A Robust Metal‐Organic Framework With ‘Molecular Gates’ for Efficient Separation of Ethane From Ethylene

Abstract

ABSTRACT Ethane‐selective sorbents can enable single‐step purification of ethylene but remain elusive to date. We report a Zn‐based metal‐organic framework ( ZAI‐3N ) decorated with amino‐based ‘molecular gates’ that exhibit highly selective adsorption of C 2 H 6 over C 2 H 4 . Upon activation, ZAI‐3N (zinc‐adenine‐3‐aminoisonicotinic acid) features contractions of both Zn─N bonds and pores (from 2.009 to 1.914 Å and from 4.88 × 3.40 to 3.47 × 2.75 Å 2 , respectively). At 313 K and 1 bar, ZAI‐3N exhibits an exceptional ratio of 10.6 for C 2 H 6 /C 2 H 4 uptakes and a benchmark selectivity of 11.7, outperforming state‐of‐the‐art porous solids. Synchrotron X‐ray powder diffraction and modelling reveal that the methyl group in C 2 H 6 can trigger amino rotation and facilitate gate opening, while π‐electrons of C 2 H 4 hinder such a process with a notably increased barrier (～5 and 11 kJ mol −1 , respectively). Dynamic breakthrough experiments confirm the efficient separation of C 2 H 6 /C 2 H 4 (v/v = 5/5 and 1/9), affording C 2 H 4 with a high purity of 99.4% in single step with excellent recyclability and an C 2 H 4 productivity of 10.3 mL g −1 . This work demonstrates the judicious choice of ‘molecular gate’ as a promising protocol for challenging industrial gas separations.