Fluorine Precursor Research Articles

N-Heterocycle-Substituted Hexa-peri-hexabenzocoronenes with Windmill Architectures.

We describe the synthesis and computational investigation of N-heterocycle-substituted hexa-peri-hexabenzocoronenes (HBCs). Following our method for the preparation of thioether-substituted HBCs, we prepared pyrrole-, indole-, carbazole-, and 1H-benz[g]indole-substituted HBCs from the corresponding fluorinated precursors under microwave irradiation. A series of polysubstituted benzoindole-HBCs with windmill architectures was also synthesized using the polyfluorinated HBC analogs. Due to the circular arrangement of the benzoindole moiety, the attachment of multiple substituents results in the presence of multiple conformers at room temperature. The rotation barrier can be overcome by heating the compounds to 323-333 K. Additionally, the investigation of the relaxed geometries shows two π-stacking motifs within the conformers. Similar to the thioether substituted HBCs, the nature of the heterocycle does not influence the optoelectronic properties of the HBC core. The attachment of multiple benzoindole substituents leads to a bathochromic shift of the absorption and emission spectra, comparable to our previous studies.

Exploring Gas‐Solid Phase Diagrams: Novel Methods for Oxyfluorination of Mn3O4 and Mn2O3 with Molecular Fluorine

AbstractFluorinated, manganese‐redox cation‐disordered rocksalts are promising candidates for high‐performance cobalt‐free Li‐ion cathode active material. A need for reactive fluorinated precursors was however identified. While manganese oxyfluorides are promising precursor candidates, none stable at room temperature was reported prior to 2023. The key to their recent synthesis by reacting molecular fluorine with MnO was a procedure to continuously scan the temperature axis in search of activation temperatures. In line with this philosophy of continuous exploration of the chemical space, two experimental procedures are reported to scan the stoichiometry axis of a gas‐solid phase diagram in search of transitions and intermediate compounds. Their application to F2 ‐ Mn3O4 and F2 ‐ Mn2O3 phase diagrams resulted in the discovery of two new ranges of stable manganese oxyfluorides of respective compositions MnO1.33‐0.13xFx with x<0.5 and MnO1.5‐0.22xFx with x<1.

Tuning electronic structure of metal-free dual-site catalyst enables exclusive singlet oxygen production and in-situ utilization

Developing eco-friendly catalysts for effective water purification with minimal oxidant use is imperative. Herein, we present a metal-free and nitrogen/fluorine dual-site catalyst, enhancing the selectivity and utilization of singlet oxygen (1O2) for water decontamination. Advanced theoretical simulations reveal that synergistic fluorine-nitrogen interactions modulate electron distribution and polarization, creating asymmetric surface electron configurations and electron-deficient nitrogen vacancies. These properties trigger the selective generation of 1O2 from peroxymonosulfate (PMS) and improve the utilization of neighboring reactive oxygen species, facilitated by contaminant enrichment at the fluorine-carbon Lewis-acid adsorption sites. Utilizing these insights, we synthesize the catalyst through montmorillonite (MMT)-assisted pyrolysis (NFC/M). This method leverages the role of MMT as an in-situ layer-stacked template, enabling controlled decomposition of carbon, nitrogen, and fluorine precursors and resulting in a catalyst with enhanced structural adaptability, reactive site accessibility, and mass-transfer capacity. The NFC/M demonstrates an impressive 290.5-fold increase in phenol degradation efficiency than the single-site analogs, outperforming most of metal-based catalysts. This work not only underscores the potential of precise electronic and structural manipulations in catalyst design but also advances the development of efficient and sustainable solutions for water purification.

Are Geotextiles Silent Contributors of Ultrashort Chain PFASs to the Environment?

