Amine-functionalized Schiff base covalent organic frameworks supported PdAuIr nanoparticles as high-performance catalysts for formic acid dehydrogenation and hexavalent chromium reduction.

Formic acid (FA) holds significant potential as a liquid hydrogen storage medium. However, it is important to improve the reaction rates and extend the practical applications of FA dehydrogenation and Cr(VI) reduction through the development of efficient heterogeneous catalysts. This study reports the synthesis of a uniformly dispersed PdAuIr nanoparticles (NPs) catalyst loaded with amine groups covalent organic frameworks (COFs). The alloyed NPs demonstrated exceptional effectiveness in FA dehydrogenation rate and Cr(VI) reduction. The initial turnover of frequency (TOF) value for FA dehydrogenation without additives was 9970 h-1 at 298 K, the apparent activation energy (Ea) was 30.3 kJ/mol and the rate constant (k) for Cr(VI) reduction was 0.742 min-1. Additionally, it showcased the ability to undergo recycling up to six times with minimal degradation in performance. The results indicate that its remarkable catalytic performance can be attributed primarily to the favorable mass transfer attributes of the aminated COFs supports, the strong metal-support interaction (SMSI), and the synergistic effects among the metals. This study offers a novel perspective on the advancement of efficient and durable heterogeneous catalysts with diverse capabilities, thereby making significant contributions to the fields of energy and environmental preservation.

Synthesis of Renewable High-Density Fuel with Vanillin and Cyclopentanone Derived from Hemicellulose.

1,3-bis(cyclohexylmethyl)cyclopentane, a renewable high-density fuel, was first produced in a high overall carbon yield (79.5%) with vanillin and cyclopentanone, which can be derived from biomass. The synthetic route used in this work contains two steps. In the first step, 2,5-bis(4-hydroxy-3-methoxybenzylidene)cyclopentanone was synthesized by aldol condensation of vanillin and cyclopentanone under the catalysis of sulphuric acid. Over the optimized condensation, a high carbon yield (82.6%) of 2,5-bis(4-hydroxy-3-methoxybenzylidene) cyclopentanone was achieved at 80 ºC. In the second step, 2,5-bis(4-hydroxy-3-methoxybenzylidene) cyclopentanone was hydrodeoxygenated over the Pd/HY catalyst in cyclohexane as solvent. High carbon yields of 1,3-bis(cyclohexylmethyl)cyclopentane (96.2%) was obtained. The polycycloalkane mixture as obtained has a density of 0.943 g mL-1 and a freezing point of -35 °C. It can be blended into conventional high-density fuels (e.g., JP-10) for rockets and missile propulsion as a potential application.

Research progress of catalysts for aldol condensation of biomass based compounds.

Research progress of catalysts of the aldol condensation reaction of biomass based compounds is summarized for the synthesis of liquid fuel precursors and chemicals. In summary, an acidic catalyst, alkaline catalyst, acid-base amphoteric catalyst, ionic liquid and other catalysts can catalyze the aldol condensation reaction. The aldol condensation reaction catalyzed by an acid catalyst has the problems of low conversion and low yield. The basic catalyst catalyzes the aldol condensation reaction with high conversion and yield, but the existence of liquid alkali is difficult to separate from the product. The reaction temperature needed for oxide and hydrotalcite alkali is relatively high. The basic resin has good catalytic activity and at a low reaction temperature, and is easy to separate from the target product. Acid-base amphoteric catalysts have received extensive attention from researchers for their excellent activity and selectivity. Ionic liquid is a new type of material, which can also be used for the aldol condensation reaction. In the future application of aldol condensation, the development of strong alkaline resin is a good research direction.

High-Performance Integrated rGO-[Polymeric Ionic Liquid] [Heteropolyanions] for Catalytic Degradation of Azo Dyes.

