron transfer to promote the formation of superoxide anion (O2 & sdot;-), producing both 1O2 and O2 & sdot;-. The addition of 4,4 '-bipyridine (BPY) to complex 6 superset of C70 forms a more stable complex (6 superset of BPY) via the coordination of the Zn-porphyrin faces of 6 and BPY, which drives fullerenes out of the cavities and restores the ability of 1O2 generation. Therefore, benzyl alcohols are oxidized into benzyl aldehydes upon irradiation in the presence of 6 or 6 superset of BPY, while they are oxidized into benzoic acids when 6 superset of C70 is employed as the photosensitizing agent. This study demonstrates a highly efficient strategy that utilizes the host-guest chemistry of metallacages to regulate the generation of reactive oxygen species for selective photooxidation reactions, which could promote the utilization of metallacages and their related host-guest complexes for photocatalytic applications. A Zn-porphyrin-based metallacage exhibited strong host-guest interactions with fullerene derivatives. The complexes could be dissembled by the further addition of 4,4 '-bipyridine to form a more stable coordinated complex. This tunable host-guest complexation was further employed to generate different types of reactive oxygen species, enabling the highly efficient and selective photocatalytic oxidation of benzyl alcohols.+ image