Tailorable Ionic Frameworks for Selective Gas Adsorption and Separation: Bridging Experimental Insights with Mechanistic Understanding

The selective adsorption and separation of gases using solid adsorbents represent a crucial method for the treatment of toxic gases and the preparation of high-purity gases. The interaction forces between gas molecules and solid adsorbents are influenced by various factors, making precise design of adsorbents to achieve specific gas adsorption a pressing issue that requires urgent attention. In this study, a series of ionic frameworks constructed from Na⁺ and polyoxometalates (POMs) have been constructed through ionic interactions, and possess multiple adjustable parameters. These frameworks exhibit 3D open channels and demonstrate excellent thermal, humidity, and solvent stability. The synthesized ionic frameworks show strong adsorption capabilities for polar gas molecules such as SO₂ and NH₃, while exhibiting negligible adsorption for nonpolar or weakly polar gases like CO, O₂, CH₄, N₂, and H₂, thereby highlighting their significant gas selectivity. Theoretical calculations reveal that the interaction strength between the ionic frameworks and the polar gases is substantially stronger than that for other gaseous species, corroborating the experimental findings. This research not only provides a series of effective absorbents for polar gases but also elucidates key influencing factors on gas adsorption process, thereby inspiring new directions in the development of innovative gas adsorbents.