Elucidating Lewis acidity of metal sites in MFU-4l metal-organic frameworks: N2O and CO2 adsorption in MFU-4l, CuI-MFU-4l and Li-MFU-4l

The interaction strength of N 2 O and CO 2 molecules with different Lewis-acidic sites within MFU-4 l –type metal-organic frameworks was studied via gas sorption measurements and density-functional theory calculations. MFU-4 l comprising Zn–Cl units shows only physisorption of both gases. Introduction of Li into the parent MFU-4 l framework leads to a remarkable increase of binding strength of both N 2 O and CO 2 showing considerable Lewis acidity of Li I centers. Cu I -MFU-4 l shows even stronger binding of N 2 O, as compared to Li-MFU-4 l , whereas CO 2 doesn't bind to Cu I centers. Preferential binding of N 2 O to Cu I centers was also confirmed by in situ synchrotron X-ray powder diffraction measurements. These results show that Cu I -MFU-4 l can be considered as a material for selective N 2 O adsorption.