Rapid catalytic reduction of environmentally toxic azo dye pollutant by Prussian blue analogue nanocatalyst

The release of toxic azo dyes pollutants in the environment from different industries represents a public health concern and a serious environmental problem. Therefore, the conversion of hazardous methyl orange (MO) azo dye to environmentally benign products is a critical demand. In this work, an eco-friendly Prussian blue analogue (PBA) was synthesized and its catalytic activity toward the reduction of MO was investigated. The PBA copper(ii) hexacyanocobaltate(III) (Cu3[Co(CN)6]2) was synthesized by a facile inexpensive chemical coprecipitation method without using hazardous solvents. The nanocatalyst was characterized using XPS, Raman, FTIR spectroscopy, and XRD. The chemical reduction of MO using NaBH4 and the PBA as nanocatalyst was monitored by UV-VIS spectroscopy. Toxic MO was completely reduced in 105 s with a rate constant (k) 0.0386 s-1 using only 10 μg of the PBA nanocatalyst. Besides the powerful catalytic activity, the nanocatalyst also showed excellent stability and recyclability for ten consecutive cycles, with no significant decrease in the catalytic performance. Therefore, the proposed PBA is a promising, stable, cost-effective, and eco-friendly nanocatalyst for the rapid elimination of hazardous azo dyes.

The proton conduction behavior of two 1D open-framework metal phosphates with similar crystal structures and different hydrogen bond networks

Two open-framework zinc phosphates [C₃N₂H₁₂][Zn(HPO₄)₂] (1) and [C₆N₄H₂₂]_0.5[Zn(HPO₄)₂] (2) were synthesized via hydrothermal reaction and characterized by powder X-ray diffraction, thermogravimetric analysis and scanning electron microscopy. Both compounds have a similar crystal structure and macroscopic morphology. However, the difference in equilibrium cations, in which the propylene diamine is for 1 and the triethylenetetramine is for 2, results in a significant distinction in the dense hydrogen grid. The diprotonated propylene diamine molecule in 1 is more favorable for forming a hydrogen-bond network in three dimensions than in 2, in which the twisted triethylenetetramine forms a hydrogen bond grid with the inorganic framework only in two dimensions owing to its large steric effect. This distinction further leads to a disparity in the proton conductivity of both compounds. The proton conductivity of 1 can reach 1.00 × 10^-3 S cm^-1 under ambient conditions (303 K and 75% RH) and then increase to 1.11 × 10^-2 S cm^-1 at 333 K and 99% RH, which is the highest value among the open-framework metal phosphate proton conductors operated in the same conduction. In contrast, the proton conductivity of 2 is four orders of magnitude smaller than 1 at 303 K and 75% RH and two orders smaller than 1 at 333 K and 99% RH.

Hydrogels with both mechanical strength and luminescence anisotropy

How to produce luminescent materials with anisotropic emission properties in a universal manner remains an open issue. We here report a range of hydrogels with both anisotropic mechanical strength and...

Efficiently Boosting Moisture Retention Capacity of Porous Superprotonic Conducting MOF-802 at Ambient Humidity via Forming a Hydrogel Composite Strategy

Metal-organic frameworks (MOFs) provided a versatile platform for the development of new solid protonic electrolytes but faced great challenges regarding their low chemical stability and poor moisture retention capacity. Herein, we presented the proton-conducting study for zirconium-based MOF-802, revealing that MOF-802 possessed excellent features of extra aqueous and acidic stabilities and room-temperature superprotonic conduction with a proton conductivity of 1.05 × 10^-2 S cm^-1 at 288 K under 98% relative humidity (RH). Unfortunately, due to the liberation of water molecules from pores/channels, the proton conductivity of MOF-802 dropped significantly at the temperature above 318 K. To solve this issue, for the first time, MOF-802 was hybridized with poly(vinyl alcohol) (PVA) to form MOF-802@PVA hydrogel composites, where the moisture retention capacity of MOF-802 was greatly improved, giving the high room-temperature proton conductivity over 10^-3 S cm^-1 under ambient humidity. This work paves a new way to improve the moisture retention capacity and proton-conducting performances of porous proton conductors.