Photoinduced charge separation of methylphenothiazine in microporous titanosilicate M-ETS-10 (M=Na++K+, H+, Li+, Na+, K+, Ni2+, Cu2+, Co2+) and Na+, K+-ETS-4 molecular sieves at room temperature

Abstract

The photoionization of methylphenothiazine in microporous titanosilicates M-ETS-10 (M \ Na`] K`, H`, Li`, Na`, K`, Ni`, Cu2`and Co2`) and Na,K-ETS-4 molecular sieves with UV irradiation at room temperature is studied. Methylphenothiazine cation radicals are produced in M-ETS-10 molecular (PC`) sieves and are characterized by electron paramagnetic resonance (EPR) and di †use reÑectance (DR) UV-vis spectroscopy. Microporous titanosilicate Na,K-ETS-10 and its ion-exchanged molecular sieves with alkali and transition metal ions are shown to be efficient heterogeneous hosts to accomplish stable net photoinduced electron transfer from methylphenothiazine molecules at room temperature. The photoyield of cation PC 1 radicals was enhanced by incorporation of protons into ion-exchange sites of Na,K-ETS-10. The photoionization efficiency of methylphenothiazine cation radicals decreases in the order H-ETS-10 [ Na,K-ETS-10 [ K-ETS-10 [ Na-ETS-10 [ Ni-ETS-10 [ Li-ETS-10 [ Cu-ETS-10 [ Co-ETS-10. For Na,K-ETSno radical is detected either by EPR or by DR spectroscopy. As the alkyl chain length of the 4ÈPC 1 , PC 1 phenothiazine increases from methyl to hexyl the photoionization yield of H-ETS-10 decreases. Thermogravimetric analysis results support this trend. It is found that the photochemistry in M-ETS-10 and Na,K-ETS-4 molecular sieves is sensitive to the metal ion, pore size and internal void space.

Synthesis of highly active ETS-10-based titanosilicate for heterogeneously catalyzed transesterification of triglycerides

“…It has been demonstrated that application of post-synthetic treatment to titanosilicates can change the state of titanium atoms from Ti(IV) to catalytically active Ti(III) [50]. Such a reduction to paramagnetic Ti in ETS-10 titanosilicates can occur as a result of high-temperature treatment under vacuum [51], treatment with H 2 or CO at moderate to high temperatures [52], ion exchange [53–54], UV [55] or γ-irradiation [51]. To characterize the state of Ti in the titanosilicates participating in catalytic tests and the possible presence of impurities, the EPR spectra of these samples were measured at 70 K (Fig.…”

Photoinduced charge separation at room temperature of N-alkylpyrenes in transition metal ion containing mesoporous SiMCM-41 and MeMCM-41 silica molecular sieves where Me=Ti(IV), V(V), Ni(II), Co(II) and Cu(II)

“…However, the stability of PyC n þ increases from PyC 1 to PyC 16 due to an increased inductive effect in PyC n þ as a function of longer alkyl chain lengths. 39,41,42 A semiquantitative measure of the efficiency of the photoreaction is obtained from the amount of alkylpyrene cation radicals produced relative to the number of alkylpyrene molecules present prior to photoirradiation. The estimated photoconversion is $15%, which is relatively high.…”

Synthesis of Titanosilicates and Related Materials

“…The photoionization of methylphenothiazine in microporous titanosilicates M-ETS-10 (M = N+ + K+, H+, Li+, Na+, K+, Ni+, Cu2+ and Co2+) and Na,K-ETS- 4 with UV irradiation at room temperature has been studied [123]. Methylphenothiazine cation radicals are produced in M-ETS-10 materials but none are detected by EPR or diffuse reflectance UV-Vis spectroscopy on Na,K-ETS-4.…”