Polymeric ionic liquid (such as poly[ViEtIm]Br)-modified reduced graphene oxide (rGO), rGO-poly[ViEtIm]Br, was nominated as an open carrier to construct a degradation platform. The large specific surface of rGO together with the anion-exchange property of poly[ViEtIm]Br terminals led to the wide growth of heteropolyanions (like [PW12O40]3-, [PMo12O40]3-, and [SiW12O40]4-), thus assembling the integrated catalyst rGO-poly[ViEtIm][heteropolyanions]. The grafted poly[ViEtIm]Br provided an anchor point to interlink the polar heteropolyanions and the nonpolar rGO substrate, endowing this graphene-based catalyst with excellent dispersibility. The adequate exposure of heteropolyanions further promoted the decolorization capability during the degradation procedure. Morphology, structure, and properties of materials were confirmed and monitored via transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible (UV-vis) spectroscopy, etc. rGO-poly[ViEtIm][PW12O40] was selected as the optimal catalyst with degradation efficiency toward methyl orange reaching 98.7% in 3 h. In addition, the excellent structural stability of the catalyst improved the decolorization efficiency, which reached 95% after recycling five times.

Antibacterial and plant growth-promoting properties of novel Fe3O4/Cu/CuO magnetic nanoparticles.

In this work, an Fe3O4/Cu/CuO (FC) antibacterial nano-agent was synthesized in a "one-pot" approach using copper sulfate and ferric chloride as raw materials, and it was studied using TEM, XRD, XPS, UV-vis, and VSM methods. The antibacterial activity and mechanism of FC were studied, using a commercially available Bordeaux mixture as a control. The effects of an FC on mung bean development and its toxicity to human mammary epithelial cells were also investigated. The results revealed that FC could break the cell walls of E. coli and S. aureus, quadrupling the antibacterial activity of the Bordeaux combination. Furthermore, it was shown that FC might improve the germination, root development, and chlorophyll content of mung bean seeds while being 1/8 as hazardous to human mammary epithelial cells as the Bordeaux combination. The as-prepared FC can replace the Bordeaux combination in the management of agroforestry pathogens.

Synthesis of renewable diesel and jet fuel range alkanes using 2-methylfuran and cyclohexanone.

New solid acid catalysts were prepared by bisphenol A, paraformaldehyde and chlorosulfonic acid, and applied to hydroxylalkylation/alkylation (HAA) of 2-methylfuran (2-MF) and cyclohexanone. After optimizing the reaction conditions, the conversion of 2-MF reached 99% and the yield of 5,5'-(cyclohexane-1,1-diyl)bis(2-methylfuran) acquired 98%. The activity and catalytic efficiency were higher than those of Amberlyst 15 and Amberlyst 36 resins, which could be rationalized by high acid strength. At the same time, the catalysts were characterized by acid-base titration and FTIR. Hydrodeoxygenation (HDO) of HAA products of 2-methylfuran and cyclopentanone were processed on the Ni/SiO2 catalyst prepared by wet impregnation method to further convert into aviation kerosene, and the yield reached 93%.

Mesoporous magnetic g-C3N4 nanocomposites for photocatalytic environmental remediation under visible light.

Mesoporous magnetic Fe3O4/g-C3N4 nanocomposites were synthesized by a facile precipitation method using deionized water as solution. And the prepared magnetic materials were characterized by mean of various detection methods. At the same time, the photocatalytic activity of the synthetic material as photocatalyst under visible light was tested by taking the degradation of rhodamine B in water as a mark. Results show that as-synthesized Fe3O4/g-C3N4 nanocomposites have high specific surface areas of about 5-10.5 times that of pure g-C3N4 and high saturation magnetizations, which can ensure the smooth recovery of used nanomaterials under the action of external magnetic field. The addition of Fe3O4 greatly extents the response range of g-C3N4 nanomaterials to visible light and reduces the recombination rate of photoinduced electron-hole pairs. Meanwhile, the photocatalytic activity of the synthetic materials increases so that the degradation ratio of rhodamine B in water reached 97.6% after 4 h visible light irradiation. Furthermore, prepared magnetic Fe3O4/g-C3N4 nanocomposites have also excellent stability so that the degradation ratio of rhodamine B was almost not reduce after 5 times of continuous reuse of photocatalyst. Free radical scavenging experiments shows that hydroxyl groups are the main free radicals of photocatalytic reaction, peroxyradicals and holes play the secondary role. Therefore, it can be predicted that the synthesized mesoporous magnetic Fe3O4/g-C3N4 nanomaterials will have a broad application prospect in environmental remediation.

