相转移催化氟化合成3-氯-4-氟硝基苯的研究

概括了3氯4氟硝基苯的合成方法,采用正交实验法对3氯4氟硝基苯合成方法中的关键工序氟化工艺进行研究,获得了相转移催化剂作用下较佳的氟化反应工艺参数,并介绍了其在药物合成上的一些应用。     

Fluorination of CN x Nanotubes

Abstract

Multiwall CN _x nanotubes have been prepared by thermal decomposition of acetonitrile over Co/Ni catalytic particles. The fluorination of nanotubes was performed at room temperature by using a gaseous mixture of BrF₃ and Br₂. Transmission electron microscopy (TEM) and x‐ray diffraction (XRD) indicated that only the outer shells of CN _x nanotubes were fluorinated, whereas the inner shells remained intact. X‐ray photoelectron spectroscopy (XPS) showed an oxidation of pyridinic‐type nitrogen with tube fluorination.     

VUV Enhanced XeF2 Fluorination of Polymer Surfaces

Abstract

Exposure of polyethylene and polystyrene to xenon difluoride (XeF₂) in the presence of vacuum ultraviolet (VUV) irradiation emitted from O₂,N₂, Ar, Kr and Xe electrical discharges gives rise to surface fluorination. The extent of reaction is found to be governed by the synergistic effect between the VUV absorption characteristics of the XeF₂ feed gas and the polymer substrate. Polystyrene in combination with krypton electrical discharge emission lines yields the most fluorinated surface.     

Fast reactions with nano- and micrometer aluminum: A study on oxidation versus fluorination

The use of fluorine as an oxidizing agent in aluminum (Al)-based thermite reactions yields higher peak pressures and an increase in gas production compared with oxygen-containing oxidizers, such as molybdenum trioxide (MoO₃). Thus fluorination reactions have the potential to excel in situations that require high pressures and flame speeds. This study compares the combustion behaviors of Al/Teflon, Al/MoO₃/Teflon, and Al/MoO₃ in an effort to determine the effects that the replacement of oxygen with fluorine has on the reaction dynamics in both open and confined burning configurations. Data were collected from pressure sensors and high-speed imaging. The mass percent of Al was varied from 10 to 90% to study the effects of composition. The composites were then further tested at the optimum stoichiometry using either 50 nm or 1-3 μm Al to examine the effect of Al particle size. The addition of Teflon in an open configuration hinders the reaction due to a loss of liberated gas. Confining the reaction enables the trapped gases to enhance convection, yielding increased flame speeds. For confined conditions, the reactions containing Teflon exhibit higher peak pressures but lower flame speeds than the reactions with MoO₃. These results imply that a direct relationship between generated gas pressures and flame speeds does not generally exist when comparing different oxidizers. The theoretically predicted relationship for the relative flame speed versus relative particle size based on the melt-dispersion mechanism agrees with experimental data for all Al particle sizes and for the fluorination reaction. Particle synthesis parameters are suggested that could be controlled to enable micrometer-scale Al particles to achieve the performance of nanoscale Al particles. This is of significant practical importance, because nanoparticles are 30 to 50 times more expensive than the micrometer particles.     

Synthesis and characterization of a wide bandgap polymer based on a weak donor-weak acceptor structure for dual applications in organic solar cells and organic photodetectors

We synthesized a novel wide bandgap polymer, PDTFBT, forming a weak donor (WD)-weak acceptor (WA) structure for use in organic photodetectors (OPDs) and organic solar cells (OSCs). The fluorination in the D unit and the alkoxy substitution in the A unit induced WD and WA properties, respectively. The WD-WA structure of PDTFBT effectively broadened the bandgap compared to typical D-A structures, and the S-F and S-O dipole-dipole interactions induces a highly planar backbone structure with excellent π-π stacking in the vertical direction. In OPDs, conformationally less disordered PDTFBT polymer retained the constant responsivity and significantly improved the detectivity of PDTFBT:PC₇₁BM devices even with a thick active layer of 470 nm, contrary to the variation in the responsivity of P3HT:PC₆₁BM devices depending on the thickness. In OSCs, the deep HOMO energy level (−5.57 eV) of PDTFBT led to high Voc of 0.92 V in PDTFBT:PC₇₁BM devices, which was 0.3 eV higher than that of P3HT:PC₆₁BM devices (0.62 V), resulting in 1.8-fold enhanced power conversion efficiency. We demonstrated that the WD-WA structure with S-F and S-O interactions is highly promising strategy to make wide bandgap polymers for organic photodetectors and for the bottom cell of tandem architecture.     

Synthesis and characterization of fluorinated polybenzoxazine material with low dielectric constant

It is well-known that low dielectric materials are used as insulating materials, and the incorporation of fluorinated substitutes into polymer is able to decrease its dielectric constant because of small dipole and the low polarizability of the C–F bond. In this study, a novel structure of the fluorinated benzoxazine (F-1 benzoxazine) has been synthesized by incorporating the trifluoromethyl groups into the monomer, and its structure has also been characterized by ¹H NMR, ¹⁹F NMR and FT-IR. Further, we have prepared the fluorinated copolybenzoxazine (B-a/F-1=1/1) with substantially reduced dielectric constant at K=2.36. In addition, this fluorinated copolybenzoxazine possesses high glass transition temperature and high thermal stability, which is suitable for high temperature operation for certain special processes of interlayer dielectrics.     

