Catalysts, Volume 14, Issue 6 (June 2024) – 30 articles

Direct upgrading of methane into value-added products is one of the most significant technologies for the effective transformation of hydrocarbon feedstocks in the chemical industry. Both oxidative and non-oxidative methane conversion are broadly useful approaches, though the two reaction pathways are quite distinguished. Oxidative coupling of methane (OCM) has been widely studied, but suffers from the low selectivity to C₂ hydrocarbons because of the overoxidation leading to undesired byproducts. Therefore, non-oxidative coupling of methane is a worthy alternative approach to be developed for the efficient, direct utilization of methane. Recently, heterogeneous catalysts comprising singly dispersed metal sites, such as single-atom catalysts (SAC) and surface organometallic catalysts (SOMCat), have been proven to be effectively active for direct coupling of methane to product hydrogen and C₂ products. In this context, this review summarizes recent discoveries of these novel catalysts and provides a perspective on promising catalytic processes for methane transformation via non-oxidative coupling. Full article

The preparation of CO${}_2$-containing polymers with improved degradation properties is still very challenging. An elegant method for preparing these polymers is to use CO${}_2$-containing monomers in ring-opening polymerizations (ROP) which are particularly gentle and energy-saving methods. However, cyclic carbonates are required for this which are not readily available. This paper therefore aims to present the optimization and comparison of two synthesis methods to obtain cyclic carbonates for ROP. Within this work, cyclic styrene carbonate was synthesized from readily available raw materials by using a Jacobsen catalyst for the reaction of styrene oxide and carbon dioxide or an organocatalyst for the transesterification of methyl carbonate with 1-phenyl-1,2-ethanediol. The latter performed with 100% selectivity to the desired styrene carbonate, which was succesfully tested in ROP, producing an amorphous thermoplastic polymer with a T${}_G$ of 185 ${}^{\circ }$C. Full article

This study proposes a straightforward strategy utilizing metal–organic frameworks (MOFs) to obtain efficient electrocatalysts for synthesizing C2 products (C₂H₄ and C₂H₅OH) via a CO₂ reduction reaction. Cu-MOF-74 was chosen as the precursor, while copper oxide nanoparticles were obtained through a calcination method. During the calcination process, by controlling the calcination conditions, the porous structure of the MOF framework was successfully retained, leading to CuO-400 with a high catalytic activity and C2 production efficiency. Compared to CuO-n formed by the calcination of Cu(NO₃)₂, CuO-400 derived from MOFs exhibits a 1.6 times higher C2 activity as an electrocatalytic material at −1.15 V vs. RHE. Full article

The rapid increase in the use and development of statistical design of experiments (DoE), particularly in pharmaceutical process development, has become increasingly important over the last decades. This rise aligns with Green Chemistry Principles, seeking reduced resource usage and heightened efficiency. In this study, we employed a comprehensive design of experiments (DoE) approach to optimize the catalytic conversion of 1-decene to n-decanal through direct Wacker-type oxidation using the previously determined efficient PdCl₂(MeCN)₂ catalytic system. The aim was to maximize selectivity and conversion efficiency. Through systematic variation of seven factors, including substrate amount, catalyst and co-catalyst amount, reaction temperature, reaction time, homogenization temperature, and water content, this study identified critical parameters influencing the process to direct the reaction toward the desired product. The statistical analysis revealed high significance for both selectivity and conversion, with surface diagrams illustrating optimal conditions. Notably, catalyst amount emerged as a pivotal factor influencing conversion, with reaction temperature and co-catalyst amount significantly affecting both conversion efficiency and selectivity. The refined model demonstrated strong correlations between predicted and observed values, highlighting the impact of these factors on both selectivity and conversion. Full article

This work investigates the electrocatalytic properties of carbon paste electrodes (CPEs) modified with ionic liquids (IL) and metallic ionic liquid (ILFe) for the hydrazine oxidation reaction (HzOR). The results indicate that ILFe significantly enhances the catalytic activity of the electrode, exhibiting catalysis towards hydrazine oxidation, reducing overpotential, and increasing reaction current. It is determined that the HzOR on the MWCNT/MO/ILFe electrode involves the transfer of four electrons, with high selectivity for nitrogen formation. Additionally, ILFe is observed to improve the wettability of the electrode surface, increasing its capacitance and reaction efficiency. This study highlights the advantages of ILFe-modified CPEs in terms of simplicity, cost-effectiveness, and improved performance for electrochemical applications, demonstrating how the ionic liquid catalyzes hydrazine oxidation despite its lower conductivity. Full article

