A computational study of the interaction of C2 hydrocarbons with CuBTC

Abstract

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.

Experimental and Theoretical Investigation of Ethylene and 1-MCP Binding Sites in HKUST-1 Metal–Organic Framework

“…Due to this fact, ethylene should be allowed to rotate around the z-axis which goes through two copper atoms in the SBU of HKUST-1 (Figure S2). The latter fact was indirectly confirmed by Afonso et al, 25 who obtained almost similar energies for "in-line" and diagonal placement of ethylene with respect to HKUST-1 linkers. In addition, a negative frequency associated with the rotation of ethylene along z-axis was theoretically observed.…”

“…The reported values are in good agreement with previous theoretical studies. 23,25,28 In the cluster approach, the highest binding energy (0.44 eV) is obtained for a SBU of HKUST-1 with ethylene adsorbed on one of the two available Cu sites. However, this energy might be overestimated within the cluster approach since the real periodic structure may impose some constraints on the flexibility of HKUST-1.…”

“…In this work, we discuss the mechanism of ethylene and 1-MCP adsorption on copper centers of the HKUST-1 MOF, a porous structure with open Cu sites. 29 Although several experimental 22,27 and theoretical [23][24][25][26]28 investigations on ethylene in HKUST-1 have been reported, this work presents the first spectroscopic evidence of the 3-dimensional structure of ethylene and 1-MCP bound to Cu ions in this MOF. In situ diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS) was used to monitor the adsorbed ethylene and 1-MCP species.…”

“…Adsorption of ethylene in HKUST-1 and other Cu based MOFs was investigated mainly in frame of ethylene/ethane separation task. − Much less studies were focused on ethylene storage in frame of food preservation technologies. , In the study by Liao et al , a number of metals were screened in M-MOF-74 structure, suggesting copper as a best candidate for high deliverable capacity of ethylene. At the moment, the topic of 1-MCP adsorption in MOFs is significantly underinvestigated.…”

The Adsorption of Small Molecules on the Copper Paddle-Wheel: Influence of the Multi-Reference Ground State

“…Consequently, prediction of adsorption energies of small molecules on this secondary building unit is of great practical interest [ 53 ]. Indeed, there are already a few studies in this direction [ 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 ] performed mainly on the DFT level of theory, and in a few cases are combined with different ab initio approaches [ 63 , 64 , 65 ]. However, working with metal-organic compounds, one should always be aware of possible effects of multi-reference and, associated with that, issues on applicability of different methods.…”