In situ Synchrotron IR Microspectroscopy of CO(2) Adsorption on Single Crystals of the Functionalized MOF Sc(2)(BDC-NH(2))(3)**

Synchrotron radiation (SR) IR microspectroscopy has enabled determination of the thermodynamics, kinetics, and molecular orientation of CO(2) adsorbed in single microcrystals of a functionalized metal–organic framework (MOF) under conditions relevant to carbon capture from flue gases. Single crystals of the small-pore MOF, Sc(2)(BDC-NH(2))(3), (BDC-NH(2)=2-amino-1,4-benzenedicarboxylate), with well-defined crystal form have been investigated during CO(2) uptake at partial pressures of 0.025-0.2 bar at 298–373 K. The enthalpy and diffusivity of adsorption determined from individual single crystals are consistent with values obtained from measurements on bulk samples. The brilliant SR IR source permits rapid collection of polarized spectra. Strong variations in absorbance of the symmetric stretch of the NH(2) groups of the MOF and the asymmetric stretch of the adsorbed CO(2) at different orientations of the crystals relative to the polarized IR light show that CO(2) molecules align along channels in the MOF.