Photocatalysis technology is an economical and effective new energy technology which depends on the conversion and storage of light energy through an energy transfer process or charge transfer process. Recently, organic semiconductor photocatalytic materials with the advantages of controllable structure, broad spectral response, designability, and flexibility have received wide attention. In particular, the organic polymeric materials containing poly-perylene diimides (PDI) show significant promise in the realm of photocatalysis due to their impressive catalytic capabilities and wide spectral reactivity. However, a poor charge separation and transportation (CST) process undermines their photocatalytic efficiency in most polymer photocatalysts, as well as in PDI photocatalysts. In this context, we propose a new strategy through regulating the monomer symmetry to construct highly efficient PDI photocatalysts. As proof-of-concept, a series of new PDI-based organic supramolecular photocatalytic materials with full visible spectral response from the perspectives of both the π-π conjugated structure and the symmetry of chain structure are successfully synthesized. Meanwhile, the structural compositions, morphology features, electrical properties, and photocatalytic performances of those obtained PDI photocatalysts were systematically studied. The results shown that the as-prepared PDI-1,5NDA exhibits 1.6-fold and 3.7-fold higher levels of photosynthesis of H₂O₂ activity than those of PDI-1,4NDA and PDI-PDA, respectively, which could be ascribe to its lower symmetry and large π-conjugate systems greatly enhances the separation of charge carriers. Full article

Pollution caused by antibiotics has brought significant challenges to the ecological environment. To improve the efficiency of the removal of tetracycline (TC) from aqueous solutions, a composite material consisting of TiO₂ and phosphoric acid-treated peanut shell biochar (p-BC) has been successfully synthesized in the present study by the sol-gel method. In addition, the composite material was characterized using various techniques, including scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) spectroscopy, X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) spectroscopy, and ultraviolet–visible diffuse reflectance spectroscopy (UV-vis DRS). The XPS and FTIR analyses revealed the formation of a new Ti–O–C bond, while the XRD analysis confirmed the presence of TiO₂ (with an anatase phase) in the composite material. Also, the PL analyses showed a notable decrease in the recombination efficiency of electrons and holes, which was due to the formation of a composite. This was further supported by the UV-vis DRS analyses, which revealed a decrease in bandgap (to 2.73 eV) of the composite material and led to enhanced light utilization and improved photocatalytic activity. Furthermore, the effects of pH, composite dosage, and initial concentration on the removal of TC were thoroughly examined, which resulted in a maximum removal efficiency of 95.3% under optimal conditions. Additionally, five consecutive cycle tests demonstrated an exceptional reusability and stability of the composite material. As a result of the experiments, the active species verified that ·O₂⁻ played a key role in the photodegradation of TC. Four possible degradation pathways of TC were then proposed. As a general conclusion, the TiO_2/p–BC composite can be used as an efficient photocatalyst in the removal of TC from aqueous solutions. Full article

Metal–organic frameworks (MOFs) have recently gained attention as a highly promising category of photocatalytic materials, showing great potential in the degradation of organic dyes such as Rhodamine B (RhB). Nonetheless, the mono-metal MOF materials in this application are often constrained by their limited light absorption capabilities and their propensity for recombination with carriers. The combination of different metal-based MOFs to form heterogeneous reactors could present a promising approach for the removal of dyes from water. In this work, a new CAU-17/MIL-100(Fe) Z-scheme heterojunction photocatalyst composed of two MOFs with the same ligands is reported to realize the efficient degradation of dyes in water. The combination of the two MOFs results in a significant enhancement of the surface open sites, optical responsivity range, and charge-separating efficiency through synergistic effects. In addition, the capture experiments conducted on the photocatalytic process have verified that ∙O₂⁻ and h⁺ are the primary active species. Consequently, CAU-17/MIL-100(Fe) exhibited excellent photocatalytic activity and stability. The degradation rate of the optimal CAU-17/MIL-100(Fe) photocatalyst was 34.55 times that of CAU-17 and 3.60 times that of MIL-100(Fe). Our work provides a new strategy for exploring the visible-light degradation of RhB in bimetallic MOF composites. Full article

