Unlocking the scale-up of the benchmark MOFs MIL-53(Al)’s

Environment-friendly synthesis of metal-organic frameworks (MOFs) is crucial to meet growing industrial demand. Here, we present a generalized and scalable route for the production of the prototypical Al-OH chain-based microporous and flexible MIL-53 (MIL = Materials Institut Lavoisier) with various functional groups (X = -H, ˗NH2, ˗NO2, -OH, -COOH)). Until recently, the scale-up of these robust and cost-effective Al-MOFs was hindered by challenges associated with their synthesis and purification, restricting their practical deployment. In this work, we optimized a reflux-based aqueous synthesis method to yield either nano-sized or micron-sized particles. Additionally, we developed a novel, rapid and ambient-pressure exchange process using green solvents to efficiently remove residual free linkers from the MOF pores. This approach affords high-purity MOFs and enables large-scale production with a high space-time yield (ca. 200 kg/m³/day), paving the way for broader implementation. As a proof of concept, we successfully produced MIL-53(Al)-NH2 up to 300g scale maintaining high crystalline quality and adsorption properties comparable to those achieved at smaller scale. Finally, spherical beads of MIL-53(Al)-NH₂ were fabricated using bentonite as binder. These beads exhibited excellent mechanical strength, while retaining their CO₂ adsorption performance, as evidenced by both single-component adsorption isotherms and dynamic breakthrough experiments.