We investigated the presence of per- and poly fluoroalkyl substances (PFASs) in woven and nonwoven polypropylene geotextiles and four nonwoven polyester geotextiles commonly used in modern geosynthetic composite lining systems for waste containment facilities such as landfills. Targeted analysis for 23 environmentally significant PFAS molecules and methods for examining "PFAS total" concentrations were utilized to assess their occurrence in geotextiles. This analysis showed that most geotextile specimens evaluated in the current investigation contained the ultrashort chain PFAS compound pentafluoropropionic acid (PFPrA). While the concentrations ranged from nondetectable to 10.84 μg/g, the average measured concentrations of PFPrA were higher in polypropylene than in polyester geotextiles. "PFAS total" parameters comprising total fluorine (TF) and total oxidizable precursors (TOPs) indicate that no significant precursor mass nor untargeted intermediates were present in geotextiles. Therefore, this study identified geotextiles as a possible source of ultrashort PFASs in engineered lined waste containment facilities, which may contribute to the overall PFAS total concentrations in leachates or liquors they are in contact with. The findings reported for the first time herein may lead to further implications on the fate and migration of PFASs in geosynthetic composite liners, as previously unidentified concentrations, particularly of ultrashort-chain PFASs, may impact the extent of PFAS migration through and attenuation by constituents of geosynthetic composite liner systems. Given the widespread use of geotextiles in various engineering activities, these findings may have other unknown impacts. The significance of these findings needs to be further elucidated by more extensive studies with larger geotextile sample sizes to allow broader, generalized conclusions to be drawn.

Intimately mixed copper, cobalt, and iron fluorides resulting from the insertion of fluorine into a LDH template.

The advancement of lithium-ion batteries (LIBs) with high performance is crucial across various sectors, notably in space exploration. This advancement hinges on the development of innovative cathode materials. Our research is dedicated to pioneering a new category of cathodes using fluorinated multimetallic materials, with a specific focus on diverging from the traditional Ni, Co, and Mn-based NMC chemistries by substituting nickel and manganese with copper and iron which are more sustainable elements. Our goal is also to enhance the robustness of cathodes upon cycling by substituting oxygen with fluorine as the metal-ligand. To achieve this, an intimate composite blend of CuF2 and FeF3, through the multi-metallic template fluorination (MMTF) methodology using a layered double hydroxide (LDH) as a precursor has been designed. Each of these components was carefully selected for its distinct attributes, including high redox potential, elevated energy density, substantial theoretical capacity, and improved cyclability. The composition denoted as (Cu1.5Co0.5)2+(Fe0.75Al0.25)3+ has been selected for fluorination because it maximizes Fe3+ and Cu2+ amount in the screened LDHs. Subsequently, this particular LDH was fluorinated through solid-gas fluorination at different temperatures (200, 350, and 500 °C) using gaseous molecular fluorine (F2). A comprehensive characterization of these materials using various techniques, including X-ray diffraction (XRD), 57Fe Mössbauer spectrometry, scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX), and inductively coupled plasma analyses (ICP-AES) was conducted, and the evolution of LDH upon fluorination has revealed an intermediate porous texture particularly sensitive to hydration. Two original crystallographic phases are else obtained by fluorination: one formed by the hydration of the amorphous intermediate compound: Cu3Fe1.5Al0.5F12(H2O)12 an anti-perovskite structure and another stabilized through the combination of solid gas fluorination and LDH precursor yielding an original CoFeF5-type phase. Raman operando during cyclic voltammetry measurement applied on a sample fluorinated at 500 °C and used as a cathode in front of lithium metal was finally conducted to validate redox activity and mechanism.

Deciphering the influence of fluorine on the electrochemical performance of MAX and derived MXene by selective electrophilic fluorination

