Discrete complexes immobilized onto click-SBA-15 silica: controllable loadings and the impact of surface coverage on catalysis.
Discrete complexes immobilized onto click-SBA-15 silica: controllable loadings and the impact of surface coverage on catalysis.
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DOI：
10.1021/ja210400u
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发表时间：
2012-02-08
影响因子：
15
通讯作者：
Stack, T. Daniel P.
中科院分区：
文献类型：
--
作者：
Nakazawa, Jun;Smith, Brian J.;Stack, T. Daniel P.
Azidopropyl functionalized mesoporous silica SBA-15 were prepared with variable azide loadings of 0.03 – 0.7 mmol g−1 (ca. 2 – 50% of maximal surface coverage) through a direct synthesis, co-condensation approach. These materials are functionalized selectively with ethynylated organic moieties through the copper-catalyzed azide alkyne cycloaddition (CuAAC) or “click” reaction. Specific loading within a material can be regulated by either the azide loading or limiting the alkyne reagent relative to the azide loading. The immobilization of ferrocene, pyrene, tris(pyridylmethyl)amine (TPA), and iron porphyrin (FeTPP) demonstrates the robust nature and reproducibility of this two step synthetic attachment strategy. Loading-sensitive pyrene fluorescence correlates with a theoretically random. surface distribution, rather than a uniform one; full site-isolation of tethered moieties ca. 15 Å in length. occurs at loadings less than 0.02 mmol g−1. The effect of surface loading on reactivity is observed in oxygenation of SBA-15-[CuI(TPA)]. SBA-15-[MnII(TPA)]-catalyzed epoxidation exhibits a systematic dependence on surface loading. A comparison of homogeneous, site-isolated and site-dense complexes provides insight into catalyst speciation and ligand activity.
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作者：
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通讯作者：
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