Electronic Structure of Zn+-Modified Zeolite: A Density Functional Theory Study of Ferrierite

摘要

Density functional theory (DFT) calculations were used to study the monovalent Zn+ cation exchanged in an extra-framework position of zeolite ferrierite. A single Zn+ was found to be paramagnetic. Two Zn+ cations combined to form a subnano-sized dimeric species [Zn-Zn](2+) which fits into the eight- or ten-membered rings (8MR or 10MR, respectively) of ferrierite: Within the [Zn-Zn](2+) pair, two cations were bound via a covalent s-s bond. Upon the pair forming, a huge stabilization was observed, linked with a decrease in potential energy by 235-296 kJ/mol, depending on the location of Zn+ in the framework. The [Zn-Zn](2+) species is an electron paramagnetic resonance (EPR) silent insulator with a band gap of 4.82 eV. Because 8MR and 10MR are present in a majority of zeolite structures, we predict that the Zn-modified electron-rich materials. can be fabricated from almost any stable aluminum-rich zeolite. Because Of the strong tendency for the conversion of Zn+ to Zn2+, the Zn+ - modified zeolites are strong solid Lewis bases with promising catalytic properties.