In Situ Synthesis of Multivariate Zeolitic Imidazolate Frameworks for C<sub>2</sub>H<sub>4</sub>/C<sub>2</sub>H<sub>6</sub> Kinetic Separation
Ki Jin Nam, Hyun Jung Yu, Seungho Yu, Jeongho Seong, Seok‐Jhin Kim, Ki Chul Kim, Jong Suk Lee
Abstract
Abstract Herein, a new approach for the in situ synthesis of zeolitic imidazolate framework (ZIF) nanoparticles with triple ligands, referred to as Sogang ZIF‐8 (SZIF‐8), is reported for enhanced C 2 H 4 /C 2 H 6 kinetic separation. SZIF‐8 consists of tetrahedral zinc metals coordinated with tri‐butyl amine (TBA), 2,4‐dimethylimidazole (DIm), and 2‐methylimidazole (MIm). SZIF‐8(x) with different DIm contents in x (up to 23.2 mol%) are synthesized in situ because TBA preferably deprotonates DIm ligands due to the much lower p K a of DIm over MIm, allowing for the Zn‐DIm coordination. The Zn‐DIm coordination reduces the window size of ZIF‐8 with suppressed linker flipping motion due to bulky DIm ligands and simultaneously enhances the interfacial interaction between 6FDA‐DAM polyimide (6FDA) and SZIF‐8 via electron donor–acceptor interactions. Consequently, 6FDA/SZIF‐8(13) mixed matrix membrane exhibits an excellent C 2 H 4 permeability of 60.3 Barrer and C 2 H 4 /C 2 H 6 selectivity of 4.5. The temperature‐dependent transport characterization reveals that such excellent C 2 H 4 /C 2 H 6 kinetic separation is attained by the enhancement in size discrimination‐based energetic selectivity. Our hybrid multi‐ligand approach can offer a useful tool for the fine‐tuning of molecular structures and textural properties of other metal organic frameworks.