Coordinating Zirconium Nodes in Metal-Organic Framework with Trifluoroacetic Acid for Enhanced Lewis Acid Catalysis

Regulating Lewis acid sites with well-defined electronic state and steric environment is still challenging for achieving high catalytic efficiency. Here we show coordinating zirconium nodes in the typical metal-organic framework known as MOF-545 with the monocarboxylate modulators including trifluoroacetic acid(TFA) or benzoic acid(BA) over meso-tetra(4-carboxyphenyl)-porphine(H2TCPP), denoted as MOF-545-TFA or MOF-545-BA. Impressively, MOF-545-TFA shows the significantly enhanced performance for the catalytic ring-opening reaction of various epoxides with alcohols and good recyclability at 40 degrees C in respect with MOF-545-BA and ZrO2. This mainly originates from the stronger Lewis acidity and more active zirconium sites induced by the electron-withdrawing TFA, resulting in the increased ability for activation of epoxides. This modulation approach is promising for enlarging the toolbox to extend the MOFs-based Lewis acid catalysis.