The emerging class of MAX phases and corresponding MXenes offers a unique advantage of tunable surface functionalities, such as -O, -OH, and -F, which endow them with excellent electrochemical activity. This study focuses on the fluorination of the MAX phases and corresponding MXenes using an electrophilic fluorinating agent, Selectfluor (SF). The fluorination process was carried out to selectively fluorinate the MAX phase while minimizing etching effects, showcasing the distinct role of the electrophilic fluorine precursor over the conventional nucleophilic fluorinating agents. Intriguingly, the fluorinated MAX phase, with a fluorine content of 3.21 at%, demonstrated significantly enhanced electrochemical performance, exhibiting a two-fold increase in the specific capacitance compared to pristine MAX. Moreover, selective fluorination is further extended to MXene derivatives prepared through the conventional route. Using SF, we facilitated electrolyte-ion transport through the functionalized surface, resulting in an enhancement of ∼1400% in energy storage capacity after the fluorination of MXene. The observed improvement in the electrochemical performance can be attributed to the formation of electrochemically active Ti-F and C-F moieties at the surface as opposed to surface hydroxyls and oxidized MXene. The high electronegativity of fluorine atoms contributes to fast ion diffusion at the electrode surface, enhancing wettability and leading to superior electrochemical performance. As a result, our work introduces a novel and simple solution-based methodology for selectively fluorinating MAX phases and their MXene derivatives, unlocking their potential for enhanced electrochemical applications. This methodology can be extended to various MAX phases and their derivatives, offering precise control over the surface moieties in electrochemical systems where fine-tuning is essential for optimal performance. Overall, this study significantly contributes to advancing the understanding and utilization of fluorinated MAX and MXene materials in electrochemical energy storage and beyond.

Occurrence of quantifiable and semi-quantifiable poly- and perfluoroalkyl substances in united states wastewater treatment plants

Both quantifiable and semi-quantifiable poly- and perfluoroalkyl substances (PFAS) were evaluated in the influent, effluent, and biosolids of 38 wastewater treatment plants. PFAS were detected in all streams at all facilities. For the means of the sums of detected, quantifiable PFAS concentrations were 98 ± 28 ng/L, 80 ± 24 ng/L, and 160,000 ± 46,000 ng/kg (dry weight basis) in the influent, effluent, and biosolids (respectively). In the aqueous influent and effluent streams this quantifiable PFAS mass was typically associated with perfluoroalkyl acids (PFAAs). In contrast, quantifiable PFAS in the biosolids were primarily polyfluoroalkyl substances that potentially serve as precursors to the more recalcitrant PFAAs. Results of the total oxidizable precursor (TOP) assay on select influent and effluent samples showed that semi-quantified (or, unidentified) precursors accounted for a substantial portion (21 to 88%) of the fluorine mass compared to that associated with quantified PFAS, and that this fluorine precursor mass was not appreciably transformed to perfluoroalkyl acids within the WWTPs, as influent and effluent precursor concentrations via the TOP assay were statistically identical. Evaluation of semi-quantified PFAS, consistent with results of the TOP assay, showed the presence of several classes of precursors in the influent, effluent, and biosolids; perfluorophosphonic acids (PFPAs) and fluorotelomer phosphate diesters (di-PAPs) occurred in 100 and 92% of biosolid samples, respectively. Analysis of mass flows showed that, for both quantified (on a fluorine mass basis) and semi-quantified PFAS, the majority of PFAS exited WWTPs through the aqueous effluent compared to the biosolids stream. Overall, these results highlight the importance of semi-quantified PFAS precursors in WWTPs, and the need to further understand the impacts of their ultimate fate in the environment.

Plasma-enhanced fluorination of layered carbon precursors for high-performance CFx cathode materials

Lithium/fluorinated carbon (Li/CFx) primary batteries employed in commercial, medical, and military fields, are still hindered by the poor rate performance, which is closely related to the fluorination process and precursor carbon materials. Herein, we reported an eco-friendly, simple and efficient fluorination strategy, namely, plasma-enhanced fluorination (PEF), to manufacture plasma fluorinated expanded graphite (PFEG) and plasma fluorinated graphene (PFG). Chemically similar PFEG and PFG materials were also constructed to study the effect of morphology and microstructure of the carbon precursors on the PEF process and the resulting CFx materials’ electrochemical performance. The Li/PFG coin cell exhibits excellent rate performance with a high specific capacity of 838.3 mAh/g at a high current density of 10 A/g. The pouch cell based on the PEF pilot reactor delivers a specific capacity 771.4 mAh/g at 0.1 A/g, confirming the potential of PEF for scalable production of high-quality (high energy density and high-power density) CFx cathode materials. These findings will greatly contribute to the research and development of Li/CFx primary batteries in the way of optimizing carbon precursors and developing new fluorination strategies.

