Synthesis and Functionalization of Oriented Metal-Organic-Framework Nanosheets: Toward a Series of 2D Catalysts

Synthesis of metal-organic frameworks (MOFs) is based on coordination-driven self-assembly of metal ions and organic ligands. However, to date, it remains difficult to adjust the coordination behaviors of MOFs and then control geometric shapes of nanostructures; especially their morphologies in 1D nanofibers or 2D nanosheets have seldom been explored. Here, a facile route at room temperature and ambient pressure is reported for the preparation of copper-based MOFs with low-dimensional shapes (i.e., nanofibers, nanorods, nanosheets, and nanocuboids), via thermodynamic and kinetic controls over the anisotropic growth. Importantly, the as-prepared 2D MOF nanosheets with monocrystalline nature (100% exposed {010} facets) provide a material platform to the fabrication of 2D supported metal nanocatalysts. First, the MOF nanosheets can serve as a self-templating solid precursor to prepare different CuO and CuO-Cu2O nanocomposites, or even Cu metals via thermolysis or reduction under controlled atmospheres. Upon their formation, second, ultrafine noble metal nanoparticles (e.g., Au, Ag, Pt, Pd, Au0.4Pt0.6, Au0.4Pd0.6, and Au0.3Pt0.3Pd0.4) can be exclusively anchored on the external surfaces of the MOF nanosheets. To show their open accessibility, catalytic activities of the derived catalysts have been evaluated using CO2 hydrogenation and 4-nitrophenol reduction in gas phase and liquid phase, respectively.