Redox-Active Zeolitic Transition Metal Oxides Based on ε-Keggin Units for Selective Oxidation

Abstract

The design and development of zeolitic transition metal oxides for selective oxidation are interesting due to the combination of the redox properties and microporosities. Redoxactive zeolitic transition metal oxides based on ε-Keggin iron molybdates were synthesized. O 2 can be activated by the materials via an electron-transfer-based process, and the materials can be oxidized even at room temperature. The materials are oxidized and reduced reversibly while the crystal structures are maintained. V is uniformly incorporated in the materials without changing the basic structures, and the redox properties of the materials are tuned by V. The materials are used as robust catalysts for ethyl lactate oxidation to form ethyl pyruvate using O 2 as an oxidant.

Aerobic Alcohol Oxidation by a Zeolitic Octahedral Metal Oxide based on Iron Vanadomolybdates Under Mild Conditions

“…Furthermore, ion‐exchange was able to replace the cation species of the material, which would change the property of the material. According to the previous study, Fe‐exchange would enable the material for the O 2 activation [13] . Herein, we found that introducing Fe by the ion‐exchange process would enhance the catalytic activity of the material.…”

“…NH 4 MoFeO was able to activate O 2 at room temperature [13] . O 2 adsorbed in NH 4 MoFeO with oxidation of Mo and Fe during the adsorption.…”

“…MoFeVO and MoFeO were synthesized by the hydrothermal method, which was basically the same to the reported method with slight modification [13] . Herein, Na 2 MoO 4 ⋅ 2H 2 O and NaVO 3 were used as the Mo source and the V source, respectively, to produce the resulting materials with Na + as the cation.…”

“…Synthesis of other materials based on ϵ ‐Keggin POM unit, such as NaMoZnO , NH 4 MoZnO , [12] MoMnO , [12] and MoCoO , [22] were on the basis of the previous methods. Fe exchange experiment was carried out at room temperature in aqueous solution for NH 4 MoZnO , which was also according to the previous method [13] …”

“…Among these iso‐structural materials, (NH 4 ) 2 Fe II 0.6 H 11.7 [Fe II 2.0 Mo VI 1.1 Mo V 10.9 O 40 ] and (NH 4 ) 2 Fe II 0.6 H 8.5 [Fe II 1.0 Mo VI 2.7 Mo V 8.9 V IV 1.4 O 40 ], denoted as NH 4 MoFeO and NH 4 MoFeVO , are interesting. The Fe and Mo based ZOMOs can activate molecular oxygen at room temperature [13] . Therefore, we assume that the material based on the similar compositions are active for the low temperature catalytic oxidation of organic compounds.…”