Biological and Chemical Transformation of the Six-Carbon Polyfluoroalkyl Substance N-Dimethyl Ammonio Propyl Perfluorohexane Sulfonamide (AmPr-FHxSA).

Sites impacted by aqueous film-forming foam (AFFF) contain co-contaminants that can stimulate biotransformation of polyfluoroalkyl substances. Here, we compare how microbial enrichments from AFFF-impacted soil amended with diethyl glycol monobutyl ether (found in AFFF), aromatic hydrocarbons (present in co-released fuels), acetate, and methane (substrates used or formed during bioremediation) impact the aerobic biotransformation of an AFFF-derived six-carbon electrochemical fluorination (ECF) precursor N-dimethyl ammonio propyl perfluorohexane sulfonamide (AmPr-FHxSA). We found that methane- and acetate-oxidizing cultures resulted in the highest yields of identifiable products (38 and 30%, respectively), including perfluorohexane sulfonamide (FHxSA) and perfluorohexane sulfonic acid (PFHxS). Using these data, we propose and detail a transformation pathway. Additionally, we examined chemical oxidation products of AmPr-FHxSA and FHxSA to provide insights on remediation strategies for AmPr-FHxSA. We demonstrate mineralization of these compounds using the sulfate radical and test their transformation during the total oxidizable precursor (TOP) assay. While perfluorohexanoic acid accounted for over 95% of the products formed, we demonstrate here for the first time two ECF-based precursors, AmPr-FHxSA and FHxSA, that produce PFHxS during the TOP assay. These findings have implications for monitoring poly- and perfluoroalkyl substances during site remediation and application of the TOP assay at sites impacted by ECF-based precursors.

EPA's detection methods, the drinking water treatability database, and innovative technologies for PFAS remediation

AbstractPer‐ and polyfluoroalkyl substances (PFAS) are a large group of highly fluorinated, aliphatic chemicals detected throughout the environment, including in human serum. Several regulatory milestones have been achieved in the United States for these environmentally toxic chemicals linked to health problems in humans, the latest one being the US Environmental Protection Agency's (EPA's) PFAS Strategic Roadmap necessitating detection and remediation of PFAS. This article, in addition to briefly discussing these regulatory milestones, evaluates the EPA's detection methods for PFAS including EPA Methods 533, 537.1, and 8327 and other methods currently under development such as the total organic fluorine (TOF) and total organic precursor (TOP) methods. The article also mentions the methods used by other federal agencies for PFAS quantitation. The EPA's drinking water treatability database (TDB) is also described along with the advantages and challenges of the effective treatment methods for PFAS. Most of these treatment methods in the EPA's drinking water TDB face the challenge of disposing wastes containing PFAS, an issue not faced by innovative technologies, and some of these innovative technologies are also discussed. This article will help to understand the current status on the detection and remediation technologies for PFAS treatment in soil and water. It is imperative to have these technologies ready to assist with the remediation objectives in the PFAS Strategic Roadmap.

Design, Synthesis, and Applications of ortho -Sulfur Substituted Arylphosphanes

Design, Synthesis, and Applications of <i>ortho</i> -Sulfur Substituted Arylphosphanes

Ultra-Short-Chain PFASs in the Sources of German Drinking Water: Prevalent, Overlooked, Difficult to Remove, and Unregulated.

