Sorption Enhanced Molecular Sieving MOF Membranes for Propylene-Propane Separation

Propylene is a vital feedstock for producing plastics and chemicals. Propylene feedstocks typically also contain large fractions of propane. Accordingly, propylene/propane separation is an important industrial process. The workhorse separation process of the petrochemical industry is distillation. However separating propylene from propane by distillation is energy-intensive due to their similar boiling points. Membrane technologies are an efficient alternative for this separation. One promising approach is to use advanced materials called metal-organic frameworks (MOFs). MOFs act like sieves that separate molecules based on size and chemical interaction. However, existing MOF membranes show inconsistent performance, poor stability, and difficulty in large-scale manufacturing. This project focuses on the design and synthesis of membranes made from a new MOF material which is more stable and more efficient for propylene/propane separation. This research aims to make propylene/propane separation processes more reliable, efficient, and environmentally friendly. Other benefits of this project include educational opportunities, contributions on membrane technology to a public encyclopedia, and scientific outreach. This project addresses the critical limitations of current metal-organic framework (MOF) membranes for the separation of hydrocarbons. The project will synthesize high-performing polycrystalline membranes with sorption-enhanced molecular sieving selectivity for mixtures of propylene and propane. The focus is on a novel MOF material called ZU-609, which has high adsorption capacity and diffusivity for propylene, but negligible adsorption capacity and low diffusivity for propane. It also shows superior structural stability as compared to other rival materials. These properties make this new MOF material an ideal candidate for membranes with high propylene/propane selectivity (>300) and propylene permeance (>1×10⁻⁸ mol/(m²·s·Pa)), while offering greater reproducibility and scalability than conventional metal-organic framework membranes. The research will synthesize thin, defect-free membranes of the new MOF material on suitable supports by the methods of conventional seeding and reactive seeding with 2D-structured copper oxide substrate, followed by secondary crystal growth. The membranes will then be evaluated for their gas permeation, separation performance, stability, and reproducibility. Comprehensive structural and functional characterization will provide insights into the design of robust, scalable membranes for industrial hydrocarbon separations. Beyond technical innovation, this project will offer comprehensive training for graduate and undergraduate students in membrane science, nanomaterials, and separation technologies through research, coursework, and hands-on lab experience. Additionally, it will conduct public outreach to disseminate information on inorganic membranes, helping to bridge educational gaps and enhance public engagement with science. By improving energy efficiency in chemical separations and promoting education and public awareness of membrane science, this work has the potential for broad scientific and societal impact. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.