Defective UiO-66-NH2 (Zr/Ce) catalyzes the synthesis of propylene carbonate under mild conditions

Abstract A series of UiO-66-NH2(Zr/Ce) catalysts were prepared by hydrothermal synthesis and studied its catalytic effect on the reaction of CO2 with propylene oxide. It was found that the addition of Ce ions can effectively reduce the number of UiO-66-NH2 connections. The BET results show that the specific surface area first increases and then decreases with the increase of Ce content. This is inconsistent with the changing trend of TGA, It is possible that the structure of UiO-66-NH2 is destroyed and the particles agglomerate. When the Ce/Zr molar ratio is 5%, UiO-66-NH2 (Zr/Ce) has the highest catalytic activity, because its larger specific surface area and pore volume are more conducive to catalytic reactions. Besides, the catalyst can remain stable after 4 catalytic cycles, but the activity is slightly reduced. It can be seen by in situ DRIFTS that the activated UiO-66-NH2 contains Lewis acid sites and Bronsted acid sites. Finally, we give two possible catalytic mechanisms.