Design, Synthesis, Characterization And Performance Of Catalytic And Luminescent Inorganic-organic Mesoporous Materials

Both inorganic and organic materials have their own properties playing great roles in material science. Inorganic materials have attracted considerable attentions of researchers owing to their high intensity, high rigidity, high hydrothermal and thermal stability. Solid catalysts can provide numerous opportunities for recovering and recycling catalysts from reaction environments, while they also suffer from their inability. Since much is known about organic materials, the immobilization of these entities onto solids to create organic-inorganic hybrid catalysts can be accomplished in some aspects of design. Organic groups can be incorporated into the mesoporous materials through grafting or co-condensation methods. And, The goal is to utilize the organic moiety as the active sites or further to introduce new active sites. The resulting inorganic-organic materials preserve the characteristic structural organization of mesoporous silica, but the introduced organic groups make them unique materials for applications such as heterogenization of the homogeneous catalysts, adsorbents and optoelectronic devices. In this thesis, we focused on the design, preparation and related application study of inorganic-organic hybrid mesoporous materials with different components and different mesostructures, researching their capability, interfacial characters and conversion of functional groups. First, the organic groups of amino and amine have been introduced into the pores or within the frameworks of mesoporous materials through grafting or co-condensation methods. The obtained materials were used as base catalysts. Then, some organic groups, such as benzyl, anthracene groups and 8-hydroxyquinoline complexes, have been successfully introduced into the pores of amino-functionalized mesoporous materials. The obtained hybrids have greatly promising applications in base catalysis (Claisen-Schmidt condensation reaction) and selective oxidation reactions ( phenol hydroxylation reaction ).Flavanone is an important polyphenolic substance, which is widely used in numerous pharmacological applications for antimalarial, anticancer, anti-inflam-matory, cytotoxic, antibacterial, and anti-AIDS. Flavanone is usually synthesized via the Claisen-Schmidt condensation between benzaldehyde with 2′-hydroxyacetopheone and the subsequent isomerization of 2′-hydroxychalcone intermediates under homogeneous basic or acidic conditions. The organic groups of amino and amine can catalyse reaction as base sites. In the chapter two, A hybrid mesoporous HMS silica materials have been synthesized by co-condensation from tetraethylorthosilicate (TEOS) and bis[3-(trimethoxysilyl) propyl]amine (BTMSPA) using octadecylamine as template via the"S0 I0"route. The sequential addition of TEOS and BTMSPA resulted in well-ordered porous hybrid silicates, which can be characterized by means of X-ray diffraction, N2 gas sorption experiments. 29Si MAS NMR, elemental analysis, FT-IR and condensation reaction of benzaldehyde with 2′-hydroxyacetopheone indicated that the amine groups have been introduced. By adjusting the amount of BTMSPA, the amount of amine introduced can be changed. In addition, it is found that the higher amount of amine groups can be introduced, the more 2′-hydroxyacetopheone can be transformed and the higher flavanone selectivity can be obtained. But, if the amount is too large to be not within the frameworks as base sites, the conversion of 2′-hydroxyacetopheone gradually decreases.SBA-15 mesoporous silica has been functionalized with aminopropyl groups through a simple co-condensation approach reported by Soofin Cheng group. The material was found to be an efficient base catalyst in reactions of benzaldehyde and 2′-hydroxyacetophenone to flavanone. In the chapter three, aminopropyl-functionalized SBA-15 (APS-SBA-15) materials are prepared by postgrafting method. APS-SBA-15 catalysts display high activities for the synthesis of flavanone. Then, benzyl groups and anthracene groups have been successfully introduced in the pores of APS-SBA-15. The obtained mesoporous solid base catalysts ( Benzyl-APS-SBA-15 and Anthracene-APS-SBA-15 ) also been