Single-file diffusion and its influence on membrane gas separation: A case study on UTSA-280
Journal
Journal of Membrane Science
Journal Volume
706
Start Page
122920
ISSN
0376-7388
Date Issued
2024-07
Author(s)
Cheng-Hsun Hsu
Chia-Yi Lin
Hsiang-Yu Wang
Pei-Ying Lin
Chia-Hui Chuang
Li-Wei Hsiao
Cheng-chau Chiu
DOI
10.1016/j.memsci.2024.122920
Abstract
Gas permeation in metal-organic framework-based (MOF-based) membranes is often elucidated through the solution-diffusion model, where the adsorption and diffusion of gases play equally vital roles. This study draws attention to a unique phenomenon known as single-file diffusion (SFD) occurring within MOF membranes that possess ultramicropores with dimensions comparable to the gas molecules themselves. When SFD takes place, the separation performance becomes solely reliant on the adsorption quantities on the feed side of the membrane. As a proof of concept, we fabricated a UTSA-280 membrane and subjected it to testing using gas mixtures of CO2/N2 and CO2/CH4. Two crucial observations substantiate the occurrence of single-file diffusion. Firstly, in the gas mixtures, the diffusion coefficients of N2 or CH4 were observed to align closely with that of CO2, despite the intrinsic diffusion coefficients of CO2, N2, and CH4, as determined from single-gas permeation experiments, exhibiting differences. Secondly, the CO2 mole fractions within the adsorption phase closely mirrored those in the gas phase on the permeate side. Given the high adsorption selectivity of UTSA-280 for CO2, the UTSA-280 membrane delivers outstanding permeation selectivity for CO2/N2 (611) and CO2/CH4 (80.7). Our experimental findings are supported by mesoscale kinetic Monte Carlo simulations, which confirmed the relation between the CO2 compositions in the adsorption phase on the feed side and in the gas phase on the permeate side. Furthermore, density functional theory calculations revealed high energy barriers associated with CO2 surpassing its counterparts, rendering such processes unfavorable, thereby reinforcing our experimental findings regarding single-file diffusion.
Subjects
CO2 separation
Kinetic Monte Carlo
Membrane gas separation
Metal-organic framework
Single-file diffusion
SDGs
Publisher
Elsevier BV
Description
Article number 122920
Type
journal article