Mesoporous Benzene−Silica Hybrid Materials with a Different Degree of Order in the Wall Structure:  An IR Comparative Study

Abstract

Recent joint IR and computational work (Onida et al. J. Phys. Chem B 2005) has allowed a detailed characterization of the isolated silanols at the surface of highly ordered benzene-silica hybrid material. In the present paper, a similar characterization is provided for a less ordered sample. The comparison permits the assignment of IR features to the interaction of silanols either with one another or with benzene rings of the structure. The extent of structural imperfections appears to be limited, for example, no more than pairs of interacting silanols are found, readily healed by thermal treatment. Evidence is also provided that probe molecules with simultaneous H-acceptor and H-donor properties (benzene, methylacetylene) may interact with both the acidic proton in silanols and the electronic cloud in the framework aromatic rings.

Fluorescence studies on phenylene moieties embedded in a framework of periodic mesoporous organosilica

“…32 Onida et al carried out FTIR spectroscopy on silanols in crystal-like Ph-PMO and characterized them to be an isolated silanol, mutually hydrogen bonded silanols and a silanol interacting with a benzene ring. 29 In the present studied system of crystal-like Ph-PMO, 16.5% of the Si-O bonds are uncondensed silanol groups; that is, there is one silanol on average for one Ph moiety having six Si-O bonds. Thus, the concentrations of the Ph moieties and the silanols are calculated to be ca.…”

“…The existing structures of silanol species in Ph-PMOs were assigned by means of FT-IR spectroscopy as isolated silanols, silanols engaged in intra-framework hydrogen bonding with phenylene rings and mutually hydrogen bonded silanol pairs. [28][29][30] The fluorescence quantum yields of crystal-like and amorphous Ph-PMOs dispersed in MeOH/EtOH at room temperature are 0.031 and 0.038, respectively. The fluorescence quantum yields of Ph-PMOs are somewhat smaller compared to that of the precursor molecule 1,4-bis(triethoxysilyl)-benzene (BTEB) in 2-propanol (0.07).…”

Highly Ordered Mesoporous Organosilica Hybrid Materials

“…54,55 Morell and co-workers reported the in situ synchrotron SAXS/XRD study to give further insight on the formation of ordered mesoscopic hybrid phenylene-silicas with crystal-like pore walls. 56 Recently, Okamoto et al showed the self-organization of non-porous phenylene-silica hybrid solids with a crystal-like long range-ordered structure.…”

Liquid crystalline phases of linear alkylbenzene sulphonate in spray-dried detergent powders studied by small-angle X-ray scattering, TEM, and ATR-IR spectroscopy

“…This observation was in good agreement with the findings of Boissière, et al [43] who suggested that the symmetric stretching vibration of S-O bonds is not affected by water layer thickness. The isolated silanol groups (Si-OH) have been shown to have a tendency to interact with polarizable objects such as benzene rings via hydrogen bonding [44]. Evanson…”