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.