Investigation of Ionic Liquid interaction with ZnBDC-Metal Organic Framework through Scanning EXAFS and Inelastic Neutron Scattering

Zn based Metal-Organic Framework (MOF), Zinc 1,4-benzenedicarboxylate (ZnBDC) has been synthesized and incorporated with ionic liquid (IL) 1-butyl-3 methylimidazolium bromide (BMIMBr) at optimum 50 wt% of IL. Interaction of BMIMBr in the micropores of ZnBDC-MOF is investigated by XPS, scanning EXAFS and inelastic neutron spectroscopy. Significant increase in binding energies of Zn spin-orbit peaks upon IL incorporation is observed from XPS spectra indicating motion of Br(−) anions of the IL BMIMBr towards the unsaturated Zn cluster of ZnBDC-MOF. The k-space periodicity as well as the local coordination geometry of Zn K-edge is investigated from the scanning EXAFS and XANES spectra. Asymmetric oscillation periodicity has been observed from the k-space scanning XANES spectra upon IL incorporation. Difference in peak positions of oxygen and zinc are observed from the R-space scanning EXAFS spectra suggesting change in coordination geometry due to dehydration of Zn(2+) ion in the ZnBDC-MOF upon IL incorporation. Incorporation of IL in the pores of ZnBDC-MOF gives rise to increased scattering intensity in the Inelastic Neutron Scattering (INS) spectra, which is attributed to the displacement of IL ions in the MOF pores.