Herein we report the first two (5,5)-connected isomeric frameworks, namely, (Me2NH2)[Zn2L(H2O)]·3.5DMF (1) and (Me2NH2) [Zn2L(H2O)]·6DMF·4H2O (2) (DMF = dimethylformamide, H5L = 5,5′-(6-(4-carboxyphenylamino)-1,3,5-triazine-2,4-diyldiimino) diisophthalic acid), obtained via assembly reactions between Zn2+ and a semi-rigid pentacarboxylate ligand (L5−). Single-crystal X-ray diffraction analyses reveal that both compounds are three dimensional metal–organic frameworks (MOFs) built of the same {Zn2(CO2)5} molecular building blocks (MBBs) and L5− ligands but have different topologies (point symbols of (44·66) and (46·64)(46·64) for 1 and 2, respectively). The mechanisms of the selective and efficient quenching of their photoluminescence (PL) by a series of nitroaromatic (NACs) solutions could be explained by electron transfer, long range energy transfer and/or electrostatic interactions. Remarkably, 1 and 2 can impressively detect the concentrations of dinoseb in solutions down to 0.09 and 0.11 ppm, respectively. Their PL could also be quenched by nitrobenzene (NB) and 4-nitrotoluene (4-NT) vapors, and the emission from 2 can be more quickly quenched than that from 1 possibly due to 2's larger pores and faster uptake of NAC vapors. 1 and 2 demonstrate significantly better performances than the two previously reported 4-connected MOFs using Zn2+ and a ligand isomeric to L5− in detecting NACs in both suspension and vapour mainly due to the ligands' different LUMOs and arrangements of carboxylate groups (L. Di, J. J. Zhang, S. Q. Liu, J. Ni, H. Zhou and Y. J. Sun, Cryst. Growth Des., 2016, 16, 4539). This work sheds light on not only understanding of the formation of framework isomers but also the development of MOF-based NAC probes with better performances via judicious selection of suitable ligands.

•C-TiO2 was facilely prepared by in-situ one-pot hydrothermal synthesis method.•Glucose was employed as the carbon source.•C-TiO2 exhibited visible light activity towards RhB and MB degradation.•The composite photocatalyst has excellent reproducibility.A simple and convenient in-situ one-pot hydrothermal synthesis method was developed for preparing crystalline carbon modified titanium dioxide composite (C-TiO2) by using tetrabutyle titanate and glucose as co-precursors. Such a method can avoid the expensive templates and tedious procedures for the fabrication of carbon doped titanium dioxide materials. The morphology and microstructure characteristics of C-TiO2 photocatalysts were characterized by means of XRD, TEM, FT-IR, N2 adsorption-desorption measurements, elemental analysis, XPS and UV-vis/DRS. The experimental results showed that the TiO2 nanoparticles were dispersed unanimously on carbon layer. The as prepared C-TiO2 composites possessed larger specific surface area, higher separation efficiency of charge carrier pairs and greater visible light absorbance than pure TiO2. The fabricated C-TiO2 samples showed excellent photocatalytic activities towards organic dye pollutants (Rhodamine B and methylene blue) under visible light irradiation and the photoactivity of the C-TiO2 samples was superior to pristine TiO2. The enhanced photocatalytic efficiency can be attributed to the synergetic effects of carbon species and TiO2 nanocrystals.Download high-res image (163KB)Download full-size image

•SiO2 aerogel from fly ash supported Fe3O4@TiO2 catalyst was successfully prepared.•The catalyst was facilely prepared by combining sol–gel and hydrothermal method.•The catalyst exhibited high photocatalytic activity and good magnetic properties.•The composite photocatalyst is easily recovered with excellent reproducibility.•The factors affecting photocatalytic activity are analyzed.In this work, a ternary magnetic composite of Fe3O4@TiO2/SiO2 aerogel with good photocatalytic activity was prepared successfully by combining sol–gel and simple hydrothermal methods with Fe3O4@TiO2 core–shell microspheres and SiO2 aerogels from industrial fly ash as starting materials. The structural and magnetic features of the as-obtained Fe3O4@TiO2/SiO2 aerogel composite were investigated by powder X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), transmission electron microscopy (TEM), N2 adsorption–desorption measurements, UV–vis diffuse reflectance spectra (UV–vis/DRS) and vibrating sample magnetometry (VSM). The results showed that Fe3O4@TiO2 core–shell microspheres were dispersed on the surface of SiO2 aerogels. The Fe3O4@TiO2/SiO2 aerogel composite material possessed excellent magnetic properties at room temperature, high adsorption capacity to organic pollutants, enhanced charge separation efficiency and strong light absorption in the visible region. The photocatalytic activity of the prepared Fe3O4@TiO2/SiO2 aerogel for Rhodamine B degradation under visible light irradiation was systematically investigated by varying the operational parameters such as pH value, catalyst concentration, irradiation time, and initial substrate concentration, etc. The photocatalytic reactions obeyed pseudo-first-order kinetics according to Langmuir–Hinshelwood model. The repeatability of photocatalytic activity was also tested. Compared to pure TiO2 and Fe3O4@TiO2 core–shell microspheres, the ternary composite of Fe3O4@TiO2/SiO2 aerogel showed higher photocatalytic activity for Rhodamine B degradation, which meant that this material can serve as an efficient and recyclable multifunctional photocatalyst for the degradation of hazardous organic dyes in wastewater.

