Construction of Sunflower-like Superstructure of CHA Zeolite through Oriented Attachment for Superior CO2 Separation Performance via Thermodynamic–Kinetic Synergistic Adsorption

Pressure-swing adsorption (PSA) is emerging as a promising alternative to chemisorption-based CO2 capture processes due to its high efficiency, low investment, and environmental friendliness. Zeolite, commonly employed as an adsorbent material in PSA processes, exhibits high adsorption selectivity owing to its narrow microporous structure. However, the restricted diffusion kinetics of CO2 gas molecules within the zeolite voids result in decreased separation efficiency and increased regeneration energy consumption. In this study, we synthesized a unique sunflower-shaped superstructure of CHA zeolite, formed through the orientation attachment arrangement of nanocrystal particles, utilizing a nonclassical crystallization mechanism of oriented attachment with the aid of templating agents and crystalline species induction. The formation mechanism of the superstructure has been unveiled. The resulting hierarchical superstructure exhibited both micro- and mesoporous characteristics. Gas adsorption studies revealed a CO2 uptake of 71.14 cm3/g at 298 K and 0.15 bar, which significantly surpassed traditional CHA zeolite with a large-size block structure, outperforming most reported porous materials to date. Predicted by the IAST model, the material demonstrated ultrahigh separation selectivity for CO2/N2 and CO2/CH4 (815 and 264, respectively), underscoring its potential for CO2 capture via the PSA process. Column breakthrough experiments further confirmed the outstanding separation performance of the material for the formation of CO2/N2 and CO2/CH4. Additionally, adsorption kinetics studies revealed that the hierarchical pore structure within the zeolite superstructures greatly enhanced the mass transfer rate and diffusion of gas molecules, leading to a synergistic function of both adsorption thermodynamics and kinetics. These results demonstrate the feasibility of constructing zeolite superstructures to enhance the separation performance of adsorbents, providing a novel synthetic strategy for the development of efficient gas adsorbent materials.