Oriented MFI films for gas phase separation, catalysis, and sensing: A review of crystal growth, design, and function enabling

ZSM-5 (Zeolite Socony Mobil - Type 5) is a crystalline aluminosilicate with an MFI (Mobile-type Five) framework with anisotropic distribution of pores and channels along different orientations. A secondary growth method with assistance of pre-deposited seeds has been dominantly utilized to fabricate oriented MFI films to provide the capacity and flexibility of controlling the membrane crystal orientation. Functionally, the straight channels along the b -axis favor mass transfer, while the sinusoidal channels along the a -axis are preferred for product selectivity. The orientation of MFI films affects their application performance in separation, catalytic activities, and selectivities, as well as chemical sensing. In this review, the crystallinity, nanostructure, porosity, and orientation control during the MFI film formation have been surveyed for the latest literature focusing on synthetic approaches, crystal structure designs, and parameter adjustment strategies for tailoring the MFI film structure and orientation distribution. The associated functional enablings have been reviewed and discussed including example devices for capture and separation of various gases such as CO 2 , hydrocarbons (HCs), value-added chemical, and fuel transformation through shape selective catalysis, as well as chemical sensing, as a result of oriented films with different structural and crystalline characteristics. Looking ahead, more research attention is expected for structural and orientational tailoring of MFI and other zeolite films, membranes, and other functional devices for future applications in gas phase sorption, separation, catalysis, sensing, and beyond. Graphical abstract