Pore tuned activated carbons as supports for an enantioselective molecular catalyst
authors Maia, F; Silva, R; Jarrais, B; Silva, AR; Freire, C; Pereira, MFR; Figueiredo, JL
journal JOURNAL OF COLLOID AND INTERFACE SCIENCE
author keywords Mesoporous activated carbons; Textural properties; Enantioselective epoxidation of alkenes; Mn(III) salen complex
keywords MANGANESE(III) SALEN COMPLEXES; SCHIFF-BASE COMPLEXES; HETEROGENEOUS CATALYSTS; DIRECT IMMOBILIZATION; COVALENT ATTACHMENT; EPOXIDATION; OLEFINS; CHLORIDE; STYRENE
abstract The Jacobsen catalyst was immobilized onto four activated carbons with different average pore sizes, achieved by a gasification process followed by molecular oxygen oxidation. The influence of the textural properties of the activated carbon in the immobilization process and in the catalytic performance of the Mn(III) heterogeneous catalysts was investigated in detail. Three different catalytic systems were studied: styrene epoxidation using m-chloroperoxybenzoic acid; 6-CN-2,2-diMeChromene epoxiclation using NaOCl and iodosylbenzene (PhIO) as oxidants. The catalysts tested were active and enantioselective in the three systems studied. Selectivity towards the desired epoxide only decreases in the case of the material with smaller pores, remaining identical to that of the homogeneous phase in all the other materials. The enantiomeric excess values (%ee) for alkene epoxidation increase with the pore size of the heterogeneous catalysts, and these values are even higher than the homogeneous counterparts in the styrene epoxiclation reaction. Total Mn(III) loadings increase with the pore size, as well as their distribution within the carbon porous matrix. Characterization of the activated carbons bearing the immobilized manganese(III) complexes by TPD and XPS point to reaction between carbon surface phenolate groups and the manganese(III) complexes through axial coordination of the metal centers to these groups. (C) 2008 Elsevier Inc. All rights reserved.
publisher ACADEMIC PRESS INC ELSEVIER SCIENCE
issn 0021-9797
year published 2008
volume 328
issue 2
beginning page 314
ending page 323
digital object identifier (doi) 10.1016/j.jcis.2008.09.030
web of science category Chemistry, Physical
subject category Chemistry
unique article identifier WOS:000260845300013
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journal impact factor 5.091
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