Polymer-Assisted Space-Confined Strategy for the Foot-Scale Synthesis of Flexible Metal–Organic Framework-Based Composite Films

At the gas-liquid interface, the confined synthesis of metal-organic framework (MOF) films has been extensively developed by spreading an ultrathin oil layer on the aqueous surface as a reactor. However, this interface is susceptible to various disturbances and incapable of synthesizing large-area crystalline MOF films. Herein, we developed a polymer-assisted space-confined strategy to synthesize large-area films by blending poly(methyl methacrylate) (PMMA) into the oil layer, which improved the stability of the gas-liquid interface and the self-shrinkage of the oil layer on the water surface. Meanwhile, the as-synthesized MOFs as a quasi-solid substrate immobilized the edge of the oil layer, which maintained a large spreading area. Thanks to this synergistic effect, we synthesized the freestanding MOF-based film with a foot-level (0.66 ft) lateral dimension, which is the largest size reported so far. Besides, due to the phase separation of the two components, the MOF-PMMA composite film combined the conductivity of MOFs (1.13 S/m) with the flexibility of PMMA and exhibited excellent mechanical properties. More importantly, this strategy could be extended to the preparation of other MOFs, coordination polymers (CPs), and even inorganic material composite films, bringing light to the design and large-scale synthesis of various composite films for practical applications.