Salt-free synthesis of Cu-BTC metal-organic framework exhibiting mesoporosity and enhanced carbon dioxide adsorption

Cu-BTC (HKUST-1) metal-organic framework (MOF) in crystalline powder form was prepared by using a copper mesh as the metal source without involving any additional metal precursor, and its performance was evaluated for CO₂ capture. The crystalline structure, morphology, textural characteristics and surface chemical properties of the synthesized HKUST-1 samples were examined by XRD, SEM, N₂ physisorption, and FTIR. The MOF synthesized using the salt-free method exhibited high crystallinity, small size (~2 μm) and uniform crystal morphology, and mesoporosity. The CO₂ adsorption on the MOF was assessed at various temperatures and evaluated with respect to capacity, selectivity, kinetics, and heat of adsorption. Compared to HKUST-1 synthesized by the conventional method, the mesh-derived MOF exhibited a higher CO₂ adsorption capacity (48% higher at 1 bar and 25 °C), increase in CO₂/N₂ adsorptive selectivity (~11%), as well as faster adsorption kinetics (by 73%). The heat of adsorption was found to increase as well particularly at higher coverages. The obtained CO₂ uptake (~5.2 mmol/g at 1 bar and 25 °C) is among the highest reported for this MOF. The synthesis procedure presented here encompasses high yield (up to 85%), while it requires fewer chemicals and generates less waste compared to the solvothermal approach. As such, it holds the potential to facilitate scaled-up production in a cost-effective and greener way, as the demand for highly efficient porous materials for gas adsorption applications, including CO₂ capture and H₂ storage, is anticipated to significantly increase in the near future.