Photoswitchable Metal-Organic Framework as a Smart Nanoreactor for Ultraviolet Light-Enhanced Confined Catalysis

Chemical reaction confined within nanospace provides a feasible approach for modulation of catalysis. However, the confinement effect is typically limited to a fixed rate and/or selectivity once nanohost is chosen. Herein, we developed a photo-responsive metal-organic framework (MOF) as a smart nanoreactor to realize ultraviolet (UV) light-enhanced confined catalysis of Knoevenagel condensation. Photo-responsive MOF of Zn-ADA was thus prepared by solvothermal strategy where azobenzene-4,4ʹ-dicarboxylic acid (ADA) was used as the photoactive linker to coordinate with zinc nitrate. Characterization results suggested that UV light could decrease the pore size of Zn-ADA due to trans -to- cis photoisomerization of azobenzene in ADA linker. It enforced the proximity between substrates and catalytic groups within the confined space, and thus enhancing the confinement effect on Knoevenagel condensation. The UV light-enhanced confined catalysis enabled the translation of light stimulus into chemical signal, which may open up new control on the basis of the specific reaction field.