Fine-tuning porosity of In-MOFs with ncb topology based on reticular chemistry for one-step purification C2H4 from ternary C2H6/C2H4/C2H2 mixtures

Abstract

One-step purification of C2H4 from ternary C2H6/C2H4/C2H2 mixtures by single adsorbent is of great industrial significance, but few adsorbents can achieve this purpose. Herein, four isoreticular In-MOFs, In-BDC-AINA, In-ATC-INA, In-Fum-INA, and In-Fum-AINA (H2BDC, H2ATC, H2Fum, HINA, and HAINA are 1,4-benzenedicarboxylic acid, 2-amino-terephthalic acid, fumaric acid, isonicotinic acid and 3-amino-isonicotinic acid, respectively), were designed and synthesized by the guidance of reticular chemistry, using the known In-BDC-INA as the platform, through amino modification and ligand shortening approaches. In-ATC-INA and In-BDC-AINA were aminations of H2BDC and HINA, respectively. In-Fum-INA is replacing H2BDC to shorter H2Fum. In-Fum-AINA is obtained by further amination of In-Fum-INA. Due to the molar ratio of isoniacic and dicarboxylic ligands in this series structure is 2/1, they exhibit different site numbers, site distributions, pore sizes and pore volumes after regulation. These frameworks without open metal sites provided the ability of C2H6/C2H4 inversion adsorption. The amino modification and ligand shortening approaches successfully improved the selectivity of C2H2/C2H4, and the equimolar C2H2/C2H4 selectivities of In-ATC-INA (1.82) and In-Fum-INA (2.81) were higher than that of In-BDC-INA (1.73) calculated by IAST method. The breakthrough results show that In-BDC-INA, In-ATC-INA and In-Fum-INA can achieve one-step separation of the ternary C2 mixtures and the C2H4 yields are 0.08, 0.13 and 0.09 mmol/g, respectively, demonstrating that the two approaches have successfully improved the gas separation performance. In addition, these materials possess exceptional thermal and chemical stability, the low-cost ligand used in In-Fum-INA synthesis further enhances its potential application for industrial gas separation.