Chemical engineering of triazine and β-ketoenamine units in covalent organic frameworks with synergistic effects for boosting C2H2 and CO2 separation

Abstract

Efficient gas separation, particularly the selective separation of C₂H₂ and CO₂, is of paramount importance for environmental sustainability and industrial efficiency. However, the achievements of efficient separation of C₂H₂/CO₂ lies in the development of adsorbents with appropriate pore size and specific recognition sites. Covalent organic frameworks (COFs) have demonstrated high potential for gas separation benefitting from their tunable pore structures, high surface areas, and selective adsorption properties. Herein, we report the synthesis of a series of COFs by engineering triazine and β-ketoenamine functional groups. The triazine and β-ketoenamine in TTA-TFP-COF exhibit a novel synergistic effect through complementary π–π interactions and potential charge transfer mechanisms, enabling an exceptional acetylene adsorption capacity of 111.0 cm³ g⁻¹ at 298 K, surpassing the performance of most other COFs. Density functional theory (DFT) calculations revealed that the enhanced adsorption mechanism was driven by the synergistic interaction of the functional groups. Furthermore, dynamic breakthrough experiments confirmed the robust and selective separation performance of TTA-TFP-COF for C₂H₂/CO₂ mixtures, maintaining stability over multiple adsorption–desorption cycles. The above findings highlight the potential of rationally designed COFs as high-performance adsorbents for industrial gas separation, offering a promising route to enhance C₂H₂ purification and promote sustainable industrial practices.