(177a) Self-Disassembly of Two-Dimensional Zeolites in Liquid Polybutadienes

Two-dimensional zeolites (2DZs) are a new class of porous materials with the framework propagating only in two dimensions. 2DZs with a high external surface area and short diffusion length have shown promising applications in high-throughput separation membranes and catalytic reactions involving bulky molecules. The state-of-the-art fabrication method for production of zeolite nanosheets with a well-defined microporous structure is melt-blending of these layered zeolite precursors with polystyrene in a twin-screw extruder. However, this method faces the challenges of high temperature operation, and the potential for damaging the structure of the nanosheets through high energy input. We reported the exfoliation of layered zeolite precursors by suspending them in commercially available telechelic liquid polybutadienes at room temperature without any shear force.

The 2D zeolite nanosheets with an MWW framework have an external surface with 12 membered ring (MR) pockets and 6MR transport limiting apertures, around 0.3 nm, and can potentially separate H₂ from CO₂. MCM-22, a layered precursor of MWW framework, was successfully exfoliated, and single-layer-thick nanosheets were obtained by the novel exfoliation method. The layered precursor MCM-22 was first swollen using a long-chain surfactant (cetyltrimethylammonium bromide) to increase its interlayer spacing. This was followed by hand-mixing the swollen zeolite with a liquid polybutadiene with functional end-groups. The zeolite was intercalated by the polymer and exfoliated merely by hand-mixing. The exfoliated zeolite nanosheets can form a stable suspension in an organic solvent, providing exciting potential for the fabrication of zeolite membranes, composite materials, and hierarchical zeolites. The exfoliation method can also be applied to other 2D zeolite precursors.