Dimensional impact of metal-organic frameworks in catalyzing photoinduced hydrogen evolution and cyanosilylation reactions

Abstract

Metal-organic frameworks (MOFs) have been widely studied as heterogeneous catalysts. Compared to the MOFs with three-dimensional (3D) topologies, two-dimensional (2D) MOF nanosheets can allow facile access to the active sites on their external surface, thus having huge potentials in catalysis. Herein, we fabricate 2D MOF nanosheets, UiO-67-NS, as photocatalyst for H2 evolution reaction, and study their photocatalytic performance in relation to their 3D bulk counterparts (UiO-67). The UiO-67-NS exhibit an 84-fold increase in photocatalytic efficiency compared to UiO-67. Postsynthetic cation grafting of the UiO-67-NS with titanium leads to further enhancement in photocatalytic efficiency, giving a hydrogen evolution rate of up to 393 μmol g-1 h-1, which is 13-times higher than that of the nongrafting nanosheets under the same condition. Our results indicate that the 3D-to-2D dimensionality reduction can be a viable strategy for the development of MOFs as efficient photocatalysts. In addition, we have demonstrated that the improvement of catalytic performance based on the strategy of 3D-to-2D framework dimensionality reduction can be easily extended to heterogeneous cyanosilylation reaction.