@article { ISI:000240279200047, title = {Assembly of hydrothermally stable ethane-bridged periodic mesoporous organosilicas with spherical and wormlike structures}, journal = {Microporous and Mesoporous Materials}, volume = {94}, number = {1-3}, year = {2006}, month = {SEP}, pages = {364-370}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Hydrothermally stable periodic mesoporous organosilicas with spherical as well as wormlike frame structures were synthesised by two different synthesis routes using the silsesquioxane precursor, 1,2-bis (triethoxy silyl) ethane (BTEE) and surfactant octadecyl trimethyl ammonium (ODTA), under basic conditions. The materials were characterized by PXRD, SEM, TEM, N-2 adsorption-desorption, FT-IR, Si-29 MAS NMR, C-13 CP MAS NMR and TG-DTA techniques. Characterization techniques revealed that the morphology of the hybrid material prepared from pure silsesquioxane precursor resulted in spherical particles while a combination of tetra ethyl orthosilicate and 1,2-bis (triethoxy silyl) ethane (90:10 ratio) resulted in materials having wormlike structures. Hydrothermal stability of the hybrid material was evaluated by refluxing the sample under boiling water for various time periods and was compared with that of a periodic mesoporous silica material, Si-MCM-41. Results showed that the hybrid material is stable up to 100 h in boiling water, with the existence of d(100) peak, while the mesopore structure of Si-MCM-41 get destroyed even after a 12 h reflux time. The improved hydrothermal stability of the hybrid material is related to the more hydrophobic environment induced inside the pore channels, due to the presence of integrating ethane groups in the wall channels. (c) 2006 Elsevier Inc. All rights reserved.

}, keywords = {hybrid mesoporous materials, Hydrothermal stability, spherical particles, wormlike structures}, issn = {1387-1811}, doi = {10.1016/j.micromeso.2006.04.012}, author = {Shylesh, S. and Jha, Ratnesh Kumar and Singh, A. P.} } @article { ISI:000244798300032, title = {Synthesis of hydrothermally stable aluminium-containing ethane-silica hybrid mesoporous materials using different aluminium sources}, journal = {Microporous and Mesoporous Materials}, volume = {100}, number = {1-3}, year = {2007}, month = {MAR}, pages = {250-258}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Aluminium-containing ethane-silica hybrid mesoporous materials having ethane groups in the frame wall positions are synthesized using aluminium isopropoxide as well as aluminium nitrate as the aluminium sources. The materials were characterized in detail using powder XRD, N-2 adsorption-desorption, SEM, TEM, TG-DTG, TPD, Si-29, C-13 and Al-27 MAS NMR techniques. Characterization techniques revealed that aluminium isopropoxide was the appropriate source for the synthesis of organo aluminosilicas on considering the structural ordering, acidity as well as the percentage of aluminium incorporation into the ethane bridge. Al-27 MAS NMR displays aluminium as tetrahedrally coordinated in both the aluminium-containing organosilicas. Unlike the conventional EtOH-HCl template extraction process, in the present studies, we had used EtOH-NH4OH as the surfactant-extracting medium and chemical analysis results suggest that using this procedure the extent of dealumination can be greatly reduced. XRD and nitrogen physisorption studies further proved that the materials are hydrothermally stable, that the ordered pore channels retains its structure even after 150 h reflux in boiling water, while the conventional Al-MCM-41 catalyst collapsed its mesostructure after 50 h reflux in water. The improved hydrothermal stability of the hybrid materials, even in presence of sodium ions, is attributed to the thick pore walls as well as due to the presence of hydrophobic bridging ethane groups in the wall positions. (c) 2006 Elsevier Inc. All rights reserved.

}, keywords = {Al-HMM, Al-MCM-4l, hybrid materials, Hydrothermal stability}, issn = {1387-1811}, doi = {10.1016/j.micromeso.2006.11.010}, author = {Shylesh, S. and Samuel, Prinson P. and Singh, A. P.} } @article { ISI:000296674400011, title = {Synthesis and characterization of bifunctional ethenylene bridged mesoporous organoaluminosilicates}, journal = {Nanoscience and Nanotechnology Letters}, volume = {3}, number = {4}, year = {2011}, month = {AUG}, pages = {497-502}, publisher = {AMER SCIENTIFIC PUBLISHERS}, address = {26650 THE OLD RD, STE 208, VALENCIA, CA 91381-0751 USA}, abstract = {

Bifunctional mesoporous organosilicas having -CH=CH- bridges and aluminium in tetrahedral coordination with tailorable pore sizes have been synthesized using a one-step templating method using cationic surfactants of different chain lengths. Unlike the conventional EtOH-HCl template extraction process, EtOH-NH(4)NO(3) was used as the surfactant-extracting medium and chemical analysis results suggest that through this procedure the mesoporous structure can be retained and dealumination can be minimized. The surfactant-extracted mesoporous solids display high surface area, pore volume and the pore size of the material varies in the range 2.6-3.6 nm, with respect to the alkyl chain length of the cationic surfactant. XRD and nitrogen physisorption studies further proved that the organosilicas are hydro thermally stable than the conventional Al-MCM-41 materials and their better stability is attributed to the thick pore walls as well as due to the presence of hydrophobic bridging ethenylene groups in the wall positions. The coupling of Al(4) with -CH=CH- bridges offer new prospects for the application of periodic mesoporous organosilicas in heterogeneous catalysis.

}, keywords = {Aluminium, Cationic Surfactants, Hydrothermal stability, Organosilicas}, issn = {1941-4900}, doi = {10.1166/nnl.2011.1196}, author = {Shylesh, S. and Kapoor, Mahendra P. and Juneja, Lekh R. and Srilakshmi, Ch. and Singh, A. P.} } @article { ISI:000287839600014, title = {Tin incorporated periodic mesoporous organosilicas (Sn-PMOs): synthesis, characterization, and catalytic activity in the epoxidation reaction of olefins}, journal = {Catalysis Communications}, volume = {12}, number = {7}, year = {2011}, month = {MAR}, pages = {629-633}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Tin incorporated mesoporous organosilicas (Sn-PMO) having uniform hexagonal arrangements were prepared using alkyl trimethylammonium bromide surfactants under basic reaction conditions. Characterization techniques revealed that the structural ordering, morphology, and the percentage of tin incorporation depend critically on the hydrophobic chain length of surfactants. The Sn-PMO samples are thermally stable up to 500 degrees C under air atmosphere and were hydrothermally stable up to 100 h in boiling water. The organotinsilicates showed excellent catalytic activity and reusability in the epoxidation of norbornene and ciscyclooctene than an Sn-MCM-41 due to organic groups in the frame wall positions and the better accessibility of reactants to the active sites. (C) 2010 Elsevier B.V. All rights reserved.

}, keywords = {epoxidation, Hydrothermal stability, Mesoporous, Organosilica, Sn-MCM-41, Sn-PMO}, issn = {1566-7367}, doi = {10.1016/j.catcom.2010.11.025}, author = {Sisodiya, Sheetal and Shylesh, S. and Singh, A. P.} }