Bead-like MOF nanosheet assemblies for high-loading thin mixed-matrix membranes in molecular separation

Metal–organic framework (MOF)-based molecular separation membranes have great potential in the recovery of organic solvents by pervaporation. Nevertheless, fabricating high-loading mixed-matrix membranes (MMMs) without interfacial defects typically requires a thicker membrane, which inevitably increases mass transfer resistance. Herein, bead-like ZIF sheets (BZIFs) were fabricated by inducing the in-situ growth of stacked ultrathin ZIF sheets (∼20 nm) surrounding the surface of polypyrrole (PPy) nanotubes. Benefiting from the shear-driven orientation of BZIFs and the resulting reduction in coating hysteresis, a defect-free BZIFs/polydimethylsiloxane (PDMS) membrane was fabricated by conventional doctor-blade coating. These MMMs achieved a high loading capacity (up to 44.4 wt%) while retaining a thin thickness of 1.1–2.6 μm. The BZIFs/PDMS exhibited a permeation flux of 2.6 kg m⁻² h⁻¹ alongside a separation factor of 54 when separating a 1% butanol/water solution at 40 °C, and its separation performance remained stable over long-term operation. The two-dimensional lamellar stacked filler design strategy proposed in this study offers a universal approach for fabricating high-loading hybrid materials, while providing valuable insights into the directional design of filler microstructures and the efficient modification of polymers.