Investigating the role of activation in CO2 and N2 adsorption in Flexible MOFs

Metal Organic Frameworks (MOFs) are a class of porous materials composed by a metal center and an organic linker that rise as candidates for gas capture and separation, due to its characteristics of pore shape/size, selectivity, active sites and confinement effects of the material. Besides all the pore features, some MOFs also present Open Metal Sites (OMS) which can coordinate to small molecules, such as H2O and CO2, which are important gases in the greenhouse effect. Pre-activation is often an important step before the analysis with the means remove guest molecules and gases that can be inside the pores post-synthesis or after contact with other media, such as the air, which can lead to a loss of the crystallinity or a phase change of the material.

In this work, we explore the adsorption of $N_2$ and $CO_2$ in ZnBDC(TED)0.5, a flexible MOF, to understand how this material behaves upon adsorption of these two gases. Using Raman micro-spectroscopy, a powerful tool that gives fingerprint vibrational information, we indicate variations in the structure through shifts, changes in intensities and shape of the Raman bands. The experiments are performed on an environment controlled cell, additionally, we also explore specially how pre-activation of these materials can impact the results upon chemical and physisorption and performed DFT simulations of the Raman Spectrum for ZnBDC(TED)0.5 with different conditions of adsorption of $N_2$ and $CO_2$.