The deactivation of active sites caused by high-temperature sintering and the deposition of a large amount of carbon are the main difficulties in the reforming of methane using Ni-based catalysts. La, as a promoter, has an ameliorating effect on the defects of Ni-based catalysts. In this article, the mechanism of action of Ni-based catalysts with the introduction of the rare-earth metal additive La was reviewed, and the effects of La on the methane-reforming performance of Ni-based catalysts were examined. The physical properties, alkalinity, and activity of Ni-based catalysts can be enhanced by the use of the auxiliary agent La, which promotes the conversion of CH₄ and CO₂ as well as the selectivity towards H₂ and CO formation in the reforming of methane. The reason why the Ni-based catalysts could maintain long-term stability in the presence of La was discussed. Furthermore, the current state of research on the introduction of different amounts of La in the reforming of methane at home and abroad was analyzed. It was found that 2–5 wt.% La is the most optimal quantity for improving the catalyst activity and stability, as well as the CO₂ chemisorption. The limitations and directions for future research in the reforming of methane were discussed. Full article

Researchers have focused on deriving environmentally benign materials from biomass waste and converting them into value-added materials. In this study, cellulosic crystals derived from sugarcane bagasse (SCB) are augmented with magnetite (M) nanoparticles. Following the co-precipitation route, the composite was prepared, and then the mixture was subjected to a green microwave solvent-less technique. Various mass ratios of SCB:M (1:1, 2:1, 3:1, 5:1, and 1:2) were prepared and efficiently utilized as photocatalysts. To look at the structural and morphological properties of the prepared samples, X-ray diffraction pattern (XRD), scanning electron microscopy (SEM), and elemental analysis were used to describe the composite fibers. SCB:M augmented with H₂O₂ as a Fenton reaction was used to eliminate Reactive blue 19 (RB19) from polluted water and was compared with pristine SCB and M. Additionally, the response surface methodology (RSM) statistically located and assessed the optimized parameters. The optimal operating conditions were recorded at pH 2.0 and 3:1 SCB: M with 40 mg/L and 100 mg/L of hydrogen peroxide. However, the temperature increase inhibits the oxidation reaction. The kinetic modeling fit showed the reaction following the second-order kinetic model with an energy barrier of 98.66 kJ/mol. The results show that such photocatalyst behavior is a promising candidate for treating textile effluent in practical applications. Full article

In this experimental study, diverse water-soluble Fe(III) complexes were synthesized and employed to catalyze the aquathermolysis of heavy oil. A ternary reaction system comprising heavy oil, water, and methanol was established to facilitate the process. Viscometry, thermogravimetric analysis, DSC, and elemental analysis were utilized to thoroughly investigate the treated heavy oil. The findings reveal that, under optimal conditions of water, catalyst, and methanol dosage, the viscosity of heavy oil can be significantly reduced by up to 88.22% after reacting at 250 °C for 12 h. Notably, apart from viscosity reduction, the catalytic aquathermolysis also effectively removes heteroatoms such as sulfur, nitrogen, and oxygen, enabling in situ modification and viscosity reduction of heavy oil. This study demonstrates the potential of water-soluble Fe(III) complexes in enhancing the efficiency of heavy oil extraction and processing. Full article

