Molecular interactions of CO2with the CuBTC metal organic framework: An FTIR study based on two-dimensional correlation spectroscopy

The sorption of Carbon dioxide in the prototype metal-organic framework CuBTC was examined in detail by FTIR spectroscopy. The spectra were collected in-situ under isothermal equilibrium conditions at two different temperatures (308 and 273 K). The results were analyzed by difference spectroscopy (DS) and 2D correlation spectroscopy (2D-COS). In particular, 2D-COS was employed to improve the resolution of the spectral profiles and to verify the occurrence of multiple molecular species. The spectroscopic monitoring of the sorption process provided precise quantitative data as well as relevant molecular-level information. Distinct interaction sites were identified in the framework structure, in agreement with first-principles simulations. A minor fraction of probe molecules characterized by a gas-like behavior was identified by analysis of the n2 frequency range.