Cu₃TiO₄/Carbon Dots/g-C₃N₄ Heterojunction: An Efficient Photocatalyst for Multifarious Reactions

The demand for multifunctional photocatalysts in organic transformations has been steadily increasing owing to several key factors, such as energy efficiency, selective activation, versatility, and sustainable chemistry. Photoredox catalysis, which is driven by visible light, has recently emerged as a novel activation approach with the potential to serve as an environmentally friendly replacement for the present thermal catalytic systems. In the present study, we report the photocatalytic activity of a multifunctional Cu3TiO4/carbon dots (CDs)/g-C3N4 heterojunction to trigger a sequence of organic transformations, including C(sp2)–O and C(sp3)–O bond formation, and the Click reaction under blue LED exposure with excellent TON and TOF. The CDs present in the heterojunction are excellent electron mediators that drive the reaction pathway to follow photoredox catalysis. The structural, optical, interfacial, morphological properties, functional group analysis, and elemental composition of the prepared nanomaterials were analyzed using XRD, UV–vis DRS, steady-state fluorescence, BET, HRTEM, XPS, EIS, and time-resolved photoluminescence. Notably, lifetime studies show an increased exciton lifetime of 16.31 ns for the prepared nanocomposite. XPS analysis confirmed the +1 and +2 oxidation states of Cu in the nanocomposite. From Mott–Schottky analysis, the conduction band values of g-C3N4 and Cu3TiO4 were calculated to be −1.05 and −1.73 V. Thereby, a highly efficient Z-scheme-plausible heterojunction is constructed. Additionally, scavenging studies help to identify the generation of electrons and holes during photocatalysis. Atomic absorption spectroscopy was used to identify any leaching of Cu ions in the reaction mixture during successive catalytic cycles. The results show that even after five cycles, only 1.9 ppm of Cu ions leached into the reaction mixture.