Spatial Distribution of Nitrogen Binding Sites in Metal‐Organic Frameworks for Selective Ethane Adsorption and One‐Step Ethylene Purification

Abstract

AbstractThe one‐step purification of ethylene (C2H4) from mixtures containing ethane (C2H6) and acetylene (C2H2) is an industrially important yet challenging process. In this work, we present a site‐engineering strategy aimed at manipulating the spatial distribution of binding sites within a confined pore space. We realized successfully by incorporating nitrogen‐containing heterocycles, such as indole‐5‐carboxylic acid (Ind), benzimidazole‐5‐carboxylic acid (Bzz), and indazole‐5‐carboxylic acid (Izo), into the robust MOF‐808 platform via post‐synthetic modification. The resulting functionalized materials, namely MOF‐808‐Ind, MOF‐808‐Bzz, and MOF‐808‐Izo, demonstrated significantly improved selectivity for C2H2 and C2H6 over C2H4. MOF‐808‐Bzz with two uniformly distributed nitrogen binding sites gave the optimal geometry for selective ethane trapping through multiple strong C−H⋅⋅⋅N hydrogen bonds, leading to the highest C2H2/C2H4 and C2H6/C2H4 combined selectivities among known MOFs. Column breakthrough experiments validated its ability to purify C2H4 from ternary C2H2/C2H4/C2H6 mixtures in a single step.