TY  - JOUR
A1  - Göbel, Ronald
A1  - Stoltenberg, Marcus
A1  - Krehl, Stefan
A1  - Biolley, Christine
A1  - Rothe, Regina
A1  - Schmidt, Bernd
A1  - Hesemann, Peter
A1  - Taubert, Andreas
T1  - A Modular Approach towards Mesoporous Silica Monoliths with Organically Modified Pore Walls: Nucleophilic Addition, Olefin Metathesis, and Cycloaddition
JF  - European journal of inorganic chemistry : a journal of ChemPubSoc Europe
N2  - We have synthesized mesoporous silica (monoliths) with defined surface chemistry by means of a number of addition reactions: (i) coupling of an isocyanate to a surface-immobilized thiol, (ii) addition of an epoxide to a surface-immobilized thiol, (iii) cross-metathesis between two olefins, and (iv) Huisgen [2+3] cycloaddition of an alkyne-functionalized silica monolith with an azide. Functionalization of the mesopores was observed, but there are significant differences between individual approaches. Isocyanate and epoxide additions lead to high degrees of functionalization, whereas olefin metathesis and [2+3] cycloaddition are less effective. We further show that the efficiency of the modification is about twice as high in mesoporous silica particles than in macroscopic silica monoliths.
KW  - Mesoporous materials
KW  - Hybrid materials
KW  - Surface chemistry
KW  - Click chemistry
KW  - Nucleophilic addition
Y1  - 2016
U6  - https://doi.org/10.1002/ejic.201500638
SN  - 1434-1948
SN  - 1099-0682
VL  - 6
SP  - 2088
EP  - 2099
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Goebel, Ronald
A1  - Hesemann, Peter
A1  - Friedrich, Alwin
A1  - Rothe, Regina
A1  - Schlaad, Helmut
A1  - Taubert, Andreas
T1  - Modular thiol-ene chemistry approach towards mesoporous silica monoliths with organically modified pore walls
JF  - Chemistry - a European journal
N2  - The surface modification of mesoporous silica monoliths through thiol-ene chemistry is reported. First, mesoporous silica monoliths with vinyl, allyl, and thiol groups were synthesized through a sol-gel hydrolysis-poly-condensation reaction from tetramethyl orthosilicate (TMOS) and vinyltriethoxysilane, allyltriethoxysilane, and (3-mercaptopropyl) trimethoxysilane, respectively. By variation of the molar ratio of the comonomers TMOS and functional silane, mesoporous silica objects containing different amounts of vinyl, allyl, and thiol groups were obtained. These intermediates can subsequently be derivatized through radical photoaddition reactions either with a thiol or an olefin, depending on the initial pore wall functionality, to yield silica monoliths with different pore-wall chemistries. Nitrogen sorption, small-angle X-ray scattering, solid-state NMR spectroscopy, elemental analysis, thermogravimetric analysis, and redox titration demonstrate that the synthetic pathway influences the morphology and pore characteristics of the resulting monoliths and also plays a significant role in the efficiency of functionalization. Moreover, the different reactivity of the vinyl and allyl groups on the pore wall affects the addition reaction, and hence, the degree of the pore-wall functionalization. This report demonstrates that thiol-ene photoaddition reactions are a versatile platform for the generation of a large variety of organically modified silica monoliths with different pore surfaces.
KW  - mesoporous materials
KW  - photochemistry
KW  - sol-gel processes
KW  - surface chemistry
Y1  - 2014
U6  - https://doi.org/10.1002/chem.201403982
SN  - 0947-6539
SN  - 1521-3765
VL  - 20
IS  - 52
SP  - 17579
EP  - 17589
PB  - Wiley-VCH
CY  - Weinheim
ER  -