Fabrication of CdS-SBA-15 nanomaterials and their photocatalytic activity for degradation of salicylic acid under visible light.

CdS-SBA-15 nanomaterials were synthesized by solvothermal method using cadmium nitrate as cadmium source and thiourea as sulfur source. The properties of as-prepared materials were characterized by means of XRD, FTIR, TEM, XPS, N2 physisorption, UV-Vis DRS and PL spectra, etc. The results show as-synthesized materials have partially ordered mesoporous structure, larger specific surface area, and higher content of CdS and good crystallinity. The combination of SBA-15 and CdS did almost no reduction in the absorption light range of CdS, but greatly increased the photocapacity of the composite. The synergistic effect of CdS and SBA-15 leads to improving the photocatalytic degradation activity of salicylic acid under visible light. When the photocatalyst was 30 mg (0.75 g/L) and the concentration of salicylic acid was 10 mg/L, the maximum degradation efficiency of salicylic acid was 84.93% after 6 h of light. Photocatalytic reaction has a lower activation energy (2.90 kJ/mol), activation enthalpy (3.13 kJ/mol) and activation entropy (-281.00 J/(mol K)). The photocatalytic mechanism study demonstrates that superoxide radicals (O2•-) are the most key active species, e- and h+ have something to do with the photocatalytic reaction, while ·OH has little to do with the photocatalytic reaction. In sum, the protection effect of SBA-15 on CdS nanomaterials makes the composite have a higher photolumination intensity and a higher photocatalytic activity.

Effect of NH3 and HCOOH on the H2O2 + HO → HO2 + H2O reaction in the troposphere: competition between the one-step and stepwise mechanisms.

The H2O2 + HO → HO2 + H2O reaction is an important reservoir for both radicals of HO and HO2 catalyzing the destruction of O3. Here, this reaction assisted by NH3 and HCOOH catalysts was explored using the CCSD(T)-F12a/cc-pVDZ-F12//M06-2X/aug-cc-pVTZ method and canonical variational transition state theory with small curvature tunneling. Two possible sets of mechanisms, (i) one-step routes and (ii) stepwise processes, are possible. Our results show that in the presence of both NH3 and HCOOH catalysts under relevant atmospheric temperature, mechanism (i) is favored both energetically and kinetically than the corresponding mechanism (ii). At 298 K, the relative rate for mechanism (i) in the presence of NH3 (10, 2900 ppbv) and HCOOH (10 ppbv) is respectively 3-5 and 2-4 orders of magnitude lower than that of the water-catalyzed reaction. This is due to a comparatively lower concentration of NH3 and HCOOH than H2O which indicates the positive water effect under atmospheric conditions. Although NH3 and HCOOH catalysts play a negligible role in the reservoir for both radicals of HO and HO2 catalyzing the destruction of O3, the current study provides a comprehensive example of how acidic and basic catalysts assisted the gas-phase reactions.

Efficient synthesis of highly dispersed ultrafine Pd nanoparticles on a porous organic polymer for hydrogenation of CO2 to formate.

Precise design of catalytic supports is an encouraging technique for simultaneously improving the activity and stability of the catalyst. However, development of efficient heterogeneous catalysts for transforming CO2 into formic acid (FA) is still a big challenge. Herein, we report that Pd nanoparticles (NPs) based on a porous organic polymeric support containing amide and pyridine functional groups (AP-POP) can be an efficient catalyst for selective hydrogenation of CO2 to form formate with high efficiency even under mild reaction conditions (6.0 MPa, 80 °C). Electron density of the active Pd species modulated via the interaction between pyridine nitrogen and Pd play important roles in dramatic enhancement of catalytic activity and was indicated by X-ray photoelectron spectroscopy (XPS) along with CO chemisorption. This work provides an interesting and effective strategy for precise support design to improve the catalytic performance of nanoparticles.

