Shaping of metal-organic frameworks by direct ink writing for carbon capture applications

Given the present challenge posed by global warming, a considerable number of porous materials have been tested and proven effective as CO2 adsorbents in recent years. However, most of them exhibit significant drawbacks in terms of environmental impact and operating conditions, which serve to limit the positive impact of these solutions. Metal-Organic Frameworks (MOFs) represent a novel class of functional materials with an inherently robust porous structure and high surface area. Synthesis of MOFs typically yields the product in the form of fine powders, requiring a shaping step before the adsorbent can be used in industrial applications. In this context, Additive Manufacturing processes offer great geometrical flexibility, allowing direct design of high-performance structured adsorbents with optimized architectures. This work explores shaping strategies for CeMIL-140, a novel MOF with exceptional CO2 selectivity and obtainable from a green synthesis in aqueous medium, by Direct Ink Writing (DIW). While CeMIL-140 offers advantageous properties for the intended application, as a partly organic material it poses challenges due to limitations on the use of traditional binding agents, in particular regarding post-printing heat-treatment temperatures and chemical environment (e.g. pH). Clay-based binders as well as sol-gel approaches were investigated to incorporate MOF particles into highly porous 3D-Printed monoliths with high surface area and optimal accessibility, while achieving sufficient mechanical stability via mild heat treatments to preserve the integrity of the structured adsorbent.