Formation of Metal-Organic Frameworks on a Metal Ion-Doped Polymer Substrate: In-Depth Time-Course Analysis Using Scanning Electron Microscopy.

The growth of metal-organic frameworks (MOFs) on a metal ion-doped polymer as a precursor and support substrate was investigated based on mechanistic and kinetic analyses. The studies were performed by varying the reaction temperature and the concentrations of the organic ligand and nucleation-promoted additive. Using the NH2-MIL-53(Al) framework as a model system, a systematic study of the mechanism of formation of tetragonal- and rod-shaped NH2-MIL-53(Al) crystals on the substrate was performed. The nucleation rate in the early stage of the reaction is a major factor in determining the surface morphology of the resultant NH2-MIL-53(Al) crystal films, as confirmed by changing the concentration of organic ligands and by employing pyridine additives. These results provide a fundamental understanding of the influence of the nucleation rate on the ability to control the morphology and structure of MOF crystal films.

Morphology Control of Metal-Organic Frameworks Based on Paddle-Wheel Units on Ion-Doped Polymer Substrate Using an Interfacial Growth Approach.

A three-dimensional metal-organic framework (MOF) consisting of pillared square-grid nets based on paddle-wheel units was synthesized by interfacial self-assembly of the frameworks on a metal-ion-doped polymer substrate. Although this type of Cu-based MOF is typically synthesized by a two-step solvothermal method, the utilization of a metal-ion-doped polymer substrate as a metal source for the framework allowed for the one-pot growth of MOF crystals on the substrate. The morphology of the obtained MOF crystals could be controlled from tetragonal to elongated tetragonal with different aspect ratios by changing the concentrations of the dicarboxylate layer ligands and diamine pillar ligands. The present approach provides a new route for the design and synthesis of MOF crystals and thin films for future applications such as gas membranes, catalysts, and electronic devices.

Metal nanocrystal/metal-organic framework core/shell nanostructure from selective self-assembly induced by localization of metal ion precursors on nanocrystal surface.

Metal nanocrystal/metal-organic framework core/shell nanostructures have been constructed using metal ion-trapped nanocrystals as scaffolds through a selective self-assembly of framework components on the nanocrystal surfaces. The resulting nanostructures exhibit unique catalytic activity toward nitrophenol analogs.