Metal-organic frameworks MIL-88A hexagonal microrods as a new photocatalyst for efficient decolorization of methylene blue dye.

Metal-organic frameworks (MOFs) MIL-88A hexagonal microrods as a new photocatalyst show an active performance for methylene blue (MB) dye decolorization using visible light. MB decolorization over the MIL-88A photocatalyst follows first-order kinetics. The addition of a H2O2 electron acceptor can markedly enhance the photocatalytic MB decoloration performance of MIL-88A. Moreover, MIL-88A showed a very stable activity for MB decoloration after four consecutive usages. Owing to the advantages of the visible light response, low cost and abundance in nature, this active MIL-88A MOF photocatalyst would have great potential for environmental purification.

Thiol-functionalization of metal-organic framework by a facile coordination-based postsynthetic strategy and enhanced removal of Hg2+ from water.

The presence of coordinatively unsaturated metal centers in metal-organic frameworks (MOFs) provides an accessible way to selectively functionalize MOFs through coordination bonds. In this work, we describe thiol-functionalization of MOFs by choosing a well known three-dimensional (3D) Cu-based MOF, i.e. [Cu(3)(BTC)(2)(H(2)O)(3)](n) (HKUST-1, BTC=benzene-1,3,5-tricarboxylate), by a facile coordination-based postsynthetic strategy, and demonstrate their application for removal of heavy metal ion from water. A series of [Cu(3)(BTC)(2)](n) samples stoichiometrically decorated with thiol groups has been prepared through coordination bonding of coordinatively unsaturated metal centers in HKUST-1 with -SH group in dithioglycol. The obtained thiol-functionalized samples were characterized by powder X-ray diffraction, scanning electron microscope, energy dispersive X-ray spectroscopy, infrared spectroscopy, and N(2) sorption-desorption isothermal. Significantly, the thiol-functionalized [Cu(3)(BTC)(2)](n) exhibited remarkably high adsorption affinity (K(d)=4.73 × 10(5)mL g(-1)) and high adsorption capacity (714.29 mg g(-1)) for Hg(2+) adsorption from water, while the unfunctionalized HKUST-1 showed no adsorption of Hg(2+) under the same condition.

New photocatalysts based on MIL-53 metal-organic frameworks for the decolorization of methylene blue dye.

The photocatalytic decolorization of methylene blue dye in aqueous solution using a novel photocatalyst MIL-53(Fe) metal-organic frameworks was investigated under UV-vis light and visible light irradiation. The effect of electron acceptor H(2)O(2), KBrO(3) and (NH(4))(2)S(2)O(8) addition on the photocatalytic performance of MIL-53(Fe) was also evaluated. The results show that MIL-53(Fe) photocatalyst exhibited photocatalytic activity for MB decolorization both under UV-vis light and visible light irradiation, and the MB decolorization over MIL-53(Fe) photocatalyst followed the first-order kinetics. The addition of different electron acceptors all enhances the photocatalytic performance of MIL-53(Fe) photocatalyst, and the enhanced rate follows the order of H(2)O(2)>(NH(4))(2)S(2)O(8)>KBrO(3) under UV-vis light irradiation, while in the order of (NH(4))(2)S(2)O(8)>H(2)O(2)>KBrO(3) under visible light irradiation. Moreover, MIL-53(Fe) did not exhibit any obvious loss of the activity for MB decolorization during five repeated usages. The photocatalytic activities over MIL-53(M) (M=Al, Fe), the isostructure to MIL-53(Fe), indicate that the metal centers show nil effect on the photocatalytic activity of MIL-53(M) photocatalysts.

Microwave-enhanced synthesis of magnetic porous covalent triazine-based framework composites for fast separation of organic dye from aqueous solution.

A novel type of magnetic porous carbonaceous polymeric material, CTF/Fe(2)O(3) composite (CTF = covalent triazine-based framework), has been synthesized by a facile microwave-enhanced high-temperature ionothermal method. By selecting ZnCl(2) as a reaction medium and the Lewis acid catalyst, and choosing FeCl(3)·6H(2)O as an iron oxide precursor, a series of CTF/Fe(2)O(3) composites with different γ-Fe(2)O(3) contents has been prepared in 60 min. The resulting samples were characterized by the X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibration sample magnetometer (VSM), and N(2) sorption-desorption isotherms. The obtained CTF/Fe(2)O(3) composites exhibit high surface areas (930-1149 m(2) g(-1)), and their saturation magnetizations at 300 K vary from 1.1 to 5.9 emu g(-1), depending respectively on different Fe(2)O(3) contents (6.43-12.43 wt%) in the CTF/Fe(2)O(3) composites. The CTF/Fe(2)O(3) composites were applied to remove organic dye from aqueous solution by selecting methyl orange as a model molecule, and both high adsorption capacity (291 mg g(-1), corresponding to 0.889 mmol g(-1)) and fast adsorption kinetics (k(ads) = 4.31 m(2) mg(-1) min(-1)) were observed.

