Amide-Functionalized Metal–Organic Frameworks Coupled with Open Fe/Sc Sites for Efficient Acetylene Purification

• Published in: Inorganic chemistry 2021-12, Vol.60 (23), p.18473-18482
• Main Authors: Fan, Shu-Cong, Li, Yun-Tong, Wang, Ying, Wang, Jia-Wen, Xue, Ying-Ying, Li, Hai-Peng, Li, Shu-Ni, Zhai, Quan-Guo
• Format: Article
• Language: English
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.1c03044

Acetylene (C2H2) purification is of great importance for many chemical synthesis and processes. Metal–organic frameworks (MOFs) are widely used for gas adsorption and separation due to their variable structure and porosity. However, the exploitation of ideal MOF adsorbents for C2H2 keeps a challenging task. Herein, a combination of open metal sites (OMSs) and Lewis basic sites (LBSs) in robust MOFs is demonstrated to effectively promote the C2H2 purification performance. Accordingly, SNNU-37­(Fe/Sc), two isostructural MOFs constituted by [Fe3O­(COO)6] or [Sc3O­(COO)6] trinuclear clusters and amide-functionalized tricarboxylate linkers, were designed with extra-stable 3,6-connected new architectures. Derived from the coexistence of high-density OMSs and LBSs, the C2H2 adsorption amounts of SNNU-37­(Fe/Sc) are much higher than those values for C2H4 and CO2. Theoretical IAST selectivity values of SNNU-37­(Fe) are 2.4 for C2H2/C2H4 (50/50, v/v) and 9.9 for C2H2/CO2 (50/50, v/v) at 298 K and 1 bar, indicating an excellent C2H2 separation ability. Experimental breakthrough curves also revealed that SNNU-37­(Fe) could effectively separate C2H2/C2H4 and C2H2/CO2 under ambient conditions. GCMC simulations further indicate that open Fe or Sc sites and amide groups mainly contribute to stronger adsorption sites for C2H2 molecules.