Acetic acid-assisted polyhydroxy acid modification of a zirconium-based MOF for synergistic CO2 fixation

The synergistic catalysis involving multiple active sites provides a promising method for improved catalytic activity. In this work, we developed a gentle acetic acid-assisted polyhydroxy acid modification strategy to regulate the coordination environment of a zirconium-based MOF, UiO-66. D-gluconic acid with multiple hydroxyl groups is selected to replace the acetic acid coordinated at the metal nodes of UiO-66 via competitive coordination, allowing for the coexistence of hydrogen bonding donors and Lewis acid sites. The effect of acetic acid and D-gluconic acid separately as modulator and modifier agent to produce linker defects on catalytic properties of UiO-66 was investigated in the cycloaddition of carbon dioxide (CO2) with epichlorohydrin. It was demonstrated that the activity of UiO-66 can be tuned by the amount of D-gluconic acid. Remarkably, the resultant UiO-66-GA-1200, which is modified with 1200 μL of D-gluconic acid, achieves a high catalytic yield for CO2 cycloaddition of epichlorohydrin under 1 bar CO2 and 60 °C. In contrast of pure UiO-66, UiO-66-GA-1200 shows admirable catalytic activities (92–94% yield) even after exposure to humid environment or in simulated flue gas. This work provides a novel method for constructing MOF-based solid acid catalysts and casts a new light on the development of practical CO2 utilization.