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

Acetylene (C ₂ H ₂ ) 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 C ₂ H ₂ 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 C ₂ H ₂ purification performance. Accordingly, SNNU-37(Fe/Sc), two isostructural MOFs constituted by [Fe ₃ O(COO) ₆ ] or [Sc ₃ O(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 C ₂ H ₂ adsorption amounts of SNNU-37(Fe/Sc) are much higher than those values for C ₂ H ₄ and CO ₂ . Theoretical IAST selectivity values of SNNU-37(Fe) are 2.4 for C ₂ H ₂ /C ₂ H ₄ (50/50, v/v) and 9.9 for C ₂ H ₂ /CO ₂ (50/50, v/v) at 298 K and 1 bar, indicating an excellent C ₂ H ₂ separation ability. Experimental breakthrough curves also revealed that SNNU-37(Fe) could effectively separate C ₂ H ₂ /C ₂ H ₄ and C ₂ H ₂ /CO ₂ under ambient conditions. GCMC simulations further indicate that open Fe or Sc sites and amide groups mainly contribute to stronger adsorption sites for C ₂ H ₂ molecules.