Functionalization of nitrogen-doped graphene quantum dot: A sustainable carbon-based catalyst for the production of cyclic carbonate from epoxide and CO2

A series of organic compounds were successfully immobilized on an N-doped graphene quantum dot (N-GQD) to prepare a multifunctional organocatalyst for coupling reaction between CO₂ and propylene oxide (PO). The simultaneous presence of halide ions in conjunction with acidic- and basic-functional groups on the surface of the nanoparticles makes them highly active for the production of propylene carbonate (PC). The effects of variables such as catalyst loading, reaction temperature, and structure of substituents are discussed. The proposed catalysts were characterized by different techniques, including Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy/energy dispersive X-ray microanalysis (FESEM/EDX), thermogravimetric analysis (TGA), elemental analysis, atomic force microscopy (AFM), and ultraviolet-visible (UV-Vis) spectroscopy. Under optimal reaction conditions, 3-bromopropionic acid (BPA) immobilized on N-GQD showed a remarkable activity, affording the highest yield of 98% at 140°C and 10⁶ Pa without any co-catalyst or solvent. These new metal-free catalysts have the advantage of easy separation and reuse several times. Based on the experimental data, a plausible reaction mechanism is suggested, where the hydrogen bonding donors and halogen ion can activate the epoxide, and amine functional groups play a vital role in CO₂ adsorption.

Recent Advances in Copper-Based Solid Heterogeneous Catalysts for Azide-Alkyne Cycloaddition Reactions

The copper(I)-catalyzed azide−alkyne cycloaddition (CuAAC) reaction is considered to be the most representative ligation process within the context of the “click chemistry” concept. This CuAAC reaction, which yields compounds containing a 1,2,3-triazole core, has become relevant in the construction of biologically complex systems, bioconjugation strategies, and supramolecular and material sciences. Although many CuAAC reactions are performed under homogenous conditions, heterogenous copper-based catalytic systems are gaining exponential interest, relying on the easy removal, recovery, and reusability of catalytically copper species. The present review covers the most recently developed copper-containing heterogenous solid catalytic systems that use solid inorganic/organic hybrid supports, and which have been used in promoting CuAAC reactions. Due to the demand for 1,2,3-triazoles as non-classical bioisosteres and as framework-based drugs, the CuAAC reaction promoted by solid heterogenous catalysts has greatly improved the recovery and removal of copper species, usually by simple filtration. In so doing, the solving of the toxicity issue regarding copper particles in compounds of biological interest has been achieved. This protocol is also expected to produce a practical chemical process for accessing such compounds on an industrial scale.

Self-Supporting g-C3N4 Nanosheets/Ag Nanoparticles Embedded onto Polyester Fabric as “Dip-Catalyst” for Synergic 4-Nitrophenol Hydrogenation

Herein, we report the design of a cost-effective catalyst with excellent recyclability, simple recuperation and facile recovery, and the examination between the reaction cycles via the development of self-supporting g-C3N4 nanosheets/Ag NPs polyester fabric (PES) using a simple, facile and efficient approach. PES fabrics were coated via a sono-coating method with carbon nitride nanosheets (GCNN) along with an in situ setting of Ag nanoparticles on PES coated GCNN surface producing PES-GCNN/Ag0. The elaborated textile-based materials were fully characterized using FTIR, 13C NMR, XRD, TGA, SEM, EDX, etc. Catalytic performance of the designed “Dip-Catalyst” demonstrated that the as-prepared PES-GCCN/Ag0 has effectively catalyzed the hydrogenation of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of NaBH4. The 3 × 3 cm2 PES-GCNN/Ag0 showed the best catalytic activity, displaying an apparent rate constant (Kapp) equal to 0.43 min−1 and more than 10 reusability cycles, suggesting that the prepared catalyst-based PES fabric can be a strong nominee for sustainable chemical catalysis. Moreover, the coated fabrics exhibited appreciable antibacterial capacity against Staphylococcus epidermidis (S. epidermidis) and Escherichia coli (E. coli). The present study opens up new opportunities for the future design of a low cost and large-scale process of functional fabrics.

Abundant hydroxyl groups decorated on nitrogen vacancy-embedded g-C3N4 with efficient photocatalytic hydrogen evolution performance

Engineering hydroxyl and N vacancies on g-C₃N₄ led to dual mitigation of the recombination rate of photogenerated carriers, which was achieved by enriched hydroxyl groups trapping the holes and stable N vacancies capturing the electrons.

Pyrene-based ammonium bromides combined with g-C3N4 for the synergistically enhanced fixation reaction of CO2 and epoxides

A new type of pyrene-based ammonium bromides (PABs) was synthesized via the reaction of bromomethyl pyrene and tertiary amines with different alkyl chains combined with graphitic carbon nitride (g-C₃N₄) through π–π stacking interactions. The new pyrene-based ammonium bromides were investigated both in homogenous phase and heterogeneous phase combining with g-C₃N₄ for the CO₂ fixation reaction of epoxides under mild conditions. Obviously, the combination was proved to be an efficient system for the conversion of epoxides. The interaction between g-C₃N₄ and PABs was confirmed by quantum chemical calculations. g-C₃N₄/Py-C₁₂ exhibited an excellent yield of cyclic carbonates (above 93%) at 80 °C, atmospheric pressure and solvent-free conditions. A preliminary kinetic study was performed using g-C₃N₄/Py-C₁₂ and the activation energy was calculated to be 61.5 kJ mol⁻¹.

The synergistic interaction of g-C₃N₄ and PABs plays an important role in the CO₂ fixation reaction with epoxides.

A Metal-Free Carbon-Based Catalyst: An Overview and Directions for Future Research

Metal-free carbon porous materials (CPMs) have gained the intensive attention of scientists and technologists because of their potential applications, ranging from catalysis to energy storage. Various simple and facile strategies are proposed for the preparation of CPMs with well-controlled sizes, shapes, and modifications on the surface. The extraordinary tenability of the pore structure, the environmental acceptability, the unique surface and the corrosion resistance properties allow them to be suitable materials for a large panel of catalysis applications. This review briefly outlines the different signs of progresses made towards synthesizing CPMs, and their properties, including catalytic efficiency, stability, and recyclability. Finally, we make a comparison of their catalytic performances with other nanocomposites, and we provide an outlook on the expected developments in the relevant research works.

Comprehensive insight into the support effect of graphitic carbon nitride for zinc halides on the catalytic transformation of CO2into cyclic carbonates

Zinc halides are anchored on a g-C₃N₄support and efficiently catalyze cycloaddition of CO₂with epoxides to cyclic carbonates.

Supported ZnBr2 and carbon nitride bifunctional complex catalysts for the efficient cycloaddition of CO2 with diglycidyl ethers

Bifunctional catalysts with large surface areas performed well in the cycloaddition of CO₂ and bisepoxides under solvent and co-catalyst free conditions.

Microwave assisted in situ decoration of a g-C3N4 surface with CdCO3 nanoparticles for visible light driven photocatalysis

Graphitic carbon nitride (g-C₃N₄) supported cadmium carbonate (CdCO₃) as an organic–inorganic hybrid nanophotocatalyst was realised by an in situ microwave heating method.

g-C3N4 and tetrabutylammonium bromide catalyzed efficient conversion of epoxide to cyclic carbonate under ambient conditions

A g-C₃N₄ and n-Bu₄N⁺Br⁻ combination was found to be an efficient catalyst for the conversion of epoxides to cyclic carbonates under CO₂ filled balloon conditions.