CO 2 Captured in Zeolitic Imidazolate Frameworks: Raman Spectroscopic Analysis of Uptake and Host–Guest Interactions

Zeolitic imidazolate frameworks (ZIFs) exhibit enhanced selectivity and increased CO 2 uptake due to the incorporation of functional imidazolate units in their structure as well as their extensive porosity and ring flexibility. In situ Raman investigation of a representative host compound, ZIF‐69, in practical CO 2 pressure and temperature regimes (0–10 bar and 0–64 °C) correlates well with corresponding macroscopic CO 2 sorption data and shows clear clear spectroscopic evidence of CO 2 uptake. Significant positive shift of the 159 cm −1 phenyl bending mode of the benzimidazole moiety indicates weak hydrogen bonding with CO 2 in the larger cavities of the ZIF matrix. Raman spectroscopy is shown to be an easy and sensitive tool for quantifying CO 2 uptake, identifying weak host–guest interactions and elucidating CO 2 sorption mechanism in ZIFs.