Dynamic hydrophobic hindrance effect of zeolite@zeolitic imidazolate framework composites for CO2 capture in the presence of water

Abstract

For the real industrial process of CO₂ capture, it is still a great challenge for adsorbents to exhibit excellent CO₂ adsorption capacity in the presence of water. By combining a pre-seeding process and a two-step temperature controlling crystallization, a zeolitic imidazolate framework (ZIF-8) shell is introduced on the commercial zeolite adsorbent (5A) core to produce a series of 5A@ZIF-8 composites with an enhanced surface hydrophobicity. Each 5A@ZIF-8 composite exhibits a dynamic hydrophobic hindrance effect for the separation of CO₂ from the simulated humid flue gas (15% CO₂ and 90% humidity at 298 K). Among these, the CO₂ adsorption capacity and the CO₂/H₂O selectivity of 5A@ZIF-8(I) can be as high as 2.67 mmol g⁻¹ and 6.61, respectively, at the optimized adsorption time of 10 min. More importantly, over 10 adsorption–desorption cycles, there is almost no degradation of the adsorption performance. Therefore, the novel strategy of utilizing the dynamic hydrophobic hindrance effect through a core–shell structure would be a good solution for improving the CO₂ separation performance in practical applications.