Hierarchically Porous Structured Adsorbents with Ultrahigh Metal–Organic Framework Loading for CO<sub>2</sub> Capture
Solomon K. Gebremariam, Anish Mathai Varghese, Sebastian Ehrling, Yasser Al Wahedi, Ahmed AlHajaj, Ludovic F. Dumée, Georgios N. Karanikolos
Abstract
High Resolution Image Download MS PowerPoint Slide Metal–organic frameworks (MOFs) have emerged as promising candidates for CO 2 adsorption due to their ultrahigh-specific surface area and highly tunable pore-surface properties. However, their large-scale application is hindered by processing issues associated with their microcrystalline powder nature, such as dustiness, pressure drop, and poor mass transfer within packed beds. To address these challenges, shaping/structuring micron-sized polycrystalline MOF powders into millimeter-sized structured forms while preserving porosity and functionality represents an effective yet challenging approach. In this study, a facile and versatile strategy was employed to integrate moisture-stable and scalable microcrystalline MOFs (UiO-66 and ZIF-8) into a poly(acrylonitrile) matrix to fabricate readily processable, millimeter-sized hierarchically porous structured adsorbents with ultrahigh MOF loadings (∼90 wt %) for direct industrial carbon capture applications. These structured composite beads retained the physicochemical properties and separation performance of the pristine MOF crystal particles. Structured UiO-66 and ZIF-8 exhibited high specific surface areas of 1130 m 2 g –1 and 1431 m 2 g –1, respectively. The structured UiO-66 achieved a CO 2 adsorption capacity of 2.0 mmol g –1 at 1 bar and a dynamic CO 2 /N 2 selectivity of 17 for a CO 2 /N 2 gas mixture with a 15/85 volume ratio at 25 °C. Furthermore, the structured adsorbents exhibited excellent cyclability in static and dynamic CO 2 adsorption studies, making them promising candidates for practical application.