Boosting C2H2/CO2 separation of metal–organic frameworks via anion exchange and temperature elevation

Abstract

Developing new strategies to enhance adsorbents' gas separation performance is highly desirable. In this contribution, we created a post-synthetic modification approach to enhance the C₂H₂/CO₂ separation performance for an ultramicroporous MOF (NKMOF-2) platform that underwent a single-crystal-to-single-crystal in the counter anion exchange process. Substitution of Cl⁻ with BF₄⁻ not only greatly improved the water stability of the NKMOF-2 platform but also enhanced their adsorption capacity and separation performance. Mixture gas breakthrough experiments revealed that the anion exchange strategy was a powerful approach for boosting the selective adsorption of C₂H₂ over CO₂. Moreover, we first observed that the C₂H₂/CO₂ separation performance could be enhanced dramatically by elevating the test temperature. This study not only enriches the toolbox to create efficient MOF adsorbents for gas separation but also provides a fundamental understanding of the enhanced gas uptake and separation performance.