In this work, TiO2–Fe3O4/grapheme (RGO) composites with good magnetism and photocatalytic activity were prepared by a facile hydrothermal method with RGO and magnetic TiO2 as starting materials in ethanol–water solvent. The structural and magnetic features of the prepared composite photocatalysts were investigated by powder X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), transmission electron microscopy (TEM), thermogravimetric and differential thermogravimetry analysis (TG-DTG), UV–vis diffuse reflectance spectra (UV–vis/DRS) and vibrating sample magnetometry (VSM). The results showed that the TiO2 coated Fe3O4 nanoparticles with a strong response to external magnetic fields were dispersed uniformly on the surface of RGO nanosheets. The composite catalysts can cause an obvious red shift of UV–vis spectra compared with pure TiO2. The adsorption and photocatalytic activity of the composite catalysts were evaluated by choosing methylene blue (MB) as organic pollutants. The photocatalytic degradation of MB by TiO2–Fe3O4/RGO composites under visible light irradiation was examined by varying the operational parameters such as catalyst amount, irradiation time, pH and initial MB concentration. The photocatalytic reactions obeyed pseudo-first-order kinetics according to Langmuir–Hinshelwood model. The repeatability of photocatalytic activity was also tested. A plausible mechanism was proposed and discussed on the basis of experimental results.

Experiments were conducted to investigate the degradation of 2,6-dinitro-p-cresol (DNPC) in the chlorine dioxide (ClO2) catalytic oxidation process. Pure aluminum oxide was used as the catalyst in this process. The degradation of DNPC by ClO2 using aluminum oxide as catalyst was systematically studied by varying the experimental parameters, such as pH values, catalyst dosage, the initial concentration of DNPC and ClO2, reaction time, etc. Under optimal condition (DNPC concentration 39mg·L−1, ClO2 concentration 0.234 g·L−1, reaction time 15 min, catalyst dosage 4.7 g·L−1 and pH 4.32), almost complete degradation of DNPC can be achieved. The kinetic studies revealed that the ClO2 catalytic oxidation degradation of DNPC followed pseudo-first-order kinetics with respect to both ClO2 and DNPC concentration. The repetitive use of the catalyst was investigated along sequential feed-batch trials. The catalyst performed efficiently after five runs. In addition, a simple and convenient method for the determination of ClO2 in water was developed by using acid chrome black 7 (MB 7) spectrophotometry in this paper.

•We provide a facile one step synthesis of hydrophilic PAA-Ti/TiO2 nanocomposite.•This novel nanocomposite possesses remarkable selectivity for phosphopeptides.•Abundant titanium is available for selective enrichment of phosphopeptides.•Plenty of carboxylate groups are present to inhibit nonspecific absorption.Highly selective enrichment of trace phosphorylated proteins or peptides from complex biological samples is of profound significance for the discovery of disease biomarkers in biological systems. In this study, a novel affinity material has been synthesized to improve the enrichment specificity for phosphopeptides by using PAAS as coupling molecule. In the resulting materials, highly abundant titanium is available for selective enrichment of phosphopeptides, with plenty of carboxylate groups that can inhibit nonspecific adsorption. The enrichment results demonstrated that the hydrophilic PAA-Ti/TiO2 composite possesses excellent selectivity for phosphopeptides even at a very low molar ratio of phosphopeptides/non-phosphopeptides (1:1000), extreme sensitivity (the detection limit was at the fmol level), and high recovery of phosphopeptides (as high as 78%). Moreover, the as-prepared nanocomposite provides effective enrichment of phosphopeptides from real samples (mouse liver), showing great potential in the detection of low-abundance phosphopeptides in biological samples.