Green and sustainable metal–organic framework catalysts for biodiesel production: Progress and energy circularity perspectives

The global transition toward low-carbon and resource-efficient energy systems has increased the demand for sustainable catalytic technologies in biodiesel production. This review systematically screened 179 potentially relevant peer-reviewed articles published between 2015 and 2025 and critically synthesized the core experimental studies directly related to metal–organic framework (MOF) and MOF-derived heterogeneous catalysts for esterification and transesterification in biodiesel production. The discussion focuses on material design, synthesis strategy, catalytic mechanisms, catalyst stability, process intensification, techno-economic analysis (TEA), life-cycle assessment (LCA), and circular bioeconomy integration. Key focus areas include material design, process intensification and integration of sustainability metrics. Zr- and Co-based frameworks (e.g., UiO-66, ZIF-67) repeatedly exhibit conversion yields > 90%–99% with good recyclability. Functionalised MOFs (sulfonic acid, heteropolyacid, ionic liquid) enable one-step conversion of high-free-fatty-acid feedstocks. Green synthesis strategies (solvent-free, aqueous, supercritical CO 2 ) reduce energy and solvent footprints relative to conventional solvothermal methods. Available TEA and LCA studies suggest that sustainable synthesis, solvent recovery, catalyst reuse, and regeneration strategies can substantially reduce cost and environmental burdens, although quantitative benefits remain strongly dependent on catalyst type, synthesis route, system boundary, and process scale. Future directions include artificial intelligence, photocatalysis and electrocatalysis for multifunctional MOFs powered by renewables. This review bridges materials science and process engineering to position MOFs as enablers of scalable, carbon-neutral biodiesel technologies aligned with global sustainability agendas.