Chlorination of a Zeolitic-Imidazolate Framework Tunes Packing and van der Waals Interaction of Carbon Dioxide for Optimized Adsorptive Separation

Molecular separation of carbon dioxide (CO2) and methane (CH4) is growing interest for biogas upgrading, capture utilization, synthesis purification natural gas. Here, we report a new zeolitic-imidazolate framework (ZIF), coined COK-17, with exceptionally high affinity the adsorption CO2 by London dispersion forces, mediated chlorine substituents imidazolate linkers. COK-17 type flexible Zn(4,5-dichloroimidazolate)2 SOD topology. Below 200 K it displays metastable closed-pore phase next to its stable open-pore phase. At temperatures above K, always adopts structure, providing unique sites selective packing through van der Waals interactions groups, lining walls micropores. Localization adsorbed molecules Rietveld refinement X-ray diffraction data periodic density functional theory calculations revealed presence nature different sites. In agreement experimental data, grand canonical Monte Carlo simulations isotherms CH4 in confirmed role functions linkers demonstrated superiority compared other adsorbents such as ZIF-8 ZIF-71.