Zeolite-coated 3D-printed gyroid scaffolds for carbon dioxide adsorption

Abstract

3D-printed adsorbents are gaining increased attention owing to their potential in overcoming operational challenges faced by the conventionally structured counterparts. In this work, cylindrical scaffolds of triply periodic minimal surface (TPMS) configuration were synthesized using 3D-printing by stereolithography. This unique gyroid sheet TPMS network was selected as it offers a high surface-area-to-volume ratio. The surface of the scaffolds was modified by a silanization process followed by coating via grafting with zeolite 13X crystals toward CO2 adsorption application. A secondary zeolite coating step was also employed to enhance the zeolite 13X loading, resulting in zeolite loadings of 16 wt% and 23 wt% after the primary and secondary coatings, respectively. Following morphological and structural characterization, the CO2 adsorption performance of the 3D-printed materials was evaluated with respect to adsorption capacity, kinetics, selectivity, and heat of adsorption. Cyclic stability was also assessed over CO2 adsorption–desorption pressure swing adsorption cycles at 25 °C. Comparative analysis showed that the 3D-printed coated samples exhibited higher CO2/N2 selectivity and improved cyclic stability with a slightly lower CO2 adsorption capacity than the zeolite 13X powder. The heat of adsorption ranged from 18 to 41 kJ mol−1 for both the powder and the coated adsorbents, indicating physisorption. The gyroid lattice of the 3D-printed structures, featuring a densely arranged network of smooth, interconnected flow channels, facilitated molecular transport thus yielding higher CO2 adsorption kinetics than the powder. Indicatively, the primary and secondary coatings attained an equilibrium capacity of 4 mmol g−1 at 25 °C in 62 and 57 min, respectively, while the powder required 110 min at the same conditions. The 3D-printed materials exhibited also significantly higher CO2/N2 selectivity values of 569 and 115 at 50 mbar and 1 bar, respectively, for the primary coating sample, and 536 and 73 at 50 mbar and 1 bar, respectively, for the secondary coating one. The findings highlight the potential of 3D-printing to produce coated structured adsorbents with complex geometries for sustainable CO2 capture and gas adsorption processes.