Photoinduced charge separation of N,N,N ',N '-tetramethyl-p-phenylenediamine and N,N,N ',N '-tetramethylbenzidine in synthetic M-mordenite (M = H+, Na+, Na++K+) molecular sieves

Abstract

The photoionization of N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) and N,N,N',N'-tetramethylbenzidine (TMB) in synthetic H-, Na- and Na,K-mordenite molecular sieves was examined at room temperature. It results in the formation of TMPD+ and TMB+ cation radicals, identified by EPR and diffuse reflectance spectroscopy. Alkali metal ion-exchanged mordenites assist in the formation and stabilization of TMPD+ and TMB+ cation radicals compared to H-mordenite. An electron hopping mechanism from TMPD/TMB to the mordenite surface mediated by alkali metal ions is suggested. The photoyield depends on the nature of the photoactive electron donor and the nature of the alkali metal.