(248e) Design of Porous Hybrid Composites with Dual-Adsorption Capacity for Carbon Capture

Metal organic frameworks (MOFs) have gained significant recognition in their applications for capture due to their capability to physically capture CO₂ molecules within their pore structure. They possess high surface area, and their surface can be functionalized with amines to increase their efficiency. However, amine functionalization leads to the binding of the amine group to the open metal sites which is responsible for carbon capture via physisorption and thus, adsorption of CO₂ occurs through chemisorption over the bonded amine groups. In this study, we encapsulated HKUST-1 crystals in porous silica spheres using a one-step facile aerosol-assisted synthesis technique. This ship-in-a-bottle approach is such that, as the silica growth occurs in the heating zone due to evaporation induced hydrolysis and condensation, the HKUST-1 crystals are entrained within the porous spherical matrix. Characterization results shows that the structural properties and crystallinity of the HKUST-1 particles remained unaltered within the porous shell, after encapsulation. We showed the accessibility of the entrained HKUST-1 to CO₂ capture at atmospheric pressure and 35 ℃ at dry conditions, using a thermogravimetric analysis setup. The results showed that the HKUST-1 crystals are fully accessible to CO₂ molecules with an adsorption capacity of 1.78 mmol/g at 30 wt% of HKUST-1 (PS30HKT). When normalized, the PS30HKT has an adsorption capacity of 5.93 mmol/g which is comparable to that of bulk HKUST-1 (reference sample) with CO₂ adsorption capacity of 5.62 mmol/g (wt%). This shows that the encapsulated HKUST microcrystals are fully accessible to CO₂ through the narrow pores of the PS30HKT without loss in adsorption performance. This unique composite morphology has potential for further functionalization to improve the CO₂ capture of the composite material such that, the porous silica matrix can be functionalized with amine groups while the surface and pore structure of the encapsulated HKUST-1 crystals remained pristine. In essence, we will have a hybrid adsorbent that can capture CO₂ via physisorption over the entrained HKUST-1 crystals while the amine-functionalized silica pores can simultaneously adsorb CO₂ via chemisorption.