A computational study of the interaction of C2 hydrocarbons with CuBTC

The adsorptions of ethane, ethene, and ethyne over the coordinatively unsaturated sites (CUS) of copper (II) benzene-1,3,5-tricarboxylate (CuBTC) were studied by means of density functional theory (DFT), using both cluster or periodic models. Exchange-correlation functionals from different rungs of the Jacobs ladder of the DFT were used and energies were corrected for the basis superposition error either through extrapolation to the complete basis set limit or upon the consideration of the Counterpoise method. From the calculated data, it was found that the adsorbate to CUS distances decrease in the order ethane > ethene ≈ ethyne and that the strength of adsorption increase in the order ethane to ethyne to ethene. The energies of interactions of ethene and ethyne with the CUS of CuBTC are approximately the double of that calculated for ethane. The calculated adsorption energies and geometries are in very satisfactory agreement with the available experimental results. The results of topological analyses confirm that the unsaturated bonds of ethene and ethyne form open shell like bonds with the CUS while interaction with ethane have predominant closed shell character.