Surfactant-Assisted Morphology Tuning of Ultramicroporous Metal–Organic Frameworks for Efficient Olefine/Paraffin Sieving

Morphology control is a powerful approach to tailor the properties of metal-organic frameworks (MOFs) for separation, catalysis, sensing, and photonics applications. However, previous efforts have primarily focused on microporous systems with pore sizes beyond typical gas dimension thresholds (>0.5 nm); the structural integrity of ultramicroporous MOFs under morphology modulation, particularly the risk of pore destruction or blockage, and their implications for molecular sieving remain insufficiently understood. Herein, we report the morphology control of an ultramicroporous MOF, Co-gallate (3.69 Å), using different kinds of surfactants. By employing cationic (cetyltrimethylammonium bromide, CTAB), nonionic (polyvinylpyrrolidone, PVP), and anionic (sodium dodecylbenzenesulfonate, SDBS) surfactants, diverse morphologies including elongated hexagonal bipyramids, microspheres, and hexagonal nanoplates are obtained. CTAB and PVP direct crystal growth via nucleation-accumulation and template-guided assembly, respectively, but both disrupt the sieving pore channels of Co-gallate due to incomplete coordination and residual surfactant blockage. Whereas SDBS micelles serve as dynamic soft templates that guide anisotropic nanoplate formation without disrupting the intrinsic sieving channels. The prepared nanoplate maintains high C₂H₄/C₂H₆ and C₃H₆/C₃H₈ sieving separation selectivity while accelerating gas adsorption kinetics due to the high aspect ratio, providing a feasible strategy to couple morphology control with preserved ultramicroporosity.