CuO@Ag/NH2-MIL-88B(Fe) Heterojunction Photocatalyst for the Photothermal Codriven Synthesis of Benzimidazoles and Biaryls

A photocatalytic heterojunction system was designed by hybridizing silver-deposited CuO nanoparticles (NPs) with an iron-based metal–organic framework (MOF), NH₂-MIL-88B. The resulting system, CuO@Ag/NH₂-MIL-88B, was thoroughly characterized, and its photoactivity was evaluated by using diffuse reflectance and photoluminescence spectroscopies. The combination of NPs and the MOF led to a red shift of the photoabsorption edges of the MOF toward the visible region. The hybrid system exhibited an energy band gap of ∼1.86 eV, in contrast to the pristine MOF with a band gap of ∼2.05 eV. The creation of a heterojunction system, known as the Z-scheme, improved charge transport and minimized charge recombination. Furthermore, the CuO@Ag/NH₂-MIL-88B system demonstrated synergistic photoactivity in the photothermal catalytic synthesis of benzimidazoles and biaryls under visible light irradiation (LED, 100 W), aided by surface plasmonic resonance. The study revealed a high product efficiency ranging from 78 to 95% for benzimidazoles and 70–80% for biaryls, achieved within a short reaction period of 2.5–3.5 h for benzimidazoles and 6–8 h for biaryls, showcasing the photo- and thermal stability of the photocatalyst. Additionally, the photocatalyst exhibited remarkable recyclability and reusability, highlighting its potential for practical applications.