In-situ characterization of metal-organic frameworks: A combined DFT and micro-Raman spectroscopy approach

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. Microscale characterization of MOFs can reveal the alteration of material performance caused by both variations in intrinsic and extrinsic parameters. Intrinsic parameters referring to changes in the chemical attributes of the framework, whilst extrinsic to variations in particle size, shape, and surface structure. In this work, we demonstrate how spatially resolved structural information of the MOF framework can be extracted from Raman microspectroscopy of single crystals. Secondly, we show how DFT simulations can be combined with micro-Raman experiments to allow spectral assignment and interpretation. Lastly, we explore how in situ studies of MOFs in different temperatures and pressures can reveal information on $CO_2$ adsorption/desorption dynamics.