Selecting Covalent Organic Frameworks for Gas Capture using micro-Raman Spectroscopy

Abstract

Covalent Organic Frameworks (COFs) are a class of organic materials known for their nano and microporous structures. Their properties can be carefully tuned by selecting specific building blocks, which leads to many applications in catalysis, energy storage and gas separation.   One of the most interesting applications of COFs is in $CO_2$ capture and storage (CCS), since $CO_2$ is the major gas released from combustion of fuels and the most important in the greenhouse effect. Specifically, many COFs have been explored for their use in capturing $CO_2$ and separating it from other gases present in flue gas, like $N_2$.   Previous reports have already shown that COFs can be potential candidates for effective and selective gas adsorption. Depending on the pore structure and functionalization, COFs can exhibit higher uptake capacity than Metal Organic Frameworks. However, despite this potential, there aren’t many papers discussing the mechanisms behind the adsorption processes and the possible active sites. Micro-Raman spectroscopy is a powerful tool to probe materials in the microscale. In porous materials, properties like the chemical structure, topology and gas uptake can be detected by observing changes to the Raman Shift and band shape in different conditions.   In this work, we discuss the potential of micro-Raman spectroscopy in the characterization of COFs in the microscale and how it can be leveraged to measure gas adsorption dynamics.