Transformation of reactive oxygen species caused by assembly of excitation modules into supramolecular organic frameworks for photocatalysis

The efficient control of singlet oxygen (¹O₂) and superoxide radical ( \({\rm O}_{2}^{\cdot-}\) $${\mathrm{O}}_2^{\cdot -}$$ ) of reactive oxygen species in photocatalytic reactions is synthetically captivating but practically challenging. Herein, we report a new strategy that efficiently realizes the conversion of ¹O₂ to \({\rm O}_{2}^{\cdot-}\) $${\mathrm{O}}_2^{\cdot -}$$ by the assembly of the excitation modules into a host-guest supramolecular organic framework (SOF). A photoactive organic module of a phenyl-bridged bis(triphenylamine) derivative modified by four 4,4′-bipyridin-l-ium (BP) units, named as triphenylamine (TPA)-BP, was pre-synthezied. After the assembly of TPA-BP with curcurbit[8]uril (CB[8]) through the strong complexation of CB[8] with two BP units in a head-to-tail manner, a TPA-BP-SOF was sucessfully constructed, which is a two-dimensional nanosheet structure with a periodic pore structure and homogeneous solubility. It is noteworthy that the formation of TPA-BP-SOF through host-guest interactions might facilitate efficient electron transfer, leading to the production of \({\rm O}_{2}^{\cdot-}\) $${\mathrm{O}}_2^{\cdot -}$$ . In contrast, its monomer TPA-BP dominantly generates ¹O₂ in the photocatalytic process. This study presents a novel approach to effectively convert the type II photosensitizer to the type I photosensitizer by implementing TPA-BP-SOF. Moreover, the \({\rm O}_{2}^{\cdot-}\) $${\mathrm{O}}_2^{\cdot -}$$ species produced by TPA-BP-SOF under light irradiation can effectively catalyze the oxidative hydroxylation of arylboronic acids and the aerobic oxidation of N-phenyltetrahydroisoquinoline in water with the yields of up to 88% and 83%, respectively.