Long excited state lifetime of thermally activated delayed fluorescent photosensitizer integrated into Metal-organic framework enables efficient CO2 photoreduction

Abstract

The performance of metal–organic-framework-based photocatalysts were usually limited by the short lifetime of excited state and the high cost of precious metal complexes in CO2 photoreduction. To enhance the lifetime of excited state, an organic thermally activated delayed fluorescence photosensitizer was installed with the non-noble zinc node in a periodic structure named Spiro-Zn-MOF. The horizontally prolonged linker based on D-A (D: Donor, A: Acceptor) unit provided a delayed lifetime up to micro-second-level lifetime for excited state, which was inherited in the Spiro-Zn-MOF. And the inborn D-A structure of Spiro-Zn-MOF worked with zinc node in a synergistic way, leading to a large photocathode current in the scaffold allowing for high photoreduction rate. Combination of long-lived excited state and efficient charge transfer in noble-metal-free D-A unit allowed for efficient CO2 photoreduction with a production rate of CO up to almost 50 μmol h−1 g−1, which far exceeded the performances of zinc-based MOF-5 and commercialized TiO2 (P25) under the same conditions.