applied to the catalytic preparation of flavanone. They display higher activities and higher flavanone selectivity than APS-SBA-15. Additionally, we also investigated the effect of introducing benzyl groups and anthracene groups on their catalytic performance. The size of organic functional groups have a great effect on the distribution of products .It is found that the larger organic groups introduced is, the less selectivity the product of further Claisen-Schmidt condensation reaction of flavanone with benzaldehyde can be obtained.Hydroxylation of phenol to diphenols is an important selective oxidation reaction, whose products such as catechol and hydroquinone are used in such diverse applications as photographic chemicals, antioxidants, flavoring agents, polymerization inhibitors and pharmaceuticals. Phenol hydroxylation with H2O2 as the oxidant has become one of the promising approaches in the 21st century because it demands on simple techniques and produces less environmental pollution. In the chapter four, Mesoporous SBA-15 grafted by 3-aminopropyl groups (denoted as APS-SBA-15) reacted with 5-formyl-8-hydroxyquinoline to anchor 8-quinolinol ligand on the silica. Iron(Ⅱ) and Cu (Ⅱ) cations were then introduced into pore channels by coordination with N and O sites of 8-quinolinol. The obtained Iron(Ⅱ)-8-quinolinol functionalized SBA-15 materials (named as Fe (Ⅱ)-Q-APS-SBA-15) and Copper (Ⅱ)-8-quinolinol functionalized SBA-15 materials (named as Cu (Ⅱ)-Q-APS-SBA-15) were tested as catalysts for phenol hydroxylation using H2O2 (30%) as oxidant. They display excellently catalytic performance with high conversion of phenol and high selectivity to diphenol. Additionally, in the hydroxylation reaction of phenol with H2O2, high phenol conversion of 42.9% with the selectivity to diphenol (catechol (CAT) and hydroquinone (HQ) of 98.1% can be obtained at room temperature over Iron (Ⅱ)-Q-APS-SBA-15. Additionally, this characteristic has not been observed over other catalysts by far, which makes Iron (Ⅱ)-Q-APS-SBA-15 an excellent catalyst for phenol hydroxylation.Aluminum tri(8-hydroxyquinoline) is one of the most stable fluorescent solid-state materials, making it the emission and electron-transport layer of choice in organic light-emitting diodes (OLEDS). In recent years, enhancement of electroluminescent (EL) efficiency and color tuning through molecular doping or microcavity-assisted color tuning has increased the range of applications. This paper presents the first report of photoluminescence and relevant features of 8-hydroxyquinoline aluminum (Alq3) introduced into the pores of APS-SBA-15 as monomers. Considering the nanometer pore size of SBA-15, since Alq3 molecules could be highly dispersed in the pores of SBA-15, the aggregation of Alq3 molecules is difficult in the nanosized holes, and so the Alq3 is present as monomers, resulting in blue shift of emission and absorption spectra. This hybrid electroluminescent solid material displays an obvious blue-shifted photo-luminescence(PL) and high EL efficiency, and hence has greatly promising applications in novel optoelectronic devices, such as microcavity, flat panel display and quantum devices. Another inorganic-organic photoluminescence solid material was obtained by immobilizing N-benzylcarbazole compound to the amino-functionalized mesoporous SBA-15 silica, and designated as N-benzylcarbazole-amino-SBA-15 (BCz-amino-SBA-15). The absorbance and emission studies revealed that the fluorescent N-BCz-amino-SBA-15 nanomaterial exhibited red-shift character in comparison with pure N-benzylcarbazole. The red-shifts of absorption and emission spectra can be interpreted as follows: when N-benzylcarbazole molecules are incorporated into the channels of SBA-15, the interactions of N-benzylcarbazole molecules and APS-SBA-15 could increase in the nanosized holes of APS-SBA-15 because more N-benzylcarbazole can be grafted in relative large pore of SBA-15..Above all, by the incorporation of organic guest molecules into the channels of functionalized mesoporous silica, organic-inorganic hybrid solid materials have been developed. We are confident that new surprises in materials performance and properties will emerge and that the excitement of the field will continue in the upcoming years.