Molecular Motions of Adsorbed CO2 on a Tetrazole-Functionalized PIM Polymer Studied with 13C NMR

Abstract

The CO2 adsorption in a polymer of intrinsic microporosity (PIM) functionalized by tetrazole (TZPIM) has been studied with in situ 13C nuclear magnetic resonance (NMR) spectroscopy at variable temperature and loading conditions. The CO2 molecules are seen to interact with tetrazole sites through physisorption. The adsorbed system was studied from 8 to 385 K at two loadings of CO2. The 13C NMR resonance lineshapes and relaxation times have been analyzed to give insights into the adsorption process. The CO2 molecules undergo site to site hopping with accompanying CO2 reorientations while adsorbed on TZPIM, resulting in line narrowing starting near 100 K. Correspondingly, the spin echo T2 passes through a minimum at 100 K. The analysis indicates that two kinds of adsorption sites are available.