The effect of high concentrations of H₂S in sour natural gas on the catalytic dry reforming of methane (DRM) process has seldom been studied previously in the literature. Herein, several types of catalysts, including MgO, NiO/MgO, and LaNiO₃ in different states, were prepared for conducting DRM at 800 °C and 0.1 MPa in a feed of 20 vol% CO₂ and 20 vol% CH₄, and their catalytic performance under conditions of the absence and presence of H₂S was compared. A promotion effect of increasing H₂S concentration on both the conversions of CO₂ and CH₄ and the molar yields of CO and H₂ was observed on all the catalysts and was particularly remarkable on the MgO and the pristine NiO/MgO. For NiO/MgO, the addition of 15 vol% H₂S increased the conversion of CH₄ from 6.92% to 26.86% and CO₂ from 9.15% to 42.10%. While there was a significant decline in the catalytic activity of the reduced NiO/MgO and LaNiO₃ catalysts after adding H₂S, moderate reactant conversions were still sustained. The results of process analysis and catalyst structure characterization suggest that H₂S participation can contribute to the increment in CO₂ and CH₄ conversion, and active S-adsorbed species may play the key role of catalysis in reactions involving H₂S. Full article

New bifunctional cobalt catalysts for combined Fischer–Tropsch synthesis and hydroprocessing of hydrocarbons containing Pt were developed. To prepare catalysts in the form of a composite mixture, the FT synthesis catalyst Co-Al₂O₃/SiO₂ and ZSM-5 zeolite in the H-form were used as metal and acid components, respectively, with boehmite as a binder. The catalysts were characterized by various methods, such as XRD using synchrotron radiation, SEM, EDS, TEM and TPR. The effect of the Pt introduction method on the particle size and conditions for cobalt reduction was studied. The testing of catalysts in Fischer–Tropsch synthesis was carried out at a pressure of 2.0 MPa, a temperature of 240 and 250 °C, an H₂/CO ratio of 2 and a synthesis gas volumetric velocity of 1000 h⁻¹. It is shown that the method of introducing a hydrogenating metal by adjusting the nano-sized spatial structure of the catalyst determined the activity in the synthesis and group and fractional composition of the resulting products. It is established that the presence of Pt intensified the processes of synthesis and hydrogenation, including isomeric products, and reduced the content of unsaturated hydrocarbons. The application of Pt by impregnation onto the surface of the metal component of the catalysts provided the highest productivity for C₅₊ hydrocarbons, and for the acidic component, it enabled maximum cracking and isomerizing abilities. Full article

In this study, we prepared the SnO₂/ZnFe₂O₄ (SZ) composite magnetic photocatalyst via a two-step hydrothermal method. Structural and performance analyses revealed that SZ-5 with a ZnFe₂O₄ mass ratio of 5% (SZ-5) exhibited optimal photocatalytic activity, achieving a 72.6% degradation rate of Rhodamine B (RhB) solution within 120 min. SZ-5 consisted of irregular nano blocks of SnO₂ combined with spherical nanoparticles of ZnFe₂O₄, with a saturated magnetization intensity of 1.27 emu/g. Moreover, the specific surface area of SnO₂ loaded with ZnFe₂O₄ increased, resulting in a decreased forbidden bandwidth and expanded light absorption range. The construction of a Z-type heterojunction structure between SnO₂ and ZnFe₂O₄ facilitated the migration of photogenerated charges, reduced the recombination rate of electron-hole pairs, and enhanced electrical conductivity. During the photocatalytic reaction, RhB was degraded by·OH, O₂⁻, and h⁺, in which O₂⁻ played a major role. Full article

Alkaline seawater electrolysis has garnered significant attention as an efficient, green, and sustainable method for producing green hydrogen in recent years. However, the lack of highly active anodes in seawater electrolysis to prevent chloride oxidation reactions has limited its commercial application. In this study, Au single atoms were deposited on NiCoFeS through the electrochemical deposition method. The optimized catalyst exhibited significantly enhanced activity in seawater electrolyte; the Au@NiCoFeS catalyst achieved a current density of 10 mA/cm² with only 183 mV and maintained its performance without degradation for 250 h at a current density of 200 mA/cm², with no corrosion observed on either the catalyst or the substrate. Full article

