Intrazeolite Photochemistry. 17. Zeolites as Electron Donors: Photolysis of Methylviologen Incorporated within Zeolites

Abstract

Methylviologen (MV2+) has been adsorbed in a series of zeolites including alkaline ion faujasites (HNaY, LiNaY, NaY, KNaY, RbNaY, CsNaY, and NaX), Naβ, NaMor, and NaZSM-5 by ion exchange. Extra large pore aluminosilicate MCM-41 was also used. The resulting MV2+-doped zeolites have been characterized by an array of analytical and spectroscopic techniques such as chemical analyses, X-ray photoelectron spectroscopy, thermogravimetry−differential scanning calorimetry, diffuse reflectance spectroscopy, and fluorescence, FT-IR, FT-Raman, and MAS 13C NMR spectroscopies. Influence of the confinement and nature of the charge-balancing cation on the molecular properties of MV2+ resulted in shifts of the λmax of the absorption band in the diffuse reflectance spectra from 270 to 280 nm for MV−NaX and 290 nm for MV−NaZSM-5 samples. In addition, changes of the relative intensities of the emission bands at 340 and 420 nm were also noted. The formation of the MV•+ cation radical as a persistent species by thermal treatme...