Designing a Photoactive Polyoxometalate-Based Metal–Organic Framework for Solar-Powered Hantzsch Reactions in a Divergent and Mild Pathway to Thermal Methods

Developing a photocatalytic strategy for the multicomponent Hantzsch reaction to construct important nitrogen-containing heterocyclic dihydropyridine compounds under mild conditions is of great significance. This work introduces a new strategy for the solar-driven Hantzsch reaction, leveraging a polyoxometalate-based metal-organic framework (POMOF) as a multifunctional photocatalyst. Unlike conventional thermal approaches, it enables divergent reaction pathways and products under mild ambient conditions, significantly enhancing sustainability and selectivity. Herein, a donor-acceptor structural POMOF, <b>ZnW-TPB</b>, was synthesized from flexible electron-rich <b>TPB</b> photosensitizer, zinc ions, and electron sponge [BW₁₂O₄₀]^5- via the solvothermal method. The combination of REDOX [BW₁₂O₄₀]^5- into a MOF is conducive to charge separation and electron migration, thus resulting in the generation of superoxide radicals (^•O₂^-) at low oxygen concentrations. ^•O₂^- performs the hydrogen abstraction function to remove the H atom from the N-H bond to form stable radical intermediates, which are the key intermediates in the Hantzsch reaction for the synthesis of 1,4-dihydropyridine. Just by simply controlling the reaction time, further oxidation can be achieved to obtain pyridine derivatives.