Gd/Fe-SnO₂ nanopowders as novel photocatalysts for the active removal of Rose Bengal dye and methyl parathion pesticide were synthesized with a low-cost coprecipitation route. The X-ray diffraction analysis of SnO₂, Sn_0.96Gd_0.02Fe_0.02O₂ and Sn_0.94Gd_0.02Fe_0.04O₂ nanopowders proved the formation of a tetragonal phase of tin oxide with average crystallite sizes in the range of 13–18 nm. The Fourier transform infrared (FTIR) spectra of all samples displayed the characteristic absorption bands of SnO₂. The nanopowder of the pure SnO₂ sample, as seen in its transmission electron microscope (TEM) image, contains spherical-like particles of variable sizes. The TEM images of the Sn_0.96Gd_0.02Fe_0.02O₂ and Sn_0.94Gd_0.02Fe_0.04O₂ powders revealed the synthesis of fine spherical nanoparticles. Based on the TEM images, the average particle size of the pure, (Gd, 2 wt% Fe) and (Gd, 4 wt% Fe) codoped SnO₂ nanopowders was estimated to be 14, 10 and 12 nm, respectively. After the addition of (Gd, 2 wt% Fe) and (Gd, 4 wt% Fe) to the SnO₂ structure, the band gap energy of SnO₂ was reduced from 3.4 eV to 2.88 and 2.82 eV, respectively. Significantly, the Sn_0.96Gd_0.02Fe_0.02O₂ nanocatalyst exhibited a high removal efficiency of 98 and 96% for Rose Bengal dye and methyl parathion pesticide after activation by sunlight for 35 and 48 min, respectively. Furthermore, this catalyst has shown perfect mineralization as well as high stability properties for the treatment of Rose Bengal dye and methyl parathion pesticide. These results suggest the suitability of the Sn_0.96Gd_0.02Fe_0.02O₂ nanocatalyst for the treatment of agriculture and industrial effluent under sunlight light energy. Full article

A new catalyst, Sm₂NdSbO₇, was synthesized for the first time by solid-phase sintering. The study utilized X-ray diffraction, transmission electron microscope energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy to examine the structural characteristics of monocrystal BiDyO₃, monocrystal Sm₂NdSbO₇ and Sm₂NdSbO₇/BiDyO₃ heterojunction photocatalysts (SBHP) prepared by solid-phase sintering. The Sm₂NdSbO₇ photocatalyst owned a pyrochlorite structure, belonged to the face-centered cubic crystal system, possessed a space group of Fd3m and a bandgap width of 2.750 eV. After 145 min of visible light irradiation (145-VLIRD), the removal rate (RMR) of methyl parathion (MP) or total organic carbon of SBHP was 100% or 97.58%, respectively. After 145-VLIRD, the photocatalytic degradation rates of SBHP to MP were 1.13 times, 1.20 times, and 2.43 times higher than those of the Sm₂NdSbO₇ photocatalyst, the BiDyO₃ photocatalyst, and the nitrogen-doped TiO₂ catalyst, respectively. The experimental results showed that SBHP had good photocatalytic activity. After four cycles of cyclic degradation experiments with SBHP, the elimination rates of MP were 98.76%, 97.44%, 96.32%, and 95.72%, respectively. The results showed that SBHP had good stability. Finally, the possible degradation pathways and degradation mechanisms of MP were speculated. In this study, we successfully developed a high-efficiency heterojunction catalyst which responded to visible light and possessed significant photocatalytic activity. The catalyst could be used in photocatalytic reaction system for eliminating the harmful organic pollutants from wastewater. Full article

The efficient hydrogenation of N-heterocycles with H₂ under mild conditions remains a significant challenge. In this work, polyphosphazene (PZs) microspheres, novel organic–inorganic hybrid materials possessing unique –P=N– structural units and a diverse range of side groups, were used to serve as support for the design of a stable and efficient Pd nanocatalyst (Pd/PZs). The PZs microspheres were prepared by self-assembly induced by precipitation polymerization, and Pd nanoparticles were grown and loaded on the support by a chemical reduction process. Several characterization techniques, including XRD, FTIR, SEM, TEM, XPS, BET and TGA, were used to study the structural features of the nanocomposites. The results revealed that Pd nanoparticles were uniformly distributed on the PZs microspheres, with primary sizes ranging from 4 to 9 nm based on the abundance of functional P/N/O groups in PZs. Remarkably high catalytic activity and stability were observed for the hydrogenation of quinoline compounds using the Pd/PZs nanocatalyst under mild conditions. Rates of 98.9% quinoline conversion and 98.5% 1,2,3,4-tetrahydroquinoline selectivity could be achieved at a low H₂ pressure (1.5 bar) and temperature (40 °C). A possible reaction mechanism for quinoline hydrogenation over Pd/PZs was proposed. This work presents an innovative approach utilizing a Pd-based nanocatalyst for highly efficient multifunctional hydrogenation. Full article

