Various aromatic-bridged periodic mesoporous organosilica (PMO) thin films were prepared from 100% organosilane precursors containing bridging organics of 1,4-phenylene (Ph), 4,4′-biphenylylene (Bp), 2,6-naphthylene (Nph), and 9,10-anthrylene (Ant) by an evaporation-induced self-assembly approach. Structural and optical properties of the films were characterized. Transparent films with periodic mesostructures were successfully obtained for all the compositions. The absorption spectra of the PMO films were similar to those of their precursors, indicating little interaction between the aromatic groups in the frameworks in the ground state, whereas the fluorescence spectra of the PMO films significantly red-shifted and also broadened compared with those of their precursors, suggesting excimer formation in the excited state. The quantum yields of the Ph-, Nph-, and Ant-PMO films were lower than those of their precursors by solid-state quenching. Exceptionally, the quantum yield increased above that of the precursor for the Bp-PMO film in spite of excimer formation. The high absorption coefficient (87 000 cm -1 ) and high quantum yield (0.45) of the Bp-PMO film indicate its great potential for use as fluorescent materials. IntorductionPeriodic mesoporous organosilicas (PMOs), synthesized from 100% or less organic-bridged organosilane precursors [(R′O) 3 Si-R-Si(OR′) 3 ], are a new class of materials having well-defined nanoporous structure and framework functionalities attributed to organic groups in their pore walls. 1 PMOs have attracted much attention owing to their potential use in various applications such as catalysts, 2 adsorbents, 3 and optical devices. 4 PMOs are particularly suitable for optical applications in which a large amount of organic chromophores can be incorporated within their pore walls. PMOs containing a large amount of chromophores are expected to show a high absorption efficiency of light and unique optical properties due to the densely packed chromophores in their framework. Although several PMOs containing framework organic chromophores, such as viologen, 5 bispyridylethylene, 6 triphenylpyrylium, 7 Ru and Eu complexes, 4 and azobenzene 8 moieties, have been reported so far, these were prepared by co-condensation with a large amount of a pure silica precursor, such as tetraethoxysilane (82-99 mol %). The co-condensation approach resulted in dilution of the organic chromophores in the framework with silica. PMOs prepared from 100% bridged organosilane precursors have been reported for organic chromophores, such as phenylene, 9 biphenylylene, 10 thiophene, 11 diacetylene, 12 and carbazole. 13 However, optical properties of these PMOs have not been studied in detail.Especially for optical applications, transparent film-shaped PMOs 14,15 are advantageous compared with powder-shaped PMOs because of easy shaping (patterning) and low optical loss (no light scattering). Here, we focus on transparent filmshaped PMOs and synthesized PMO films from 100% organosilane precursors containing bridging organ...

Inspired by homogeneous borane catalysts that promote Si-H bond activation, we herein describe an innovative method for surface modification of silica using hydrosilanes as the modification precursor and tris(pentafluorophenyl)borane (B(C6F5)3) as the catalyst. Since the surface modification reaction between surface silanol and hydrosilane is dehydrogenative, progress and termination of the reaction can easily be confirmed by the naked eye. This new metal-free process can be performed at room temperature and requires less than 5 min to complete. Hydrosilanes bearing a range of functional groups, including alcohols and carboxylic acids, have been immobilized by this method. An excellent preservation of delicate functional groups, which are otherwise decomposed in other methods, makes this methodology appealing for versatile applications.

Treatment of an (allyl)organosilane with silica gel in refluxing toluene brought about deallylation forming an Si-O-Si bond with the silicon on the silica gel. This Si-O-Si bond formation provides us with a new reliable method for the functionalization of a silica gel surface.

We report that 2,6-naphthylene-bridged periodic mesoporous organosilicas exhibit unique fluorescence behavior that reflects molecular-scale periodicities in the framework. Periodic mesoporous organosilicas consisting of naphthalene-silica hybrid frameworks were synthesized by hydrolysis and condensation of a naphthalene-derived organosilane precursor in the presence of a template surfactant. The morphologies and meso- and molecular-scale periodicities of the organosilica materials strongly depend on the synthetic conditions. The naphthalene moieties embedded within the molecularly ordered framework exhibited a monomer-band emission, whereas those embedded within the amorphous framework showed a broad emission attributed to an excimer band. These results suggest that the naphthalene moieties fixed within the crystal-like framework are isolated in spite of their densely packed structure, different from conventional organosilica frameworks in which only excimer emission was observed for both the crystal-like and amorphous frameworks at room temperature. This key finding suggests a potential to control interactions between organic groups and thus the optical properties of inorganic/organic hybrids.