Construction of Octadentate Carboxylate-Based Metal-Organic Framework for Effective Acetylene Purification

The development of high-performance acetylene (C₂H₂) adsorbents remains challenging, primarily due to the mutual repulsion between their adsorption capacity and selectivity. To address this challenge, we propose introducing multiple host-guest interaction sites into an octadentate carboxylate-based metal-organic framework (MOF, Cu-ETTB) featuring elevated specific surface area and substantial pore dimensions, achieved through the implementation of a polyaromatic octatopic carboxylic acid linker (H₈ETTB). Due to its dense aromatic rings and carboxylate oxygen sites, the obtained Cu-ETTB framework exhibits excellent C₂H₂ adsorption capacity (108 cm³ g^-1) and equimolar C₂H₂/CO₂ selectivity (19.2) under ambient conditions (298 K, 1 bar). Breakthrough experiments confirm a dynamic C₂H₂ adsorption capacity reaching 84.4 cm³ g^-1 for C₂H₂/CO₂ segregation. Grand Canonical Monte Carlo (GCMC) simulations reveal that aromatic rings and oxygen sites within Cu-ETTB selectively capture C₂H₂ via framework-C₂H₂ interactions and C₂H₂-C₂H₂ intermolecular interactions, while effectively excluding CO₂. Furthermore, the Cu-ETTB adsorbent exhibits robust thermal/chemical stability and outstanding recyclability, holding great promise for practical separation processes. This study provides new insights for designing MOF-based adsorbents with tailored functionality, enabling the selective capture of target gases for efficient purification.