Supramolecular organic framework nanosheets for efficient singlet oxygen generation: a multilevel energy transfer approach for photocatalytic Minisci reactions

Abstract

Replicating the multistep and sequential energy transfer observed in natural photosynthesis, the development of artificial light-harvesting systems (LHSs) capable of sequential multistep energy transfer remains a challenging and active area of research. In the present work, we have designed and synthesized a triphenylamine-modified cyanophenylenevinylene derivative (TPCI), which can self-assemble with cucurbit[8]uril (CB[8]) via host–guest interactions to form a supramolecular organic framework (SOF). The structural restrictions of its macrocyclic framework greatly enhance the fluorescence emission intensity of the SOF compared to the monomeric TPCI molecule, rendering it an optimal energy donor and pertinent for the advancement of light-harvesting systems (LHSs). Utilizing the SOF as the energy donor, we identified two distinct cyanine dyes (Cy5 and IR) and successfully developed a sequential light-harvesting system (LHS) from SOF to Cy5, followed by IR with high energy transfer efficiency. Through stepwise energy transfer, the singlet oxygen (¹O₂) generation efficiency is progressively enhanced, which exhibited remarkable catalytic efficiency in the Minisci-type alkylation reaction. This study provides a thorough investigation into the development of sequential energy transfer in SOFs as type II photosensitizers for photocatalytic organic transformations.