Fabrication of Ultrathin 2D Cu-BDC Nanosheets and the Derived Integrated MOF Nanocomposites

Freestanding 2D nanosheets with many unprecedented properties have been used in a myriad of applications. In this work, 2D copper-bearing metal-organic frameworks (MOFs; viz., Cu-BDC) nanosheets are successfully fabricated via a facile and benign methodology through using Cu2O nanocubes (approximate to 60 nm) as a confined metal ion source and 1,4-benzenedicarboxylic acid (H2BDC) as an organic linker. The Cu2O nanocubes gradually release Cu+ ions which are further oxidized by the dissolved oxygen and serve as nutrients for construction of 2D frameworks. In contrast, the conventional solvothermal synthesis with copper salt exclusively yields bulk Cu-BDC with edge dimensions of 2-10 mu m. Interestingly, the as-prepared Cu-BDC nanosheets show ultrathin thickness, oriented growth, and excellent crystallinity, which can be exploited as a platform for the design of a series of 2D-integrated nanocatalysts by loading various metal nanocrystals such as Au, Ag, Pt, and Ru, with 3-mercaptopropionic acid as molecular link. In addition, it is found that Cu-BDC/M composites with highly accessible active sites on the surface exhibit high catalytic activity in several condensation reactions between benzaldehyde and primary amines. The findings offer an alternative strategy for rational design and synthesis of 2D MOF nanosheets and the derived 2D nanocomposites for catalytic applications.