Proximity Effect on the Reactivity of Dioxygen Activated over Distant Binuclear Fe Sites in Zeolite Matrices

0555822 - ÚFCH JH 2023 RIV US eng J - Článek v odborném periodiku
Sklenák, Štěpán - Groizard, T. - Jirglová, Hana - Sazama, Petr - Dědeček, Jiří
Proximity Effect on the Reactivity of Dioxygen Activated over Distant Binuclear Fe Sites in Zeolite Matrices.
Journal of Physical Chemistry C. Roč. 126, č. 10 (2022), s. 4854-4861. ISSN 1932-7447. E-ISSN 1932-7455
Grant CEP: GA ČR(CZ) GA19-02901S; GA ČR(CZ) GF21-45567L
Výzkumná infrastruktura: e-INFRA CZ - 90140
Institucionální podpora: RVO:61388955
Klíčová slova: dioxygen * iron compounds * zeolite matricečs
Obor OECD: Physical chemistry
Impakt faktor: 3.7, rok: 2022
Způsob publikování: Omezený přístup

Distant binuclear cationic M(II) centers in transition-metal-exchanged zeolites were shown to activate dioxygen by its splitting at room temperature to form a pair of very active oxygen species (i.e., α-oxygens) able to subsequently oxidize methane to methanol at room temperature. Selective oxidations of methane and other hydrocarbons are of extreme importance because of their potential for the transformation of hydrocarbons to valuable products. The reactivity of the α-oxygens with dihydrogen was investigated to obtain insight into the reactivity of these unique species. The reduction of Fe(IV) O centers of pairs of distant α-oxygen atoms is a model reaction that allows for the study of the effect of the proximity of the other Fe(IV) O site on the reactivity of the α-oxygen. The reduction by dihydrogen is also the key reaction for the quantification of these unique sites by temperature-programmed reduction (TPR) techniques. Our study reveals that (i) there is no direct concurrent reaction of both the Fe(IV) O centers of pairs of the distant α-oxygen atoms with a molecule of dihydrogen, (ii) first, one Fe(IV) O site of a pair of the distant α-oxygen atoms reacts with H2(g) to form a water molecule, which is adsorbed on the Fe(II) cation while the other Fe(IV) O site is intact. Afterward, one of the two H atoms of the adsorbed water molecule migrates to yield two Fe(III)OH groups, which subsequently react with another molecule of dihydrogen to give two water molecules, each adsorbed on one Fe(II) cation, (iii) an isolated Fe(IV) O site is reduced by the same mechanism as the first Fe(IV) O site of a pair of the distant α-oxygen atoms to yield H2O adsorbed on the Fe(II) cation, and (iv) lower reducibility of the Fe(IV) O centers of pairs of the distant α-oxygen atoms with respect to the isolated Fe(IV) O sites.
Trvalý link: http://hdl.handle.net/11104/0330275