Copper-exchanged zeolites are useful for step-wise methane-to-methanol conversion (MMC). Optimizing the efficiency of these copper-exchanged zeolites for the purposes of MMC is of interest. Experimental characterization of the active sites on copper-exchanged zeolites provides insight into the development of species that could provide improved yields and selectivities. It is common to use electronic structure calculations to explain the origins of peaks in UV-vis spectra. TD-DFT is a less accurate, but affordable computational chemistry method that can be used to study these species. In this work, a systematic examination of TD-DFT was carried out using various classes of density functionals for understanding the UV-vis spectra of the [CuO]+ , [Cu2O]2+, and [Cu3O3 ]2+ species. Restricted active space second-order perturbation theory (RASPT2) was performed on the [CuO]+ system. This was used as a reference in determining the best performing TD-DFT functionals. These functionals were then carried out on the other active site motifs. We find that double hybrids and long-range corrected double hybrid functionals such as MPW2PLYP and ωB2PLYP, respectively, perform well when compared to the RASPT2 calculation on [CuO]+. These functionals account for electron correlation which was found to be of significant importance. The accuracy of the ωB2PLYP functional on the [Cu3O3 ]2+ -MOR in comparison with experimental data serves as the first computational evidence that that [Cu3O3]2+ is likely responsible for the empirically observed spectroscopic data.

Using TD-DFT to characterize active sites on copper-exchanged zeloites

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.