In situ characterization of CO2 adsorption in metal organic frameworks

Abstract

Metal organic frameworks (MOFs) are a class of crystalline nanoporous reticular materials consisting of metallic clusters coordinated to organic linkers, forming 3-dimensional porous structures. In the context of carbon capture and separation (CCS), MOFs are gaining traction as a molecular platform suitable for applications in gas adsorption and separation due to its high surface area, porosity, and tunable pore sizes, leading to improved performance for CO2 storage and separation. Although the performance of these materials is directly linked to their crystalline structure, most of the studies reported so far measure the uptake efficacy from bulk experiments relying on mass gravimetric methods, failing to resolve differences in the micro/nanostructure of these materials. Raman microspectroscopy has been shown to reveal information about the composition, topology, disorder, defects, and host-guest interactions of MOFs [1]. When combined with in situ and in operando approaches, R¬aman microspectroscopy allows the measurement of uptake dynamics in the single crystal level, revealing information about how crystalline defects affect the material efficacy [2]. In this work, we demonstrate how gas adsorption, specifically CO2, can be detected in the micro-scale using confocal Raman spectroscopy. We employ a custom-made reaction cell (Figure 1) to activate, i.e. purge adsorbents from the nanopores, and submit these materials to different environmental conditions. We show how Raman microspectroscopy enables the spatial characterization and time-dependent measurements of gas adsorption. References [1] Tittel, J. , Knechtel, F. & Ploetz, E. . Conquering Metal--Organic Frameworks by Raman Scattering Techniques. Advanced Functional Materials (2023). [2] Fuchs, A et al. Water Harvesting at the Single-Crystal Level. J Am Chem Soc 145, (2023).