2025 AIChE Annual Meeting

(98d) Hybrid Metal-Organic Frameworks (MOFs) for Efficient Gas Separation

Authors

Niket Kaisare - Presenter, Indian Institute of Technology-Madras
Marcello B. Solomon, The University of Sydney
Deanna D'Alessandro, Sydney University
Arvind Rajendran, University of Alberta
Metal-Organic frameworks (MOFs) have emerged as promising candidates for the adsorption of CO2, as they possess tunable properties and adaptable structures [1]. Stability under relevant conditions, higher CO2 selectivity and understanding the influence of water vapor are important criteria for the selection of adsorbents for CO2 capture [2]. ZIF-7 is a hydrophobic MOF of interest, which possesses good stability and exhibits “gate-opening” triggered by guest molecules such as CO2. When the CO2 partial pressure exceeds Pgate of ~0.5 bar, a significant increase in CO2 capacity is observed [3]. Although ZIF-7 shows high CO2 selectivity, only a limited amount of CO2 is captured below Pgate, resulting in the “slip-off” of CO2 [4]. In contrast, conventional MOFs, such as ZIF-90, display a typical Type-I behavior.

In this work, we explore the impact of a mixed-linker synthesis strategy, as reported in Rashidi et al. [5], to analyze hybrid MOFs ZIF-7x-90(100-x), where x and (100-x) corresponds to varying benzimidazole(HbIm) and 2-imidazolecarboxaldehyde (ICA) ligand loadings. The MOFs are comprehensively characterised using structural, spectroscopic and thermophysical techniques. The gas separation behavior and hydrophobicities of the hybrid MOFs are compared with their parent-linker MOFs and their physical mixtures. Our adsorption isotherm studies revealed that higher HbIm linker loadings are required to retain gate-opening flexibilty,whereas higher ICA loading results in an increase in CO2 uptake. The introduction of small amounts of ICA linker significantly enhances the hydrophilicity of hybrid MOFs. Hybrid MOFs demonstrate a range of behaviors (gate opening, selectivity to CO2 and hydrophobicity) depending on the relative amounts of ICA and HbIm linkers. Further, the gas separation performance of hybrid MOFs are evaluated using dynamic column breakthrough (DCB) studies. Hiraide et al. [4] proposed a multi-bed approach to enhance separation efficiency and mitigate the “slipping-off” phenomenon.

Analysis of the synthesized MOFs, comparison with physical mixtures of parent MOFs, and the use of DCB experiments will allow us to simultaneously optimize the material and column for efficient CO2 capture. Quantitative measurements of competitive adsorption of CO2 and water vapor will also be studied under the DCB setup to quantify the influence of humidity on CO2 capture.These combined efforts will provide a deeper understanding of the hybrid MOF strategy, which can be extended to other potential flexible MOFs for efficient gas separation applications.

References:-

[1] Sumida, K., Rogow, D. L., Mason, J. A., McDonald, T. M., Bloch, E. D., Herm, Z. R., Bae, T., & Long, J. R., Chemical Reviews (2011), 112(2), 724–781

[2]Senkovska, I., Bon, V., Mosberger, A., Wang, Y., & Kaskel, S., Advanced Materials (2025), 2414724

[3] Bose, R., Bon, V., Bönisch, N., Selvam, P., Kaisare, N. S., & Kaskel, S., Chemistry of Materials (2023), 35(18), 7825–7838

[4] Hiraide, S., Sakanaka, Y., Kajiro, H., Kawaguchi, S., Miyahara, M. T., & Tanaka, H., Nature Communications (2020), 11(1)

[5] Rashidi, F., Blad, C. R., Jones, C. W., & Nair, S., AIChE Journal (2015), 62(2), 525–537