Morphology‐Engineered ZIF Nanosheet Membranes With 4‐Membered‐Ring Apertures for Propylene/Propane Separation

ABSTRACT

Precise hydrocarbon separations remain a major challenge for membrane technologies because molecular discrimination is often limited by poor control over pore accessibility and transport pathways in conventional mixed‐matrix membranes (MMMs). Here, we report a morphology‐engineering strategy that transforms the intrinsic pore anisotropy of ZIF nanoparticles into selectively exposed 4‐membered‐ring apertures within two‐dimensional (2D) nanosheets, which are subsequently assembled into highly oriented 2D ZIF MMMs. The pore system is reactivated through a soft chemical activation that removes residual surfactants while preserving structural integrity and solution processability. A shear‐flow‐induced pre‐alignment process directs the in‐plane orientation of 2D ZIF nanosheets within the polymer matrix, aligning the aperture channels parallel to the gas transport direction to maximize hydrocarbon molecular recognition. Multiscale characterization and simulations reveal a direct structure–transport relationship linking nanosheet orientation, aperture‐specific diffusion, and macroscopic separation behavior. The resulting 2D ZIF‐8 nanosheet MMMs exhibit enhanced mechanical robustness together with outstanding hydrocarbon separation performance, delivering a 332% increase in C ₃ H ₆ permeability and a 274% improvement in selectivity relative to the pure polymer membrane. This work provides a general strategy for programming pore accessibility and orientation in 2D MOF MMMs for precise molecular separations.