MIL-101 as Reusable Solid Catalyst for Autoxidation of Benzylic Hydrocarbons in the Absence of Additional Oxidizing Reagents

Abstract

Materiaux de l'Institute Lavosier-101 (MIL-101) promotes benzylic oxidation of hydrocarbons exclusively by molecular oxygen in the absence of any other oxidizing reagent or initiator. Using indane as model compound, the selectivity toward the wanted ol/one mixture is higher for MIL-101(Cr) (87% selectivity at 30% conversion) than for MIL-101(Fe) (71% selectivity at 30% conversion), a fact that was associated with the preferential adsorption of indane within the pore system. Product distribution and quenching experiments with 2,2,6,6-tetramethyl-1-piperidinyloxy, benzoic acid, and dimethylformamide show that the reaction mechanism is a radical chain autoxidation of the benzylic positions by molecular oxygen, and the differences in selectivity have been attributed to the occurrence of the autoxidation process inside or outside the metal organic framework pores. MIL-101 is reusable, does not leach metals to the solution, and maintains the crystal structure during the reaction. The scope of the benzylic oxidation was expanded to other benzylic compounds including ethylbenzene, n-butylbenzene, iso-butylbenzene, 1bromo-4-butylbenzene, sec-butylbenzene, and cumene.

MIL-101 promotes the efficient aerobic oxidative desulfurization of dibenzothiophenes

“…9, 46 BET surface areas and pore volumes obtained after synthesis were around 1,850 m 2 g -1 and 1.12 cm 3 , respectively. 23 These differences can influence the interaction of the MOF with molecular oxygen and can also modify the polarity of the internal voids of the material.…”

“…23 In addition, MIL-101 solids exhibit large pores (free diameters of 29 and 34 Å) with microporous windows of 12 and 16 Å, respectively, allowing the adsorption of DBT derivatives into their cavities. It has been frequently observed that, in order to be used as catalyst, MOFs have to be submitted to an activation process to remove co-adsorbed water and solvent molecules and to generate coordinatively unsaturated sites around the metal centers.…”

“…This HOO · radical will be formed from O 2 ·-by protonation by moisture present in the medium and constitutes and experimental evidence of the involvement of the generated reactive oxygen species by acting MIL-101(Cr) solid as initiator. 23 Selective radical quenching experiments using p-benzoquinone 59 and 1035 cm -1 have been detected when the sample was exposed to O 2 flow at 120 ○ C. These bands have been attributed to peroxo and superoxo species, respectively.…”

N‐Hydroxyphthalimide Anchored on Diamond Nanoparticles as a Selective Heterogeneous Metal‐free Oxidation Catalyst of Benzylic Hydrocarbons and Cyclic Alkenes by Molecular O2

“…The 1‐hydroperoxy IB cannot be quantified by GC owing to its decomposition. Therefore, the reaction mixture was treated with triphenylphosphine at 80 °C to promote decomposition of the hydroperoxide and, then, the formation 1‐hydroxy‐1‐IB, together with 1‐phenyl‐1‐isobutanol was quantified together with triphenylphosphine oxide and 1‐phenyl‐2‐methyl‐1‐propanol . Benzoic acid is a secondary product, coming from oxidation of phenyl isopropyl ketone.…”

Interfacial CoOx Layers on TiO2 as an Efficient Catalyst for Solvent‐Free Aerobic Oxidation of Hydrocarbons

“…[28][29][30][31][32][33][34][35][36][37][38][39] Normally, these reactions are performed at high temperatures to activate the stable sp 3 -hybridized CÀH bonds. [28][29][30][31][32][33][34][35][36][37][38][39] Normally, these reactions are performed at high temperatures to activate the stable sp 3 -hybridized CÀH bonds.…”