Towards applications in catalysis: investigation on photocatalytic activities of a derivative family of the Keplerate type molybdenum–oxide based polyoxometalates

Abstract

The photocatalytic potential of a derivative family of the Keplerate type nano-porous Mo-O based polyoxometalates with general formula [Mo 72 VI Mo 60 V O 372 (L) 30 (H 2 O) 72 ] nÀ (L ¼ CH 3 COO À , SO 4 2À ) (denoted Mo 132 ) has been evaluated by a prototype photocatalytic decoloration reaction of aqueous rhodamine B. The Mo 132 anions are found to be photocatalytically active centers, however they are unstable and subjected to decomposition in the solution form. The introduction of organic counter cations such as tetrabutylammonium (n-Bu 4 N + ) and dioctadecyldimethylammonium (DODA + ) can endow significant stability to the giant anions during the catalytic process. TOC changes and GC/MS measurements were done to identify the degradation products. Among the derivatives, compound 2composed of n-Bu 4 N + and Mo 132 (L ¼ CH 3 COO À ) has been found to be the most active one towards the photocatalytic decoloration of RhB solution. The analytical mechanism indicates that both OH radicals and 1 O 2 participate in the photo degradation process.

{Mo72Fe30} Nanoclusters for the Visible-Light-Driven Photocatalytic Degradation of Organic Dyes

“…While {Mo 72 Cr 30 } clusters were ineffective solar photocatalysts toward RhB degradation under both homogeneous (6%) and heterogeneous (0%) conditions, ammonium {Mo 132 } revealed a moderate efficiency of 48% under the homogeneous condition. Our finding showed that replacing the ammonium countercation by tetra- n -butylammonium, producing { n -Bu 4 N–Mo 132 } as an organic–inorganic hybrid material, promoted the decoloration rate to 60% . Nevertheless, protection of active sites by the long chains of the organic counterion dioctadecyldimethylammonium {DODA–Mo 132 } diminished its efficiency to 20% .…”

“…Our finding showed that replacing the ammonium countercation by tetra-n-butylammonium, producing {n-Bu 4 N−Mo 132 } as an organic−inorganic hybrid material, promoted the decoloration rate to 60%. 31 Nevertheless, protection of active sites by the long chains of the organic counterion dioctadecyldimethylammonium {DODA−Mo 132 } diminished its efficiency to 20%. 18 The vanadium-containing Keplerate {Mo 72 V 30 } was inferior in the dye photodegradation, and a complicated exhibition was observed in RhB solution.…”

“…POMs with a Keplerate structure are giant metal-oxide-based spherical clusters in which 12 pentagonal [(Mo)–Mo 5 O 21 (H 2 O) 6 ] 6– units are linked to each other by 30 linkers such as {Mo V 2 O 4 }, producing a water-soluble spherical {Mo 132 }. The use of Cr III aq and Fe III aq as linkers generates mixed metal Keplerates {Mo 72 M 30 } (M = Cr, Fe) exhibiting unique optical, electronic, and magnetic properties. , They are attractive materials in diverse disciplines, such as chemistry, physics, magnetism, medical sciences, materials science, nanoscience, and even mathematics. − Although catalysis and photocatalysis are well-developed in the POMs community, to our knowledge, the catalysis − and particularly photocatalysis − by Keplerate are still unknown. The crystallinity, morphology, and consequently solubility of some Keplerates could be easily controlled by synthetic procedures.…”

Tetrahedral Keggin Core Tunes the Visible Light-Assisted Catalase-Like Activity of Icosahedral Keplerate Shell

“…As depicted in Figure S19, no significant change in the reaction rate was observed in the presence of methanol as an efficient OH radical scavenger, and O 2 was produced smoothly at the same rate observed in the absence of methanol. The absence of OH radicals in the reaction was also confirmed using terephthalic acid as a photoluminescent OH radical-trapping agent . Upon excitation at 315 nm, no change was observed in the PL intensity of the aqueous suspension (Figure S20), excluding the formation of any OH radical during the photodismutation reaction.…”

Construction and visible‐light photocatalytic performance of carboxyethyltin/transition metal–functionalized wheel‐like tungstophosphates

“…In recent years, POM clusters have received significant attention in photocatalytic degradation of organic pollutants. [14,15] It is necessary to explore new efficient POM-based photocatalysts. In addition, organometal (OM)-functionalized POMs provide a platform for the development of versatile inorganic-organic hybrid materials, [16][17][18][19][20] which may possess a preferable photocatalytic activity.…”