Well-Dispersed ZIF-8 on Randomly Lamellar Clinoptilolite as an Adsorbent Showing Enhanced CO₂/CH₄ Selectivity for Biogas Gas Separation

The removal of CO₂ from biogas is critically important for environmental protection and energy applications yet remains technically challenging in the chemical industry. In this work, novel composite adsorbents featuring ZIF-8 uniformly dispersed on randomly oriented clinoptilolite lamellae (LCP) were designed and fabricated through a straightforward composite method. The synthesis sequentially incorporated metal precursors into LCP via ion exchange and salt addition and then introduced organic ligands to generate ZIF-8. Comprehensive characterizations, including XRD, FT-IR, N₂ adsorption-desorption isotherms, SEM, and TG analyses, confirmed the physicochemical properties and structural features of the composites. The synthesized Zn-LCP/ZIF-8 materials exhibited exceptional CO₂/CH₄ separation performance, demonstrating ultralow CH₄ adsorption capacity (<0.1 mmol/g) coupled with superior CO₂/CH₄ selectivity (≈28). Complementary molecular simulations using Material Studio software provided mechanistic insights into the adsorption and separation behavior, which further confirmed the superiority of the composite structure in CO₂/CH₄ separation. These results establish an effective strategy for biogas purification, while offering new perspectives for enhancing the CO₂/CH₄ adsorption selectivity.