Solvent Regulation in Layered Zn-MOFs for C2H2/CO2 and CO2/CH4 Separation

The development of alternative adsorptive separation technologies is extremely significant for the separation of C₂H₂/CO₂ and CO₂/CH₄ in the chemical industry. Emerging metal-organic frameworks (MOFs) have shown great potential as adsorbents for gas adsorption and separation. Herein, we synthesized two layered Zn-MOFs, UPC-96 and UPC-97, with 1,2,4,5-tetrakis(4-carboxyphenyl)-3,6-dimethylbenzene (TCPB-Me) as a ligand via the solvent regulation of the pH values. UPC-96 with a completely deprotonated ligand was obtained without the addition of acid, exhibiting two different channels with cross-sectional sizes of 11.6 × 7.1 and 8.3 × 5.2 Ų. In contrast, the addition of acid led to the partial deprotonation of the ligand and afforded UPC-97 two types of channels with cross-sectional sizes of 11.5 × 5.7 and 7.4 × 3.9 Ų. Reversible N₂ adsorption isotherms at 77 K confirmed their permanent porosity, and the differentiated single-component C₂H₂, CO₂, and CH₄ adsorption isotherms indicated their potential in C₂H₂/CO₂ and CO₂/CH₄ separation.