Raman-spectroscopic evidence of CO2 adsorption in single MOF crystals

Metal organic frameworks (MOFs), a class of nanoporous materials with high surface-to-volume ratio, have potential applications in chemical separations. The interaction of gaseous adsorbates with the adsorbent's atomic constituents plays a key role in determining a MOF's molecular selectivity and diffusivity. Raman micro-spectroscopy is a suitable tool for investigating MOF-adsorbate interactions, including spatial heterogeneity distributions, at the level of single MOF crystals.

In this work, we demonstrate $CO_2$ adsorption in MOFs at the single-crystal level. Specifically, we combine micro-Raman spectroscopy and DFT simulations to investigate $CO_2$-induced spectral changes occurring in spatially isolated crystals of HKUST-1, a copper-based MOF considered for carbon dioxide capture applications. The experiments are carried out in a measurement cell that allows for controlling the gas pressure and temperature. The single-crystal measurement opens a pathway for quantifying crystal-to-crystal variations in the gas adsorption in MOF.