An unprecedented -oriented DDR@MWW zeolite hybrid membrane: new insights into H-permselectivities six membered-ring pores

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2020-07, Vol.8 (28), p.1471-1481
• Main Authors: Jang, Eunhee, Lee, Jeong Hyeon, Hong, Sungwon, Jeong, Yanghwan, Kim, Jin Chul, Kim, Dongjae, Baik, Hionsuck, Kim, Eunjoo, Choi, Nakwon, Nam, Jaewook, Cho, Sung June, Kwak, Sang Kyu, Choi, Jungkyu
• Format: Article
• Language: English
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/d0ta03892j

Despite the success of several types of homogeneous zeolite membranes, the manufacturing based on only one type of zeolite largely limits the flexible, reliable synthetic route toward the formation of continuous zeolite membranes. Herein, we demonstrate heterogeneous epitaxial growth of a seed layer using two structurally compatible zeolites. Specifically, MCM-22 (MWW type zeolites) seed layers were epitaxially grown with a synthetic precursor that leads to the DDR type zeolite. The resulting heterogeneous films, referred to as DDR@MWW hybrid films, were continuously formed on porous supports. Furthermore, heteroepitaxial growth of the c -oriented MCM-22 seed layer yielded a preferential c -out-of-plane orientation; accordingly, six membered-ring (6-MR) pores (having a maximum size of ∼0.28 nm) along the c -axis of the MWW and DDR zeolites were, for the first time, aligned in the out-of-plane direction. Subsequently, this good model sample was adopted for determining the H 2 -permselectivities of the 6-MR pores; surprisingly, the 6-MR pores were rather impermeable to both H 2 and CO 2 molecules up to ∼200 °C so that the c -oriented hybrid membrane exhibited modest CO 2 -permselectivities over N 2 (0.364 nm) or CH 4 (0.38 nm) at the expense of reduced CO 2 molar flux. Lastly, this experimental observation was further complemented with rigorous molecular dynamics simulations on well-designed DDR zeolite membranes. A heteroepitaxial growth of a c -oriented MWW zeolite seed layer with a synthetic precursor that led to the synthesis of DDR zeolites resulted in the c -oriented DDR@MWW hybrid membrane.