Per- and polyfluoroalkyl substances (PFASs) have been a focal point of environmental chemistry and chemical regulation in recent years, culminating in a shift from individual PFAS regulation toward a PFAS group regulatory approach in Europe. PFASs are a highly diverse group of substances, and knowledge about this group is still scarce beyond the well-studied, legacy long-chain, and short-chain perfluorocarboxylates (PFCAs) and perfluorosulfonates (PFSAs). Herein, quantitative and semiquantitative data for 43 legacy short-chain and ultra-short-chain PFASs (≤2 perfluorocarbon atoms for PFCAs, ≤3 for PFSAs and other PFASs) in 46 water samples collected from 13 different sources of German drinking water are presented. The PFASs considered include novel compounds like hexafluoroisopropanol, bis(trifluoromethylsulfonyl)imide, and tris(pentafluoroethyl)trifluorophosphate. The ultra-short-chain PFASs trifluoroacetate, perfluoropropanoate, and trifluoromethanesulfonate were ubiquitous and present at the highest concentrations (98% of sum target PFAS concentrations). "PFAS total" parameters like the adsorbable organic fluorine (AOF) and total oxidizable precursor (TOP) assay were found to provide only an incomplete picture of PFAS contamination in these water samples by not capturing these highly prevalent ultra-short-chain PFASs. These ultra-short-chain PFASs represent a major challenge for drinking water production and show that regulation in the form of preventive measures is required to manage them.

Two birds with one stone: large catalytic areas and abundant nitrogen sites inspired by fluorine doping contributing to CO2RR activity and selectivity.

Electroreduction of CO2 based on metal-free carbon catalysts is an attractive approach for useful products. However, it remains a great chemical challenge due to its unsatisfactory activity and poor selectivity. Here, we report a successful case to greatly improve CO2-to-CO conversion on carbon black (CB) and nitrogen-doped carbon black (N-CB). By introducing fluorine, the faradaic efficiency of CO was increased from 12.8% (CB) and 50.8% (N-CB) to 93.1% (nitrogen and fluorine co-doped carbon black, N,F-CB) at -0.7 V. A partial current density of 4.19 mA cm-2 remained durable for about 23 h. The superiority of N,F-CB can be attributed to its large catalytic areas and abundant N active sites inspired by fluorine doping. Specifically, the fluorine precursor of polyvinylidene fluoride (PVDF) firstly performs as a nitrogen fixator, protecting the catalyst from more nitrogen escaping during the carbonization treatment. The number of nitrogen sites is about 4.4 times higher than it is for the N-CB. Meanwhile, PVDF as the area extender significantly improves the catalytic area; the specific surface area and the ECSA of N,F-CB are 8.7 and 6.9 times higher than that of CB. This work provides an insight into how heteroatoms can manipulate catalytic activity and selectivity through the catalytic area of carbon materials with more active sites.

Atomic layer deposition of hafnium and zirconium oxyfluoride thin films

Hafnium and zirconium oxyfluoride films may act as effective protective coatings during plasma processing. The low molar volume expansion/contraction ratios and the small estimated strain values versus fluorination/oxidation suggest that hafnium and zirconium oxyfluorides can serve as protective coatings in both fluorine and oxygen plasma environments. To demonstrate the procedures for depositing these films, hafnium and zirconium oxyfluorides with tunable stoichiometry were grown using atomic layer deposition (ALD) at 150 °C. Tetrakis(dimethylamido)hafnium and tetrakis(ethylmethylamido)zirconium were used as the metal precursors. H2O and HF were employed as the oxygen and fluorine precursors, respectively. MOxFy (M = Hf and Zr) films were grown using two deposition mechanisms: the nanolaminate method and the HF exchange method. In situ quartz crystal microbalance studies were employed to monitor the MOxFy growth. Both deposition methods observed a linear MOxFy growth at 150 °C. The nanolaminate method is defined by the sequential deposition of MOx ALD and MFy ALD layers. Compositional tunability was achieved by varying the ratio of the number of MOx ALD cycles to the number of MFy ALD cycles in the nanolaminate. The HF exchange method is based on the thermodynamically favorable fluorination reaction of MOx by HF. Variable oxygen-to-fluorine concentrations in these films were obtained either by changing the HF pressure or by varying the thickness of the underlying MOx ALD layers. Ex situ Rutherford backscattering spectroscopy measurements were utilized to determine the composition of the various MOxFy thin films. Both deposition techniques displayed a wide range of compositional tunability from HfO2 to HfF4 and ZrO2 to ZrF4. In addition, the physical sputtering rates of MOxFy films were estimated from the film removal rates during ex situ x-ray photoelectron spectroscopy depth profiling. The physical sputtering rates increased with F concentration in the MOxFy films.