[The effect of spectral range on the measurement of ozone in the atmosphere by DOAS].

Ozone (O3) often serves as the benchmark for the overall pollution level of a given airshed and it is critical that the measurement technique be accurate and precise, In the DOAS measurement, the accuracy of O3 concentration is determined by the selected spectral range. The present paper focuses on the effect of spectral range on the detected characteristic absorption structure of O3, and the variation of differential cross section of O3 with the change in spectral range and the source of interference in different spectral range. The effect of practical atmospheric light extinction on the light intensities of different spectral ranges was deduced; the effect of spectral range on the accuracy was determined by detecting the standard gases at different concentration and different spectral resolution. The optimized spectral range was determined for O3, which can yield high sensitivity, good selectivity and a reasonable time resolution for the accurate qualitative and quantitative analysis of O3.

[Monitoring and analysis of air pollutants using DOAS in winter of Beijing].

Based on the differential optical absorption spectroscopy (DOAS) technology, the measurement of air pollutants (SOz, NO2, HONO and HCHO) was performed continuously from Jan 19, 2007 to Feb 8, 2007 in Peking University campus. The typical diurnal variation characteristic of SO2 concentration, the main source and the meteorological factors that influence the pollutants were analyzed. The results indicated that the typical diurnal variation of SO2 concentration has the same shape as the letter "V" when wind speed was low, and in the afternoon the SO2 concentration was the lowest, while in other time it was high. Coal-burning made prominent contribution to the concentration of atmospheric various pollutants in the heating period of Beijing. Wind speed played a leading role and other meteorological factors also have some effect, which resulted from the influence of the meteorology on diffusion, transmission, elimination of air pollutants.

[Ring effect and correction studies while retrieving trace gas concentration with passive DOAS].

The method of retrieving the concentration of trace gases using of the diagnostic absorption of trace gases based on the scattered sunlight is called passive DOAS. It has been developed so fast in recent years because it remains simple and is prone to being combined with different platform. While retrieving the column density of trace gases with the scattered sunlight as light source, it will be affected strongly by solar Fraunhofer lines, which is also called Ring effect. It makes it hard to retrieve trace gases concentration and affects measurement precision, especially for lower concentration. The influence of Ring effect and its relation with solar zenith angle in stable day will be introduced in the present paper, and the modification will be provided so that different Ring spectrum is selected according to different solar zenith angle. The slant column density (SCD) of NO2 for 3 stable days was retrieved with this modification. It was proved that the modification is possible.

[Measurement and retrieval of indicators for fast VOCs atmospheric photochemistry with differential optical absorption spectroscopy].

Featuring excellent response characteristics and detection sensitivity and with much lower operational cost, differential optical absorption spectroscopy (DOAS) can be a powerful tool to trace concentration variation of trace indicators -O3, Ox (O3 + NO2) and HCHO for fast VOCs atmospheric photochemistry. But it's difficult to measure those gases accurately because of trace concentration. Here using a self-made DOAS system, the accurate measurement of those indicators was achieved through improving the ratio of signal to noise ratio and correcting the background scattering light; the retrieving method of those indicators was developed through eliminating the temperature effect of absorption cross section, accurately removing the intrinsic structure and lamp structure of spectrum. The preference of different spectral windows that could be used for the concentration retrieval of those indicators was analyzed and compared including interfering factors, results retrieved and the accuracy.

[The effect of resolution on the measurement of carbon bisulfide by DOAS].

Featuring excellent response characteristics and detection sensitivity and with much lower operational cost, differential optical absorption spectroscopy (DOAS) can be a powerful tool to trace the concentration variation of carbon bisulfide (CS2), a kind of poisonous gas with bad smell. In the DOAS measurement, the accuracy of the carbon bisulfide results is determined by the selected spectral resolution. The present paper focuses on the effect of resolution on the detected characteristic absorption structure of CS2 and the variation in differential cross section of CS2 with the change in resolution, from which the effect of resolution on the detection limit of CS2 is deduced. In the end, the functional dependence of the ratio of signal to noise (S/N) on the resolution is reduced by studying the relationship between light intensity and resolution. And the optimized resolution is determined as 0. 41-0. 50 nm (FWHM) with the lowest S/N. The optimized resolution range can yield high sensitivity, good selectivity and a reasonable time resolution for the accurate qualitative and quantitative analysis of CS2 (the results of five different concentration cells show linear correlation with r = 0.999 9 and all the relative standard deviations are less than 0.3% with n = 10). In the end, the long time, real time and continuous monitoring of CS2 was carried out in the Fengtai District of Beijing, and a good result was obtained.