Nature of hydroxy groups in MCM-41

Abstract

The type and concentration of hydroxy groups in MCM-41 as a function of the Si : A1 ratio have been investigated and compared with amorphous Si/Al oxide. Three hydroxy groups at 3745, 3715 and 3530 cm-' were observed in the IR spectra of siliceous MCM-41. For Al-containing samples the intensity of the bands at 3715 and 3530 cm-' increased with increasing A1 concentra-Paper 6/01807F;

Incorporation of Copper in SiBEA Zeolite as Isolated Lattice Mononuclear Cu(II) Species and its Role in Selective Catalytic Reduction of NO by Ethanol

“…The appearance of narrow bands at 3,736 and 3,710 cm -1 related to isolated internal silanol groups and of a broad band at 3,520 cm -1 due to H-bonded SiOH groups in SiBEA reveals the presence of vacant T-sites associated with silanol groups, as shown earlier [11]. The incorporation of copper leading to Cu x SiBEA induces a reduction of intensity of these bands, suggesting that silanol groups are consumed in the reaction with copper precursor.…”

Vibrational Study on the Local Structure of Post‐Synthesis and Hybrid Mesoporous Materials: Are There Fundamental Distinctions?

“…[17][18][19][20][21] In previous work the discussion focused on the study of the acidity of the hydroxy groups. [18] In particular, the nOH mode region can provide very rich data on "free" and "hydrogen-bonded" silanols, so that information about the nature of OH groups at the surface of the different materials can be inferred.…”

“…[14][15][16] Although several reports have discussed the study of hydroxy groups, [17][18][19][20][21] none of them considered the problem of mesoporous hybrid organic-inorganic materials. Only recently was the study of periodic mesoporous organosilicas (PMOs) by vibrational spectroscopy addressed by Hoffmann and co-workers, [22] who compared experimental data with results of DFT calculations to probe the nSiC modes of several organic building blocks.…”

Periodic Mesoporous Silicas and Organosilicas: An Overview Towards Catalysis

“…Therefore, the Si-O-M bonds in mesoporous materials should be less reactive and have lower redox potential than those in zeolite samples. Further, since a part of active metal sites can be located inside the walls in mesoporous materials, these sites are not accessible for the reactants and this property was commonly observed when the metal precursor was introduced together with the silica source during the synthesis [28,29]. Another difference with zeolite concerns the nature of framework itself.…”

“…Ozin and co-workers also studied the co-condensation of 1,2-bis(triethoxysilyl)ethylene with TEOS using C 16 TABr under basic reaction conditions. [15] From, TEM, FT-Raman and 13 C and 29 Si CP/MAS NMR analysis they concluded that materials with lower amounts of BTEY had the truly hexagonal structural order [19]. PMOs are unique as compared to the first generation ordered mesoporous silicas as they contain both inorganic and organic groups in their channel walls (smart channels).…”