Topochemical polymerization of diphenyldiacetylene-based materials and the relevant application in photocatalysis

Light-Induced Self-Assembled Polydiacetylene/Carbon Dot Functional "Honeycomb"

The design of functional supramolecular assemblies from individual molecular building blocks is a fundamental challenge in chemistry and material science. We report on the fabrication of "honeycomb" films by light-induced coassembly of diacetylene derivatives and carbon dots. Specifically, modulating noncovalent interactions between the carbon dots, macrocyclic diacetylene, and anthraquinone diacetylene facilitates formation of thin films exhibiting a long-range, uniform pore structure. We show that light irradiation at distinct wavelengths plays a key role in the assembly process and generation of unique macro-porous morphology, by both initiating interactions between the carbon dots and the anthraquinone moieties and giving rise to the topotactic polymerization of the polydiacetylene network. We further demonstrate utilization of the macro-porous film as a photocatalytic platform for water pollutant degradation and as potential supercapacitor electrodes, both applications taking advantage of the high surface area, hydrophobicity, and pore structure of the film.

Steel slags for enhanced removal of landfill leachate in a three-dimensional electrochemical oxidation system

In this study, a three-dimensional electrochemical oxidation system, with steel slags as particle electrodes, was applied to deal with landfill leachate. The characteristics of particle electrodes were investigated by scanning electron microscope (SEM), X-ray fluorescence spectroscopy (XRF) and X-ray diffraction (XRD) measurements. It was found that the steel slag exhibited rough and irregular surface and mainly consisted of SiO2 (Quartz), which indicated the enhanced absorbed and electroconducted abilities. Subsequently, comparative degradation tests between two-dimensional (2D) and three-dimensional (3D) electrochemical oxidation systems were carried out and results indicated removal efficiencies of COD. Moreover, NH4+-N from landfill leachate in 3D system was greatly improved compared with that of 2D system. Besides, operating conditions were also optimized to interelectrode distance of 1 cm, current density of 20 mA·cm-2, initial pH value of 4.4 and steel slag concentration of 0.30 g·mL-1, all of which were determined to guarantee excellent landfill leachate removal efficiency. In addition, a possible removal mechanism for this system was proposed. The introduction of steel slag particle electrodes in three-dimensional electrochemical oxidation system implied the concept for "using waste to treat waste", providing a workable way in pollutant elimination.

Recent Developments in Heterogeneous Photocatalysts with Near-Infrared Response

Photocatalytic technology has been considered as an efficient protocol to drive chemical reactions in a sustainable and green way. With the assistance of semiconductor-based materials, heterogeneous photocatalysis converts solar energy directly into chemical energy that can be readily stored. It has been employed in several fields including CO2 reduction, H2O splitting, and organic synthesis. Given that near-infrared (NIR) light occupies 47% of sunlight, photocatalytic systems with a NIR response are gaining more and more attention. To enhance the solar-to-chemical conversion efficiency, precise regulation of the symmetric/asymmetric nanostructures and band structures of NIR-response photocatalysts is indispensable. Under the irradiation of NIR light, the symmetric nano-morphologies (e.g., rod-like core-shell shape), asymmetric electronic structures (e.g., defect levels in band gap) and asymmetric heterojunctions (e.g., PN junctions, semiconductor-metal or semiconductor-dye composites) of designed photocatalytic systems play key roles in promoting the light absorption, the separation of electron/hole pairs, the transport of charge carriers to the surface, or the rate of surface photocatalytic reactions. This review will comprehensively analyze the four main synthesis protocols for the fabrication of NIR-response photocatalysts with improved reaction performance. The design methods involve bandgap engineering for the direct utilization of NIR photoenergy, the up-conversion of NIR light into ultraviolet/visible light, and the photothermal effect by converting NIR photons into local heat. Additionally, challenges and perspectives for the further development of heterogeneous photocatalysts with NIR response are also discussed based on their potential applications.

Hydrogen-bond-driven supramolecular self-assembly of diacetylene derivatives for topochemical polymerization in solution

We report here photoinduced topochemical polymerizations of diacetylene-derivatized compound by the introduction of amide functions as the structure directing agent in solution.