Enhancing CO2 solubility for efficient carbon capture via self-assembly deep eutectic solvents on MOF-808

Abstract

The capture of CO2 from flue gas has emerged as the most effective technology for carbon reduction. The relatively low partial pressure of CO2 in flue gas necessitates the development of CO2-selective adsorbents, which provide a direct pathway to obtaining pure CO2 in one-step, thereby reducing energy consumption. Herein, an amino-rich deep eutectic solution (DES) is dispersed on the surface of formate ligand-removed MOF-808 using a self-assembly approach for post-combustion carbon capture. The high solubility of DES towards CO2 enables the composite to effectively capture CO2, with MOF-808 serving as a porous gas storage tank. Material characterization confirms the loading of DES on the surface of MOF support while retaining its microporous structure. Owing to their unique CO2 solution-diffusion mechanism, DES-modified adsorbents exhibit promising performance on CO2 capacity, kinetics, CO2/N2 selectivity, and isosteric heat. The optimized sample DES-2@MOF-808-FR demonstrates a notable CO2 adsorption capacity of 4.16 mmol/g at 298 K and 1 bar. When tested with simulated flue gas (15 vol% CO2), it maintains a working capacity of 2.86 mmol/g and a CO2/N2 selectivity of 1184, surpassing most of existed materials. DES-2@MOF-808-FR can also retain its capacities after 10 adsorption/desorption cycles in simulated flue gas. This solution-based modification approach circumvents the challenges associated with precise structural control of the adsorbent, thereby facilitating potential industrial applications.