Guest Cation Functionalized Metal Organic Framework for Highly Efficient C ₂ H ₂ /CO ₂ Separation

The removal of carbon dioxide (CO₂) from acetylene (C₂H₂) production is critical yet difficult due to their similar physicochemical properties. Despite extensive research has been conducted on metal-organic frameworks (MOFs) for C₂H₂/CO₂ separation, approaches to designing functionalized MOFs remain limited. Enhancing gas adsorption through simple pore modification holds great promise in molecular recognition and industrial separation processes. This study proposes a guest cation functionalization strategy using the anionic framework SU-102 as the prototype material. Specifically, the guest cation Li⁺ is introduced into the skeleton by ion exchange to obtain SU-102-Li⁺. This strategy generates strong interactions between Li⁺ and gas molecules, thereby elevating C₂H₂ uptake to 49.18 cm³ g^-1 and CO₂ uptake to 29.88 cm³ g^-1, marking 20.3% and 36.9% improvements over the parent material, respectively. In addition, ideal adsorbed solution theory selectivity calculations and dynamic breakthrough experiments confirmed the superior and stable separation performance of SU-102-Li⁺ for C₂H₂/CO₂ (25 min g^-1) and C₂H₂ productivity (1.55 mmol g^-1). Theoretical calculations further reveals the unique molecular recognition mechanism between gas molecules and guest cations.