Evidence of CO2 molecule acting as an electron acceptor on a nanoporous metal-organic-framework MIL-53 or Cr3+(OH)(O2C-C6H4-CO2)

The adsorption mode of CO2 at low coverage in the nanoporous metal benzenedicarboxylate MIL-53(Cr) or Cr3+(OH)(O2C-C6H4-CO2) has been identified using IR spectroscopy; the red shift of the nu(3) band and the splitting of the nu(2) mode of CO2 in addition to the shifts of the nu(OH) and delta(OH) bands of the MIL-53(Cr) hydroxyl groups provide evidence that CO2 interacts with the oxygen atoms of framework OH groups as an electron-acceptor via its carbon atom; this is the first example of such an interaction between CO2 and bridged OH groups in a solid.