Molecular engineering of Metal-Organic Frameworks for biogas upgrading: from fundamentals to function

This thesis addresses the role of advanced materials in supporting the energy transition, with particular focus on CO₂ separation and biogas upgrading. Within the framework of the Italian National Recovery and Resilience Plan (PNRR), the project investigates porous materials—Metal–Organic Frameworks (MOFs)—for their potential in sustainable gas separation technologies, both as solid sorbents and as fillers for Mixed-Matrix Membranes (MMMs). The work combines fundamental and application-oriented research. On the fundamental side, it rationalises cooperative adsorption phenomena in flexible MOFs, using F4_MIL-140A(Ce) as a model system. The influence of linker fluorination, metal identity (Ce vs Zr), and mixed-linker architectures on adsorption-induced structural response and CO₂/CH₄ separation are systematically examined, highlighting the non-trivial relationship existing between the structure and the observed adsorption features, aimed at establishing structure–property correlations for the rational design of responsive sorbents. On the applicative side, the research moves to the development of Mixed-Matrix Membranes (MMMs), integrating the model F4_MIL-140A(Ce) with commercial polymers and Polymers of Intrinsic Microporosity. Through MOF particle engineering and targeted surface functionalisation, interfacial MOF–polymer compatibility and separation performance are investigated. Overall, the thesis bridges fundamental understanding and materials engineering, providing foundational strategies for CO₂ separation in biogas upgrading.