A strategy for preparing controllable, superhydrophobic, strongly sticky surfaces using SiO2@PVDF raspberry core-shell particles.

In nature, wetting by water droplets on superhydrophobic materials is governed by the Cassie–Baxter or Wenzel models. Moreover, sticky properties, derived from these types of wettings, are required for a wide range of applications involving superhydrophobic materials. As a facile new strategy, a method employing a gaseous fluorine precursor to fabricate core–shell particles, comprising perfectly shaped fluorine shells with adjustable adhesive strength, is described in this paper. Silica was used as the hydrophilic core, while polyvinylidene fluoride (PVDF) was used for the hydrophobic shell coating, forming a raspberry-like shape. In addition, controlling the amount of PVDF coated on the silica surface enabled the water droplets to come into contact with both the PVDF of the shell and the silica of the core, thereby controlling both the superhydrophobicity and the adhesive strength. Thus, the synthesized particles formed a structured coating with controllable stickiness and contact angles of 131–165°. Furthermore, on surfaces with high adhesivity, the water droplets remained stable at tilt angles of 90° and 180° even under a strong centrifugal force, whereas on surfaces with low adhesivity, the water droplets slid off when the substrate was tilted at 4°.

Optimization of the Synthesis of 18F‐D2‐Deprenyl With Mild 18F‐Fluorination and Minimum Precursor Input for PET Imaging of Neuroinflammation

Here, we established optimized conditions for a mild 18F‐fluorination to yield 18F‐deprenyl and 18F‐D2‐deprenyl as neuroinflammation imaging agents by fully automatic synthesis. Initially, manual synthesis with 1 mg of precursor and pH = 7.8 KOMs elution buffer yielded 85–92% of 18F‐incorporation yields and showed nondecay corrected yields of 15–17%. Fully automatic synthesis showed a nondecay corrected radiochemical yield of 10.7 ± 0.46%. Owing to low precursor input, the maximum molar activity achieved was 1302.4 ± 26.4 GBq/μmol. Our mild 18F‐fluorination procedure showed higher radiochemical yields and molar activity than those by previously used procedures, even with minimized precursor input.

Reverse microemulsion synthesis of mixed α and β phase NaYF4:Yb,Er nanoparticles: calcination induced phase formation, morphology, and upconversion emission

A novel “water-in-oil” type reverse microemulsion assisted synthesis detail on the formation of mixed cubic and hexagonal (α + β) phase NaYF4:Yb,Er nanoparticles and their upconversion emission properties are presented. The effect of surfactants, fluorine precursors on the crystallographic phase fraction, crystallite size of NaYF4:Yb,Er nanoparticles on red upconversion emission is discussed. The NaYF4:Yb,Er nanoparticles synthesized with CTAB, and oleic acid surfactants give larger crystallite size and moderate hexagonal/cubic phase fraction. It has resulted very intense upconversion red emission. The oleic-acid-free preparation of NaYF4:Yb,Er nanoparticles resulted highly-agglomerated nanoparticles and low crystallite size, which gives less-intense upconversion emission. The cubic and hexagonal phase fractions of NaYF4:Yb,Er depends on surfactants, microemulsion, molar concentrations of precursors, and post-calcination. All these factors influence the mondispersibility and upconversion red emission properties. The 980 nm laser pump power dependent upconversion emission studies have confirmed the typical two-photon behavior in α + β phase NaYF4:Yb,Er nanoparticles. Their decay life was also measured to correlate the upconversion red emission intensity. The effect of mixed α + β phase NaYF4:Yb,Er nanoparticles on the 1530 nm NIR emission is also presented.

