Abstract
We report a theoretical study of water adsorption on coordinatively unsaturated sites (cus's) in a metal-organic framework (MOF) compound CuBTC. The reliability of the density functional theory (DFT) based methods and dispersion-corrected DFT-D schemes for the description of cus sites was investigated with respect to the accurate references CCSD(T)/CBS data.
The accuracy of both DFT and DFT-D methods was found to be insufficient. The proposed DFT/CC correction scheme gave the results in excellent agreement with the reference CCSD(T)/CBS data DFT/CC calculations performed for the periodic CuBTC model gave RCu-OH2 = 2.19 angstrom and -Delta H-ads = 49 kJ mol(-1) both in very good agreement with available experimental data.
The interaction of the first water molecule with the paddle-wheel unit is about 5 kJ mol(-1) stronger than the interaction of the second water molecule with the same-paddle-wheel unit.