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.

We report a new paradigm for the synthesis of metal−organic framework (MOF) crystals with controlled thickness by utilizing interfacial self-assembly of frameworks on metal ion-doped polymer precursors. The approach involves preparation of metal ion-doped polymer precursors through ion-exchange reactions and synthesis of MOF crystals by immersion into solutions containing organic ligands. The thickness of the resulting MOF crystals can be readily controlled by the number of doped-metal ions in the polymer precursors. MOF crystals could be very important and potentially useful for applications, and the present approach based on interfacial self-assembly could significantly advance MOF crystal preparation techniques.