Search

This study investigates the photocatalytic reduction of nitroaromatic compounds upon visible light over novel Ce-doped UiO-66/graphene nanocomposites. Ce doped UiO-66 nanostructures and the corresponding graphene hybridized nanocomposites were facilely synthesized by means of one step solvothermal reaction. It has been demonstrated that produced nanocomposites could be used as highly efficient and chemical stable photocatalysts for the reduction of nitroaromatic compounds under visible irradiation and ambient conditions. Compared with the bare UiO-66, Ce-UiO-66/GR distinctly enhanced photocatalytic activity. Ce as “mediator” introduced into the MOFs materials can greatly improve the electron transfer across the interface between grephene and the UiO-66 and further improve the visible light driven photoactivity. This is an effective strategy for the development of high photocatalytic activity MOFs based materials.

Metal-organic frameworks (MOFs), a new class of porous crystalline materials, have attracted great interest as fascinating applications for eco-friendly photocatalysts. In this study, new hybrid MOFs, iron doped zirconium based metal-organic frameworks, FeUiO-66, were successfully synthesized by hydrothermal method firstly. Then the PANI/FeUiO-66 nanohybrids were fabricated through annealing process. The photocatalytic performances of the obtained PANI/FeUiO-66 nanohybrids were evaluated by selectively oxidation of various alcohol substrates using molecular oxygen as a benign oxidant. Boosting by synergistically multi-doped effect, the catalytic activity of the novel PANI/FeUiO-66 is remarkably higher than that of bare UiO-66 under visible light irradiation at ambient temperature. Further analyses revealed that the enhancement of photocatalytic activity originated from the two aspects. On one hand, when the Fe doped into the framework, valence fluctuation of Fe 2+ /Fe 3+ could reduce the recombination rate of photoexcited carriers. On the other hand, based on energy band matching between FeUiO-66 and PANI, the easily formed heterostructures from PANI and FeUiO-66 can efficiently enhance the separation of photogenerated carriers. Furthermore, by virtue of unique advantage of the position of the CB and VB of FeUiO-66, alcohols could be selectively oxidized by the O 2 − and h + . Remarkably, it is expected that the MOF-conductive conjugated polymers nanohybrids could be used as efficient visible light driven photocatalysts for organic transformation with high selectivity under eco-friendly conditions.

Photocatalytic synthesis using visible light is a desirable chemical process because of its potential to utilize sunlight. A heterostructured MIL-125/Ag/g-C3N4 nanocomposite was implemented as an efficient bifunctional visible-light response catalyst for the photoreduction of nitrocompounds and the oxidation of alcohols. The photocatalyst was prepared via an accessible method and characterized by XRD, SEM, TEM, XPS, FT-IR, N2 adsorption–desorption isotherm, UV–vis DRS, PL and EIS. The reactive efficiency of the photocatalyst depends on two primary factors, one is the light adsorption of catalysts, Ag nanoparticles (NPs) were photodeposited on the surface of g-C3N4 and MIL-125 to increase visible-light absorption via the surface plasmon resonance. And the other is the separation efficiency of the photogenerated charge carrier. As an electron-conduction bridge in the interface between MIL-125 and g-C3N4, Ag NPs could facilitate the direct migration of photoinduced electrons from g-C3N4 to MIL-125 and retard the recombination of electron-holes. Therefore, the MIL-125/Ag/g-C3N4 sample shows highest photocatalytic activity compared with MIL-125, g-C3N4, MIL-125/Ag and MIL-125/g-C3N4. A corresponding photocatalytic mechanism of these reactions was discussed in detail. Moreover, the photoreduction of nitrocompounds and oxidation of the alcohols with superior conversions and selectivities were obtained, and the catalyst can be recycled four times. It is concluded that MIL-125/Ag/g-C3N4 would be a promising visible light photocatalyst in the field of selective organic transformations.

A series of MIL-53(Fe)-graphene nanocomposite photocatalysts were synthesized by a facile one-pot solvothermal reaction. All materials have been thoroughly characterized by FT-IR, SEM, TEM, PXRD, UV–vis DRS and PL analysis. It was demonstrated that the introducing of graphene on the MIL-53(Fe) would minimize the recombination of photogenerated electron-hole pairs, thus, leading to the enhancement of photocatalytic activity. MIL-53(Fe)-graphene nanocomposite was an efficient catalyst towards the photocatalytic selectively oxidation of alcohols to the corresponding aldehydes or ketones under visible light and ambient conditions. High selectivity of the aldehydes or ketones (99%) were obtained. Meanwhile, the catalyst can be recycled at least four times without loss of catalytic efficiency. A possible photocatalytic reaction mechanism involving a direct photogenerated hole-oxidation process was also investigated in detail by the active species trapping experiments and the related electrochemical analysis.

A novel organic–inorganic hybrid flame retardant of PGS@B–N prepared via the decoration of palygorskite (PGS) by boric acid (B) and dodecylamine (N) was incorporated with an ethylene-vinyl acetate copolymer (EVA) to improve its flame retardance. The structure and morphology of PGS@B–N were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The flame retardance and burning behavior of the EVA/PGS@B–N/EG (expandable graphite) composite were studied through thermogravimetric analysis (TGA), limiting oxygen index (LOI), vertical burning test (UL-94), and cone calorimeter test (CCT). The results of the UL-94 and LOI tests indicated that the flame retardance of EVA/PGS@B–N/EG was better than that of EVA/PGS/EG flame-retardant composites. The data obtained from the CCT illustrated that the peak heat release rate (PHRR) of EVA with the addition of 30 wt% PGS@B–N/EG was reduced by about 25% compared to EVA with equivalent PGS/EG. The heat release rate (HRR), total release rate (THR), smoke production rate (SPR), and mass loss rate (MLR) of the composite were improved significantly. The TGA data showed that the thermal stability of EVA/PGS@B–N/EG was also well improved at high temperatures. SEM images of cryogenically fractured surfaces illustrated that EVA/PGS@B–N/EG had better interfacial interaction compared with that of EVA/PGS/EG.

Multi-walled carbon nanotubes (MWCNTs) supported HSiW/MWCNTs was successfully prepared and characterized by Fourier transform infrared spectoscopy, X-ray powder diffraction, transmission electron microscopy and N2 adsorption–desorption test. Its catalytic performance for the catalytic Baeyer–Villiger oxidation of cyclic ketones with 30 % H2O2 as oxidants was investigated. It was found that HSiW/MWCNTs was very efficient to transform of some cycloketones to the corresponding lactones with high conversions as well as selectivities. Factors affecting the oxidations and the reusability of the catalyst were also investigated. It was found that the catalyst can be reused seven times in the catalytic oxidation reaction of cyclopentanone without obviously catalytic activity losing in the oxidation. A supported solid acid of HSiW/MWCNTs was used as efficient catalyst for the Baeyer–Villiger oxidation of ketones. High cyclopentanone conversion (98 %) and e- valerolactone selectivity (99 %) were obtained. The catalyst can be reused at least seven runs in the oxidation of cyclopentanone.

Natural palygorskite (PG) was employed to prepare cost-effective, reusable supported catalyst of Pd/PG and Ru/PG through wet impregnation method. The catalysts were characterized through AFM, ICP-AES, XPS, XRD, BET, TEM and FTIR. The catalytic properties of the synthesized catalysts were assessed and optimized through oxidation of alcohols with PhIO as oxidant. It showed that the existence of Ru and Pd in the catalysts dramatically enhanced the catalytic activity with a prominent selectivity of far more than 99% compared with the palygorskite.