Enantioselective epoxidation of β-methylstyrene catalyzed by immobilized Mn(salen) catalysts in different mesoporous silica supports

Aqueous Room Temperature Mono-Dehydration of Sugar Alcohols Using Functionalized Yttrium Oxide Nanocatalysts

The aqueous room temperature mono-dehydration of sugar alcohols (D-sorbitol and D-mannitol) was conducted using functionalized yttrium oxide nanocatalysts prepared via sol-gel methods. Materials exhibited high selectivity to mono-dehydration products. Solvent and catalyst effects were also investigated and discussed. The introduction of titanium into the yttrium oxide framework would decrease both substrate conversion and mono-dehydration efficiency. In addition, studies of the catalytic mechanism indicate high mono-dehydration efficiency may come from the stability of the formed intermediate during catalysis. This work provides a highly efficient and benign system for catalytic mono-dehydration of sugar alcohols.

Novel Schiff base Mn(iii) and Co(ii) complexes supported on Co nanoparticles: efficient and recyclable magnetic nanocatalysts for alcohol oxidation

In this study, efficient and highly selective heterogeneous catalysts were developed by immobilization of manganese and cobalt Schiff base complexes on Co magnetite nanoparticles (MNPs).

Novel Mesoporous Silica Materials with Hierarchically Ordered Nanochannel: Synthesis with the Assistance of Straight-Chain Alkanes and Application

The straight-chain alkane-assisted synthesis of hierarchical mesoporous silica materials (MSM) results in variable mesostructures and morphologies due to remarkably different self-assembly routes of template agent from those without the assistance of straight-chain alkanes. The textural properties, particularly pore size, channel structure, morphology, and hierarchical structure of those MSM make them demonstrate peculiar effects in the immobilization of homogeneous catalysts.

Ionic liquid-functionalized graphene oxide as an efficient support for the chiral salen Mn(iii) complex in asymmetric epoxidation of unfunctionalized olefins

Chiral salen Mn(iii) complex covalently grafted on IL-functionalized GO sheet, was a highly efficient, universal and reusable catalyst for asymmetric epoxidation of unfunctionalized olefins using aqueous NaOCl as an oxidant.

A magnetically recyclable Fe3O4@SiO2/Mn(iii) chiral salen complex as a highly selective and versatile heterogeneous nanocatalyst for the oxidation of olefins and sulfides

An efficient system for the selective oxidation of alkenes using TBHP and sulfides using aqueous 30% H₂O₂ catalyzed by a new magnetically recoverable Mn(iii) salen complex with high selectivity and excellent yields was developed.

Chiral Schiff base Ligated Dioxomolybdenum (VI) Complexes and their Asymmetric Catalytic Properties in the Epoxidation of Styrene

Two series of Schiff base dioxomolybdenum (VI) complexes of the general formula [MoO2(L)(MeOH)] (L = D-glucosamine-derived Schiff base) have been synthesised, characterised and their asymmetric catalytic activities evaluated through the epoxidation of styrene. The molybdenum complexes with acetyl-protected D-glucosamine Schiff base ligands exhibited higher enanatioselectivity than those with unprotected sugar ligands. Protecting D-glucosamine by acetyl groups is an effective way to improve asymmetric catalytic epoxidation activities.

Epoxidation of alkenes catalyzed by phenyl group-modified, periodic mesoporous organosilica-entrapped, dimeric manganese-salen complexes

A series of reusable, recoverable, diamine-bridged dimeric manganese-salen complexes were prepared by the encapsulation of homogeneous dimeric Mn(salen) complexes into nanocages of a 3D periodic mesoporous organosilica (PMO) support followed by silylation of the support with organosilane. The composition, structure, morphology, and textural properties of the prepared PMO-entrapped dimeric Mn(salen) complexes were characterized, and their catalytic performances were tested in the epoxidation of alkenes (styrene, cyclohexene, and 1-phenylcyclohexene), with NaClO as an oxygen source and 4-phenylpyridine-N-oxide as an axial ligand. Furthermore, the influences of the textural and morphological properties of the entrapped dimeric Mn(salen) complexes and the key reaction parameters on the catalytic activity and selectivity are discussed. Finally, the reusability of the supported dimeric Mn(salen) complexes was evaluated over three catalytic runs.

Mesoporous silica SBA-15 sheet with perpendicular nanochannels

Free-standing thin sheet form of mesoporous silica materials with perpendicular orientation is a much desired materials for its possible applications in catalysis, mask, and separation. A three component amphiphile system of sodium dodecyl sulfate/hexadecyltrimethylammonium bromide/pluronic-123(C(16)TMAB/SDS/P123) was employed to template the condensation of sodium silicates for the formation of SBA(⊥), a thin sheet of SBA-15 with perpendicular nanochannels. SBA(⊥) can be synthesized at SDS/C(16)TMAB=1.5 and T≥40°C and shows pH-dependent morphology. It has uniform pore size ∼9 nm, homogeneous sheet thickness in the range of 60-300 nm and dimension of several microns. We studied in details the structure and morphology of the SBA(⊥) with variation of three experimental parameters: the SDS/C(16)TMAB ratio, the temperature, and the pH condition in the synthetic gel. It is proposed that the mixed surfactants of SDS and C(16)TMAB form catanionic vesicle in which the P123 and silicates are condensed. The balanced interaction of P123/silicate with the narrow confinement under surfactant bi-layers of C(16)TMAB/SDS promoted the formation of perpendicular nanochannels. Low temperature and pH conditions favor stronger segregation of the PPO and PEO-oligosilicate segments in the SBA(⊥) structure which gives the basis of thickness control of the sheet. The control of structure and morphology are discussed with modern theory of microphase separation in block copolymers under confinement.