Ionic liquid modification for carbon-supported platinum (Pt/C) electrocatalysts to enhance their oxygen reduction reaction (ORR) activity has been well recognized. However, the research has only been reported on the low-Pt-loading Pt/C electrocatalysts, e.g., 20 wt%, while in practical applications, usually high-Pt-loading Pt/C electrocatalysts of 45–60 wt% are used. In this work, ionic liquid modification is systematically investigated for a Pt/C electrocatalyst with 60 wt% Pt loading for its ORR activity in the cathode in proton exchange membrane fuel cells (PEMFCs). Various adsorption amounts are studied on the catalyst surface. Different modification behavior is found. Mechanism exploration shows that the adsorption of ionic liquid mainly happens on the Pt electrocatalyst surface and in the micropores of the carbon support. The highest fuel cell power performance is achieved at an ionic liquid loading of 7 wt%, which is much higher than the 3 wt% reported for the low-Pt-loading Pt/C. Full article

The extensive use of single-atom catalysts (SACs) has appeared as a significant area of investigation in contemporary study. The single-atom catalyst, characterized by its maximum atomic proficiency and great discernment of the transition-metal center, has a unique combination of benefits from both heterogeneous and homogeneous catalysts. Consequently, it effectively bridges the gap between these two types of catalysts, leveraging their distinctive features. The utilization of SACs immobilized on graphene substrates has garnered considerable interest, primarily because of their capacity to facilitate selective and efficient photocatalytic processes. This review aims to comprehensively summarize the progress and potential uses of SACs made from graphene in photocatalytic carbon dioxide (CO₂) reduction and hydrogen (H₂) generation. The focus is on their contribution to converting solar energy into chemical energy. The present study represents the various preparation methods and characterization approaches of graphene-based single-atom photocatalyst This review investigates the detailed mechanisms underlying these photocatalytic processes and discusses recent studies that have demonstrated remarkable H₂ production rates through various graphene-based single-atom photocatalysts. Additionally, the pivotal roleof theoretical simulations, likedensity functional theory (DFT), to understand the structural functional relationships of these SACs are discussed. The potential of graphene-based SACs to revolutionize solar-to-chemical energy conversion through photocatalytic CO₂ reduction and H₂ production is underscored, along with addressing challenges and outlining future directions for this developing area of study. By shedding light on the progress and potential of these catalysts, this review contributes to the collective pursuit of sustainable and efficient energy conversion strategies to mitigate the global climate crisis. Full article

In this study, 2-t-butyl-4-arylimino-2,3-dihydroacridylnickel dibromides were synthesized by nickel-template one-pot condensation, and well characterized along with the single-crystal X-ray diffraction to one representative complex, revealing a distorted tetrahedral geometry around nickel. When activated with modified methylaluminoxane (MMAO), all nickel complexes exhibited high activities (up to 1.91 × 10⁶ g mol⁻¹ (Ni) h⁻¹) toward major trimerization of ethylene. When activated with ethylaluminum dichloride (EtAlCl₂), however, the title complexes performed good activities (up to 1.05 × 10⁶ g mol⁻¹ (Ni) h⁻¹) for selective dimerization of ethylene. In comparison to analogous nickel complexes, higher activities were achieved with the substituent of t-butyl group, especially in the rare case of nickel complexes performing trimerization of ethylene. Full article