Effect of the fluorine-addition order on the hydrodesulfurization activity of fluorinated NiW/Al2O3 catalysts

Fluorinated NiW/Al₂O₃ catalysts with different orders of fluorine addition have been prepared, tested for hydrodesulfurization (HDS) of thiophene, and characterized using nitric oxide chemisorption and temperature-programmed sulfidation. The catalyst surface area has been affected by fluorine addition but not by the order of fluorination. The fluorine addition-order does not affect the amount of fluorine retained in the catalysts after the calcination and the reaction steps, either. On the other hand, the order of fluorine addition changes the dispersion of the nickel and the tungsten species, incorporation of nickel with the tungsten edge sites, and consequently the HDS activity of the catalysts. The catalyst fluorinated in the last step, i.e., after addition of both tungsten and nickel, shows the highest activity in thiophene HDS, which is supported by other experimental results indicating the most nitric oxide chemisorption and the largest incorporation of nickel with the tungsten species. Accordingly, enhancement of the catalyst activity by fluorination is due to the repartition of the metal species rather than to partial solubilization of alumina in the fluorine-addition step.     

Synthesis of Ti3C2Fx MXene with controllable fluorination by electrochemical etching for lithium-ion batteries applications

Ti₃C₂T_x MXene has attracted remarkable attention due to its promising applications in energy storage and sensors. However, traditional MXene preparation methods used HF as etchant, which was highly toxic and harmful to human and environment. Moreover, the aqueous etchants will also result in the combination of OH, O and F groups on the surfaces, making it difficult to control the varieties and contents of the surface terminations. In this paper, a green and mild electrochemical exfoliation method was proposed to synthesize Ti₃C₂F_x and synchronously control its fluorination degree on the surface. A non-aqueous ionic liquid, [BMIM][PF₆]-based solution was used as electrolyte. The as-prepared Ti₃C₂F_x was fluorinated with the CF and TiF₃ groups, which were electrochemically active and contributed to the excellent cycling stability of the MXene anode-based Li-ion batteries. These findings provided a facile strategy to prepare MXene materials and dope MXene with tailored property for MXene-based energy devices applications.     

Fluorine functionalized asymmetric indo [2,3-b]quinoxaline framework based D-A copolymer for fullerene polymer solar cells

Innovating molecular structure of copolymer donor materials is still one of the prominent approach to obtain high-performance polymer solar cells (PSCs). In this paper, two novel wide bandgap (WBG) copolymers, namely PBDTTS-IQ and PBDTTS-DFIQ, based on asymmetric planar aromatic core indo [( Li et al., 2012; Wang et al., 2020) 2,32,3-b]quinoxaline (IQ) as acceptor unit through tuning side chains with fluorine (F) atom engineering and exemplary alkylthio-thienyl substituted benzodithiophene (BDTTS) donor group, are synthesized and finally employed as the photovoltaic donor materials for fullerene polymer solar cells (PSCs). After blending with PC₇₁BM acceptor, the PBDTTS-DFIQ:PC₇₁BM blend film presented better efficient exciton dissociation and charge extraction, more balanced electron/hole mobility (μ_h/μ_e), and nice morphology in comparison with PBDTTS-IQ:PC₇₁BM blend film. Encouragingly, the PBDTTS-DFIQ:PC₇₁BM based PSCs exhibits a higher power conversion efficiency (PCE) of 7.4% than that of the device based on the PBDTTS-IQ:PC₇₁BM blend with a PCE of 4.96%, which thanks to an enhancement of open-circuit voltage (V_oc) of 0.84 V, short current density (J_sc) of 13.26 mA cm⁻² and fill factor (FF) of 66.00% simultaneously. These results demonstrate that this asymmetric IQ framework is a wonderful acceptor moiety to build light-harvesting copolymers for highly efficient PSCs.     

Insights into the influence of fluorination positions on polymer donor materials on photovoltaic performance

To explore the influence of fluoro substitution position and number on optical, electrochemical and photovoltaic properties, three novel donor-acceptor (D-A) alternative copolymers (PHF, PFH and PFF) were synthesized by Stille polycondensation of 2,3-diphenyl-5,8-di(thiophen-2-yl)quinoxaline (DTQx) acceptor unit and indacenodithiophene (IDT) donor unit. As films, PHF and PFF comprising two fluoro substituents on the lateral phenyl groups displayed a broad absorption ranging from 350 to 700 nm; whereas PFH containing two fluorine atoms on the polymer main chain exhibited a slightly narrower absorption ranging from 350 to 650 nm. In addition, fluoro substitution on the polymer main chain can lower the HOMO level of the resulted polymers. As expected, PFH and PFF possess deeper HOMO energy level than PHF. Polymer solar cells (PSCs) were fabricated with these three polymers as donor materials and PC₇₁BM as acceptor material. PHF based PSCs gave a power conversion efficiency (PCE) of 7.2% with a V_oc of 0.84 V, a J_sc of 12.46 mA/cm² and an FF of 0.69. And PFH based PSCs showed a PCE of 6.19% with a V_oc of 0.93 V, a J_sc of 9.57 mA/cm² and an FF 0.70. However, a PCE of only 2.9% with a V_oc of 0.92 V, a J_sc of 4.61 mA/cm² and an FF of 0.68 was obtained for PFF based PSCs. Transmission electron microscopy (TEM) and resonant soft X-ray scattering (R-SoXS) studies indicated that the introduction of four fluorine atoms at each repeating unit can spoil the morphology of active layer. These results highlight the importance of fluorination position and number to the performance of PSCs.