UiO-66(NH₂)-based metal organic framework interpenetrated polyurethane matrix as a catalytic microreactor for...

Microreactors, characterized by their internal microstructures and high surface-area-to-volume ratios, offer significant advantages in chemical synthesis, including enhanced heat and mass transfer, precise reaction control, and scalability. In this work, a polyurethane foam (PUF)-based catalytic microreactor was fabricated through the in-situ incorporation of the zirconium-based metal-organic framework UiO-66-NH₂ during foam formation. Structural characterization confirmed the successful integration of UiO-66-NH₂ within the porous polyurethane matrix while preserving its crystallinity, thermal stability, and catalytic functionality. The resulting MOF-PUF composite exhibited improved surface area and hierarchical porosity, having an average pore diameter of 5.59 nm compared with pristine polyurethane foam, providing accessible catalytic sites and efficient mass transport. The hybrid microreactor was successfully applied to Knoevenagel condensation reactions for the synthesis of α-cyanoacrylonitriles and to the one-pot multicomponent synthesis of 2-amino-4H-benzo[b]pyran derivatives. A broad range of aromatic aldehydes was converted under mild conditions in ethanol, affording the desired products in 80-99% yields. The catalyst also demonstrated excellent reusability, retaining more than 90% of its initial catalytic activity after three consecutive cycles with minimal structural changes. The results suggest that the UiO-66-NH₂/PUF composite can serve as an effective and recyclable microreactor for Knoevenagel condensation and the synthesis of 2-amino-4H-benzo[b]pyran derivatives.