Catalytic effect of (H2O) n (n = 1-3) clusters on the HO2 + SO2 → HOSO + 3O2 reaction under tropospheric conditions.

The HO2 + SO2 → HOSO + 3O2 reaction, both without a catalyst and with (H2O) n (n = 1-3) as a catalyst, has been investigated using CCSD(T)/CBS//M06-2X/aug-cc-pVTZ methods, and canonical variational transition state theory with small curvature tunneling (CVT/SCT). The calculated results show that H2O exerts the strongest catalytic role in the hydrogen atom transfer processes of HO2 + SO2 → HOSO + 3O2 as compared with (H2O)2 and (H2O)3. In the atmosphere at 0 km altitude within the temperature range of 280.0-320.0 K, the reaction with H2O is dominant, compared with the reaction without a catalyst, with an effective rate constant 2-3 orders of magnitude larger. In addition, at 0 km, it is worth mentioning that the relevance of the HO2 + SO2 → HOSO + 3O2 reaction with H2O depends heavily on its ability to compete with the primary loss mechanism of HO2 radicals (such as the HO2 + HO2 and HO2 + NO3 reactions) and SO2 (such as the SO2 + HO reaction). The calculated results show that the HO2 + SO2 → HOSO + 3O2 reaction with H2O cannot be neglected in the primary loss mechanism of the HO2 radical and SO2. The calculated results also show that for the formation of HOSO and 3O2, the contribution of H2O decreases from 99.98% to 27.27% with an increase in altitude from 0 km to 15 km, due to the lower relative concentration of water. With the altitude increase, the HO2 + SO2 → HOSO + 3O2 reaction with H2O cannot compete with the primary loss mechanism of HO2 radicals. The present results provide new insight into (H2O) n (n = 1-3) catalysts, showing that they not only affect energy barriers, but also have an influence on loss mechanisms. The present findings should have broad implications in computational chemistry and atmospheric chemistry.

Properties of magnetic carbon nanomaterials and application in removal organic dyes.

Magnetic carbon nanomaterials were prepared facilely by one step hydrothermal synthesis method using biologically regenerated glucose as carbon sources and ferric ammonium citrate as iron sources. As-synthesized nanomaterials were characterized by means of SEM, TEM, XRD, N2 adsorption-desorption, VSM and XPS etc. techniques. Results show as-prepared magnetic nanomaterials are sphere particles with aggregation state and magnetic α-Fe particles are enclosed by carbon matrixes. With increase of calcination temperature, the degrees of the sample aggregation decrease, whereas the average particle sizes, BET specific surface areas and saturation magnetizations increase. The carbon with graphite structure has higher adsorption efficiency than that of amorphous carbon for organic dye rhodamine B in water. Whereas the iron with amorphous structure shows higher photocatalytic activity than that of the iron with crystalline structure for the degradation of rhodamine B. And rhodamine B in water can almost be degraded completely through the combination of adsorption and photocatalysis.

Palladium on Nitrogen-Doped Mesoporous Carbon: A Bifunctional Catalyst for Formate-Based, Carbon-Neutral Hydrogen Storage.

The lack of safe, efficient, and economical hydrogen storage technologies is a hindrance to the realization of the hydrogen economy. Reported herein is a reversible formate-based carbon-neutral hydrogen storage system that is established over a novel catalyst comprising palladium nanoparticles supported on nitrogen-doped mesoporous carbon. The support was fabricated by a hard template method and nitridated under a flow of ammonia. Detailed analyses demonstrate that this bicarbonate/formate redox equilibrium is promoted by the cooperative role of the doped nitrogen functionalities and the well-dispersed, electron-enriched palladium nanoparticles.