Using a p-n heterojunction is one of the efficient methods to increase charge transfer in photocatalysis applications. So, herein, p-type UiO-66 (NH₂) and n-type CuFe₂O₄ (CFO) are used to form an effective p-n heterojunction. Due to their poor charge separation in their pristine form, both UiO-66 (NH₂) and CFO materials cannot produce hydrogen; however, the composite p-n heterojunction formed between these materials makes fast charge separation and so hydrogen is efficiently produced. The optimized catalyst UCFO 25% produces a maximum of 62.5 µmol/g/h hydrogen in an aqueous methanol solution. The formation of a p-n heterojunction is confirmed by Mott–Schottky analysis and optical properties, crystallinity and the local atomic environment of the material was analyzed by various analytical tools like UV-Vis spectroscopy, XRD, and XANES. Full article

Water pollution is one of the main challenges currently facing scientists around the world because of the rapid growth in industrial activities. On this basis, 2D nanolayered and nanohybrid structures, which are based on a ternary system of nickel–titanium–zinc, are considered favorable sources for designing effective nanocomposites for the photocatalytic degradation of industrial pollutants in a short period of time. These nanocomposites were designed by modifying two-dimensional nanolayers to produce a three-dimensional porous structure of multi-doped Ni/Ti-ZnO nanocomposites. Additionally, another additive was produced by constructing nanohybrids of nickel–titanium–zinc combined with a series of hydrocarbons (n-capric acid, myristic acid, stearic acid, suberic acid, and sebacic acid). Energy-dispersive X-ray spectrometry, X-ray diffraction, scanning electron microscopy, infrared spectroscopy, and thermal analyses confirmed the growth of the nanolayered and nanohybrid materials in addition to the production of nanocomposites. The positive role of the dopants (nickel and titanium) in producing an effective photocatalyst was observed through a significant narrowing of the band gap of zinc oxide to 3.05–3.10 eV. Additionally, the high photocatalytic activity of this nanocomposite enabled the complete removal of colored dye from water after 25 min of UV radiation. In conclusion, this study proposes an unconventional approach for designing new optical nanocomposites for purifying water. Additionally, it suggests a novel supporting method for designing new kinds of nanohybrids based on multi-metals and organic acids. Full article

A novel protocol facilitated by Na₂SO₃ that enhances the efficiency of palladium-catalyzed Heck coupling and the homo-coupling reactions of arylhydrazines. This innovative method enables the effective construction of a diverse array of cinnamate derivatives and biphenyl compounds. Notably, these transformative reactions proceed smoothly at room temperature, leveraging the activation of C-N bonds. This technique not only streamlines the synthesis process but also expands our understanding and expertise in the realm of coupling reactions. Full article

Zinc oxide nanoparticles (ZnO NPs) are becoming an innovative agent in biological and environmental applications due to its unique characteristics, biocompatibility, low cost and toxicity. In this study, the composite ZnO NPs using Rhododendron arboreum (R. arboreum) stem bark were synthesized and characterized for UV–visible spectroscopy (UV-vis), Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The biomedical assessment of the synthesized nanoparticles showed zones of inhibition of 23 ± 0.09, 18 ± 0.1 and 16 ± 0.05 mm, against the Klebsiella pneumoniae (K. pneumoniae), Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) strains, respectively. Likewise, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values against K. pneumoniae, S. aureus, and E. coli were found to be 34 ± 0.21 and 72.71 ± 0.47, 47 ± 0.11 and 94.86 ± 0.84 and 94 ± 0.18 and 185.43 ± 0.16 µg/mL, respectively. The biosynthesized ZnO NPs resulted in significant eradication of the outer and inner membranes of the tested bacterial cells. In addition, the environmental application of the synthesized ZnO NPs also showed time-dependent photocatalytic degradation activity and revealed 65% methyl orange dye degradation with an irradiation period of 6 h. The findings of this study suggest the suitability of the novel R. arboreum stem bark-based ZnO NPs as an effective ameliorant against bactericidal activities and photocatalytic potential for the removal of potentially toxic substances from water. Full article

