The present work reports Förster resonance energy transfer (FRET) from 1,8-naphthalimide (NI) donors bound to the pore walls of mesoporous silicas to perylenediimide (PDI) acceptors doped into the mesochannels. Mesoporous organosilicas containing covalently bound NI were synthesized by co-condensation of tetraethylorthosilicate (TEOS) with N-(3-(triethoxysilyl)­propyl)-1,8-naphthalimide (TEPNI) in the presence of a block copolymer surfactant as a template. The resulting materials were highly ordered, presenting a 2D hexagonal structure, and displayed easily tunable optical properties, which could be controlled by the amount of NI in the sample. A sample prepared from a diluted TEPNI solution (SBANId) presented a blue, monomerlike emission. In contrast, when a concentrated TEPNI solution was used, the resulting material (SBANIc) displayed a green, excimerlike emission. For the FRET studies, N,N′-bis­(2,6-dimethylphenyl)-3,4,9,10-perylenediimide was doped into the pores of the SBANI samples from chloroform solutions. When excited at the NI absorption maximum (350 nm), PDI-doped SBANIc showed intense quenching of the NI emission band, even at very low PDI doping, with quenching efficiencies reaching nearly 80% with only 0.6 mol % PDI (PDI/NI ≈ 1:170). The emission of PDI was observed at higher doping ratios, even though the PDI hardly absorbs at 350 nm, thus evidencing FRET from the host NI to the guest PDI. SBANI materials with a suitable amount of the PDI dopant displayed a white emission, spanning the whole visible spectrum.

Mesoporous gamma-aluminas (γ-Al 2 O 3 ) were synthesized starting from an unusual precursor of polyoxohydroxide aluminum (POHA). This precursor was obtained from aluminum oxidation in alkaline water-ethanol solvent in the presence of d-glucose that induces the formation of a gel, which leads to the POAH powder after ethanolic treatment. Precipitated POHAs were calcined at different temperatures (300, 400, 700 and 900 °C) resulting in the metastable γ-Al 2 O 3 phase. Whereas at 300 °C no γ-Al 2 O 3 phase was formed, unexpectedly, mesoporous γ-Al 2 O 3 was obtained at 400 ºC having a high specific surface area (282 m 2 /g) and a narrow pore size distribution. At higher temperatures, the aluminas had the expected decrease in surface area: 166 m 2 /g (700 °C) and 129 m 2 /g (900 °C), respectively. The structural change from POHA to alumina calcined at 400 ºC occurs directly without the need to isolate the hydroxide or oxyhydroxide aluminum precursors. Both POHA and transition aluminas were characterized by Fourier Transform Infrared spectroscopy (FTIR), X-ray diffraction (XRD), N 2 sorption and Scanning Electron Microscopy (SEM). These findings show an alternative route to produce high standard aluminas.

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Novel periodic mesoporous organosilicas (PMOs) containing 1,4,5,8-Naphthalenediimide (NDI) chromophores as an integral part of the pore walls were synthesized in acidic conditions, in the presence of inorganic tetraethyl orthosilicate, using triblock copolymer surfactant Pluronic P-123 as a template. The NDI precursor, the bridged silsesquioxane N, N'-bis(3-triethoxysilylpropyl)-1,4,5,8-naphthalenediimide, was synthesized by reaction of 1,4,5,8-naphthalenetetracarboxylic dianhydride with excess 3-aminopropyltriethoxysilane. A series of samples containing up to 19% (weight %) of NDI were prepared (the materials were labeled PMONDIs). C andSi solid-state nuclear magnetic resonance revealed that the NDI moiety was intact in the PMONDIs and efficiently grafted to the silica network. Samples with up to 16% NDI load presented an ordered two-dimensional-hexagonal mesoscopic structure, according to small-angle X-ray scattering, transmission electron microscopy, and nitrogen adsorption isotherms. Fluorescence spectra of the PMONDIs showed excimer formation upon excitation, suggesting high flexibility of the organic moieties. Reduction of PMONDIs with aqueous sodium dithionite led to the formation of wall-embedded NDI anion radicals, as observed by the appearance of new visible/near-infrared absorption bands. The PMONDIs were also shown to be efficient photocatalysts in the degradation of sulfadiazine, an antibiotic selected here as a model pollutant, which is usually present in water bodies and wastewater.

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