Impact of Fluorination on Microstructures and Surface Properties of SiC Nanocomposites with Si x C y F z Composition.

Silicon carbide (SiC) is an effective catalyst for generating fuel from organics through gasification. SiC has shown promising results as a catalyst due to its extraordinary thermal and oxidation resistance abilities. Researchers are yet to identify an efficient silicon carbide composite material that enhances the desired quality of fuel/liquid production. The present study deals with in situ synthesis of fluorine-doped silicon carbide using agriculture waste. Biochar, a waste by-product from the gasification process, proved to be a potential carbon source for fabrication of silicon carbide nanowires (SiCNWs). Pristine SiCNWs exhibited nanospheres and freestanding nanowire (coiled, rods, bamboolike, or hexagonal prism) structures with transversal optical mode indexed to the β-phase (β-SiC). Fabrication of fluorine (F)-doped SiC from a silica–carbon–fluorine (SiOx/Cy/Fz) precursor resulted in uneven flat-surfaced silicon carbide materials accompanied by progressive pore blockage with increasing F-content. Pore blockage was confirmed by declining the surface area from 60.70 m2 g–1 of the lowest dopant to 17.33 m2 g–1 of the maximum dopant, compared to neat SiC (63.20 m2 g–1). Introduction of fluorine led to decreased silicon contents and collapsed nanowire while the carbon and oxygen contents increased.

Interpolymer Self-Assembly of Bottom-up Graphene Nanoribbons Fabricated from Fluorinated Precursors.

Interpolymer self-assembly of bottom-up graphene nanoribbons (GNRs) has been realized by using fluorinated anthracene trimer precursors (HFH-DBTA) deposited onto heated Au(111) substrate. Whereas polymers derived from conventional precursor [10,10'-dibromo-9,9'-bianthryl (DBBA)] are adsorbed on Au(111) without apparent close packing, poly-HFH polymers derived from HFH-DBTA are densely self-assembled and require a long annealing time for cyclo-dehydrogenation because of the steric hindrance. First-principles calculations based on density functional theory revealed that the partially fluorinated edges of HFH-DBTA make molecular-substrate interaction weaker than that of DBBA, accelerate desorption, and leave islands of accumulated and locally aligned polymers. The partially fluorinated precursors also induce templating effects in interpolymer stacking because of H-F hydrogen bonding and F-F repulsion. The statistical analysis revealed that 84% of GNRs is parallel to the adjacent GNRs in the case of HFH-DBTA precursors. Field-effect transistors (FETs) were fabricated using such locally aligned multiple GNRs as channels. It has been found that on average, the on-current of the FETs is three times larger than that of FETs using less-aligned GNR channels made from the conventional DBBA precursors.

Hierarchical Zr‐MTW Zeolites Doped with Copper as Catalysts of Ethanol Conversion into 1,3‐Butadiene

AbstractThe hierarchical Zr‐MTW zeolites are prepared using NH4F and HF as mineralizing agents and structure‐directed agent like Gemini‐type surfactant and studied by X‐ray diffraction (XRD), 29Si magic angle spinning nuclear magnetic resonance (29Si MAS NMR), Fourier transform infrared (FTIR) spectroscopy with pyridine, 2,6‐di‐tert‐butylpyridine and CD3CN as probe molecules. Structural characteristics and acid‐base properties of the zeolites depend on concentration of fluorine precursor in the reaction medium (a ratio of Si/F). The hierarchical Zr‐MTW zeolites (included doped with copper) have been tested in ethanol conversion into 1,3‐butadiene by Lebedev method. The symbatical dependence of 1,3‐butadiene productivity with the concentration of Lewis acidic sites determined by FTIR spectroscopy of adsorbed CD3CN is observed. 1.3‐Butadiene selectivity of 68 % with ethanol conversion of 81 % are achieved in the presence of Cu/Zr‐MTW catalyst.