Shaping of HKUST-1 via Extrusion for the Separation of CO₂/CH₄ in Biogas

HKUST-1 is a metal-organic framework (MOF) that is widely studied as an adsorbent for CO₂ capture because of its high adsorption capacity and good CO₂/CH₄ selectivity. However, the numerous synthesis routes for HKUST-1 often result in the obtention of MOF in powder form, which limits its application in industry. Here, we report the shaping of HKUST-1 powder via the extrusion method with the usage of bio-sourced polylactic acid (PLA) as a binder. The characterization of the composite was determined by XRD, FTIR, TGA and SEM analyses. The specific surface area was determined from the N₂ adsorption isotherm, whereas the gas adsorption capacities were investigated via measurements of CO₂ and CH₄ isotherms of up to 10 bar at ambient temperature. The material characterization reveals that the composite preserves HKUST-1’s crystalline structure, morphology and textural properties. Furthermore, CO₂ and CH₄ adsorption isotherms show that there is no degradation of gravimetric gas adsorption capacity after shaping and the composite yields a similar isosteric adsorption heat as pristine HKUST-1 powder. However, some trade-offs could be observed, as the composite exhibits a lower bulk density than pristine HKUST-1 powder and PLA has no impact on pristine HKUST-1’s moisture stability. Overall, this study demonstrates the possibility of shaping commercial HKUST-1 powder, using PLA as a binder, into a larger solid-state-form adsorbent that is suitable for the separation of CO₂ from CH₄ with a well-preserved pristine MOF gas-adsorption performance.