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

Abstract The one‐step purification of ethylene (C 2 H 4 ) from mixtures containing ethane (C 2 H 6 ) and acetylene (C 2 H 2 ) 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 C 2 H 2 and C 2 H 6 over C 2 H 4 . 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 C 2 H 2 /C 2 H 4 and C 2 H 6 /C 2 H 4 combined selectivities among known MOFs. Column breakthrough experiments validated its ability to purify C 2 H 4 from ternary C 2 H 2 /C 2 H 4 /C 2 H 6 mixtures in a single step.