Biodiesel is a mixture of fatty acid alkyl esters (FAAEs) mainly produced via transesterification reactions among triglycerides and short-chain alcohols catalyzed by chemical catalysts (e.g., KOH, NaOH). Lipase-assisted enzymatic transesterification has been proposed to overcome the drawbacks of chemical synthesis, such as high energy consumption, expensive separation of the catalyst from the reaction mixture and production of large amounts of wastewater during product separation and purification. However, one of the main drawbacks of this process is the enzyme cost. In recent years, nano-immobilized lipases have received extensive attention in the design of robust industrial biocatalysts for biodiesel production. To improve lipase catalytic efficiency, magnetic nanoparticles (MNPs) have attracted growing interest as versatile lipase carriers, owing to their unique properties, such as high surface-to-volume ratio and high enzyme loading capacity, low cost and inertness against chemical and microbial degradation, biocompatibility and eco-friendliness, standard synthetic methods for large-scale production and, most importantly, magnetic properties, which provide the possibility for the immobilized lipase to be easily separated at the end of the process by applying an external magnetic field. For the preparation of such effective magnetic nano-supports, various surface functionalization approaches have been developed to immobilize a broad range of industrially important lipases. Immobilization generally improves lipase chemical-thermal stability in a wide pH and temperature range and may also modify its catalytic performance. Additionally, different lipases can be co-immobilized onto the same nano-carrier, which is a highly effective strategy to enhance biodiesel yield, specifically for those feedstocks containing heterogeneous free fatty acids (FFAs). This review will present an update on the use of magnetic iron oxide nanostructures (MNPs) for lipase immobilization to catalyze transesterification reactions for biodiesel production. The following aspects will be covered: (1) common organic modifiers for magnetic nanoparticle support and (2) recent studies on modified MNPs-lipase catalysts for biodiesel production. Aspects concerning immobilization procedures and surface functionalization of the nano-supports will be highlighted. Additionally, the main features that characterize these nano-biocatalysts, such as enzymatic activity, reusability, resistance to heat and pH, will be discussed. Perspectives and key considerations for optimizing biodiesel production in terms of sustainability are also provided for future studies. Full article

Excessive emissions of carbon dioxide have led to the greenhouse effect and global warming. Reducing carbon dioxide into high-value-added chemicals through solar energy is a promising approach. Herein, a g-C₃N₄/TiO₂ heterojunction photocatalyst with efficient electron transfer is designed for photocatalytic CO₂ reduction. The CH₄ (18.32 µmol·h⁻¹·g⁻¹) and CO (25.35 µmol·h⁻¹·g⁻¹) evolution rates of g-C₃N₄/TiO₂ are higher than those of g-C₃N₄ and TiO₂. The enhanced photocatalytic CO₂ reduction performance is attributed to the efficient charge carrier transfer in the g-C₃N₄/TiO₂ heterojunction. The electron transfer route was verified by in situ irradiated X-ray photoelectron spectroscopy (XPS). The photocatalytic CO₂ reduction mechanism on g-C₃N₄/TiO₂ was investigated by in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). This work provides a strategy for designing a polymer/metallic oxide heterojunction with efficient electron transfer for enhanced photocatalytic CO₂ reduction. Full article

In this study, graphene quantum dots (GQDs) have been incorporated into the g-C₃N₄/ZIF-67 heterojunction system as a photosensitizer to enhance photocatalytic conversion of CO₂-to-CO. The GQDs are deposited onto the surface of g-C₃N₄/ZIF-67 using a simple water bath procedure. As expected, GQDs/g-C₃N₄/ZIF-67 presents outstanding performance in CO₂ photoreduction. Among the GQDs/g-C₃N₄/ZIF-67 ternary photocatalysts, 7 GQDs-CN/ZIF-67 exhibits the best photocatalytic CO₂ reduction ability with a CO yield of 51.71 μmol g⁻¹, which is 5.05 and 1.87 times more than pristine g-C₃N₄ (10.24 μmol g⁻¹) and g-C₃N₄/ZIF-67 (27.65 μmol g⁻¹), respectively. This result shows that upon combination of GQDs with ZIF-67/g-C₃N₄, GQDs can be used as photosensitizers to improve the optical absorption capacity of the photocatalyst. Furthermore, GQDs serve as electron channels, facilitating the transport of photo-induced electrons from ZIF-67 to g-C₃N₄, which promotes photogenerated carrier separation efficiency. This study innovatively adds GQDs to the heterojunction and applies the prepared ternary composite to the CO₂ photoreduction, which inspires a novel direction for the design of non-noble metal photocatalysts. Full article