ETS-10 consists of a single -O-Ti-O- atomic wire which is surrounded by SiO2 frameworks, exhibits unique structure distinct from bulk TiO2. In this structure, each Ti atom can be more efficiently applied as active photocatalytic site. We found that when oxyphilic Cerium were introduced by ion-exchange route, Ce form strong interaction with -O-Ti-O-, adjusting the localized structure while maintain the framework integrity. The XRD showed that the framework integrity, 29Si NMR characterization showed significant chemical shift changes, indicating Ce incorporation induce chemical environment changes in the framework. FT-IR spectra showed the -O-Ti-O- vibration were significantly changed, pristine vibration along the O-Ti-O were reduced while Ce-O-Ti vibration along vertical oritation strengthened, which result from the strong Ce-O-Ti interaction. The resultant Ce-ETS-10 display strong Ce-O-Ti LMCT photo response were proved by SPS (surface photovoltage spectra), which represent efficient charge-hole separation. The formed charge-hole separation was highly originated, which prohibit photo-carrier from recombination, facilitate photocatalytic methane conversion. These phenomenon have not ever seen in other molecular sieves. Pristine ETS-10 do not show any catalytic performance, while the Ce modified ETS-10 exhibit significantly elevated photocatalytic NOCM (non-oxidative methane conversion) performance. During the reaction, methane molecules coupled to form ethane. When more Cerium were introduced to form Ce-O-Ti interaction, the catalytic performance was elevated, and highest methane conversion ratio reach ~ 9.17 μmol g-1 h-1. These atomic LMCT photocatalysis were not well developed in previous studies, this work expand the photocatalysis on molecular sieve or MOF compound.

Cerium's strong interaction with Ti-containing ETS-10 molecular sieve and photocatalytic activation of methane C-H bond

ACS Fall 2021

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