Silver-assisted reduction of nitroarenes by an Ag-embedded curcumin/melamine-functionalized magnetic nanocatalyst

In the current study, we introduce a hybrid magnetic nanocomposite comprised of curcumin (Cur), iron oxide magnetic nanoparticles (Fe₃O₄ MNPs), melamine linker (Mel), and silver nanoparticles (Ag NPs). Initially, a facile in situ route is administrated for preparing the Fe₃O₄@Cur/Mel-Ag effectual magnetic catalytic system. In addition, the advanced catalytic performance of the nanocomposite to reduce the nitrobenzene (NB) derivatives as hazardous chemical substances were assessed. Nevertheless, a high reaction yield of 98% has been achieved in short reaction times 10 min. Moreover, the Fe₃O₄@Cur/Mel-Ag magnetic nanocomposite was conveniently collected by an external magnet and recycled 5 times without a noticeable diminish in catalytic performance. Therefore, the prepared magnetic nanocomposite is a privileged substance for NB derivatives reduction since it achieved notable catalytic activity.

Highly Efficient and Selective Capture of Pb(II) by New Crosslinked Melamine-Based Polymethyl Methacrylate for Water Treatment

Owing to the recent developments in the polymer’s properties and application, the demands for designing different structure of polymers are greater than ever. Crosslinked polymers (CPs) are a type of porous materials that have a variety of potential applications. Because of simple methods of modification of polymethyl methacrylate (PMMA), the crosslinked PMMA considers the most commonly polymeric adsorbents. A new crosslinked melamine-based polymethyl methacrylate (C-PMMA/Mel) was prepared via a polycondensation reaction between PMMA and melamine used as a crosslinking agent. Different characterization methods were carried out to investigate the molecular structures, thermal stability, and morphology. C-PMMA/Mel was applied for the adsorption behavior toward different metal cations and detected a selective to Pb(II). The evaluation of the new polymers as adsorbent against Pb(II) ion was studied using the contact time, adsorbent dose, initial concentration, and effects of pH. The adsorption efficiency of heavy metals was improved in the presence of melamine in polymeric matrix. The C-PMMA/Mel has high efficacy in the removal of ~94% of Pb at pH 6 for one hour. Noticeably, the adsorption performance of C-PMMA/Mel perfectly suited with Freundlich isotherm and the pseudo-second-order kinetic model. Additionally, the new materials showed no obvious loss in Pb(II) removal after 7 cycles.

Fabrication of binary g-C3N4/UU-200 composites with enhanced visible-light-driven photocatalytic performance toward organic pollutant eliminations

In this study, g-C₃N₄/UU-200 heterojunction photocatalysts displaying superior photocatalytic activity for organic pollutant elimination under white LED light irradiation were fabricated via an in situ solvothermal method. The successful construction of a heterojunction between g-C₃N₄ and UU-200 was evidenced by X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The improved photocatalytic degradation of rhodamine B (RhB) and tetracycline hydrochloride (TCH) over g-C₃N₄/UU-200 compared with that over the individual components can be attributed to the anchoring of the g-C₃N₄ layered structure on the UU-200 surface promoting the decrease of the bandgap of UU-200, as confirmed by ultraviolet–visible diffuse reflectance spectroscopy, and to the light-induced charge separation efficiency stemming from a suitable heterojunction structure, which was revealed by photoluminescence spectroscopy and electrochemical analyses. Specifically, the 40% g-C₃N₄/UU-200 composite showed the highest photocatalytic activity toward the degradation of RhB (97.5%) within 90 min and TCH (72.6%) within 180 min. Furthermore, this catalyst can be recycled four runs, which demonstrates the potential of the g-C₃N₄/UU-200 composite as an alternative visible-light-sensitive catalyst for organic pollutant elimination.

The binary g-C₃N₄/UU–200 heterojunction photocatalysts displaying superior photocatalytic activity for organic pollutant elimination under white LED light irradiation were fabricated via an in situ solvothermal method.

The pivotal role of defects in fabrication of polymeric carbon nitride homojunctions with enhanced photocatalytic hydrogen evolution

Fabrication of homojunctions is a cost-effective efficient way to enhance the photocatalytic performance of polymeric carbon nitride (CN), but the generation of defects upon synthesizing CN homojunctions and their roles in the homojunction fabrication were hardly reported. Herein, nitrogen-deficient CN homojunctions were simply synthesized by calcining dicyandiamide-loaded CN (prepared from urea and denoted as UCN) with dicyandiamide polymerizing into CN (denoted as DCN) and simultaneous formation of nitrogen vacancies in the surface of UCN. Fabrication of the nitrogen-deficient UCN (dUCN)/DCN homojunction depends on the nitrogen vacancy content in dUCN which can tune the energy band structure of dUCN from not matching to matching with that of DCN. The dUCN/DCN homojunction exhibits extended optical absorption and remarkably enhanced charge separation and photocatalytic H₂ evolution, compared with UCN and DCN. This work illustrates the pivotal role of defects in fabricating CN homojunctions and supplies a new facile way to synthesize nitrogen-deficient CN.

Metal-free n/n-junctioned graphitic carbon nitride (g-C3N4): a study to elucidate its charge transfer mechanism and application for environmental remediation

Graphitic carbon nitride (g-C₃N₄) has been regarded as a promising visible light-driven photocatalyst ascribable to its tailorable structures, thermal stability and chemical inertness. Enhanced photocatalytic activity is achievable by the construction of homojunction nanocomposites to reduce the undesired recombination of photogenerated charge carriers. In the present work, a novel g-C₃N₄/g-C₃N₄ metal-free homojunction photocatalyst was synthesized via hydrothermal polymerization. The g-C₃N₄/g-C₃N₄ derived from urea and thiourea demonstrated admirable photocatalytic activity towards rhodamine B (RhB) degradation upon irradiation of an 18 W LED light. The viability of the photoreaction with a low-powered excitation source highlighted the economic and environmental benefits of the process. The optimal g-C₃N₄/g-C₃N₄ homojunction photocatalyst exhibited a 2- and 1.8-fold increase in efficiency in relative to pristine g-C₃N₄ derived from urea and thiourea respectively. The enhanced photocatalytic performance is credited to the improved interfacial transfer and separation of electron-hole pairs across the homojunction interface. Furthermore, an excellent photochemical stability and durability is displayed by g-C₃N₄/g-C₃N₄ after three consecutive cycles. In addition, a plausible photocatalytic mechanism was proposed based on various scavenging tests. Overall, experimental results generated from this study is expected to intrigue novel research inspirations in developing metal-free homojunction photocatalysts to be feasible for large-scale wastewater treatment without compromising economically. Graphical abstract.

Preparation of phenyl group functionalized g-C3N4 nanosheets with extended electron delocalization for enhanced visible-light photocatalytic activity

Phenyl group functionalized g-C₃N₄ shows an improved light utilization and charges separation rate due to extended conjugation system, leading to a superior catalytic activity in a variety of photocatalytic systems.