多级孔芳香骨架材料的合成及固载硫脲催化剂的研究

合成了一种多级孔芳香骨架材料(PAF-70); 使用由氨基修饰过的单体, 应用该合成策略得到了同样具有窄分布介孔的含有氨基活性位点的PAF材料, 并通过硫脲单体与其氨基活性位点的反应, 将硫脲基团引入PAF-70材料中, 获得了含有硫脲催化位点的材料(PAF-70-thiourea). 氮气吸附-脱附测试结果显示, PAF-70存在孔径分布较窄的介孔, 介孔孔径为3.8 nm, 与模拟计算值(约3.7 nm)吻合. 热重分析结果表明, PAF-70具有很高的热稳定性. PAF-70在大多数溶剂中可以稳定存在, 具有良好的化学稳定性. 将PAF-70-thiourea作为催化剂, 应用在N-溴代琥珀酰亚胺(NBS)氧化醇类的反应中, 其表现出较高的催化活性、 较高的稳定性和广泛的底物适用性. 与含有相同硫脲催化位点的金属有机框架(MOF)材料(IRMOF-3-thiourea)作为催化剂对比, 进一步证实PAFs材料非常适合作为催化有机反应的固载平台.     

Carbohydrate-based nanostructured catalysts: applications in organic transformations

The requirement of green and sustainable materials to prepare heterogeneous catalysts has intensified for practical reasons over the past few decades. Carbohydrates are possibly the most plentiful and renewable organic materials in nature with inimitable physiochemical properties, plausible low-cost and large-scale production, and sustainability features could be exploited in the generation of nanostructured heterogeneous catalysts. This review article outlines the organic transformations catalyzed by diverse carbohydrate-based nanostructured catalysts in greener and environmentally friendly processes. Selected examples are highlighted for a variety of organic reactions exploiting the proposed catalysts’ reactivity and reusability, and interactions with the intrinsic nature of the applied carbohydrate supports; advantages and speculated challenges of the introduced catalysts are deliberated as well.     

Molecular design of ambipolar redox-active molecules II: closed-shell systems

This mini-review highlights key structural features that should be taken into account when creating ambipolar redox-active closed-shell metal-free molecules. This type of compound is strongly required for the fabrication of all-organic ‘poleless’ batteries and semiconductors. The suggested strategies aimed at stabilization of both oxidized (cationic) and reduced (anionic) redox-states are based on the comprehensive analysis of the most successful structures taken from the recent publications.     

The Role of Polarization in Photocatalysis

Semiconductor photocatalysis as a desirable technology shows great potential in environmental remediation and renewable energy generation, but its efficiency is severely restricted by the rapid recombination of charge carriers in the bulk phase and on the surface of photocatalysts. Polarization has emerged as one of the most effective strategies for addressing the above‐mentioned issues, thus effectively promoting photocatalysis. This review summarizes the recent advances on improvements of photocatalytic activity by polarization‐promoted bulk and surface charge separation. Highlighted is the recent progress in charge separation advanced by different types of polarization, such as macroscopic polarization, piezoelectric polarization, ferroelectric polarization, and surface polarization, and the related mechanisms. Finally, the strategies and challenges for polarization enhancement to further enhance charge separation and photocatalysis are discussed.     

Synthetic studies towards the penicisulfuranols: Synthesis of an advanced spirocyclic diketopiperazine intermediate

The 2,5-diketopiperazine (DKP) moiety is a core feature of many natural products and medicinally relevant scaffolds. As part of our efforts directed towards a total synthesis of penicisulfuranol B, we have developed and report herein: (1) the preparation of an N-hydroxy diketopiperazine intermediate accessible via a molybdenum-mediated oxidation of a parent diketopiperazine, and (2) further synthetic studies leading to a novel spirocyclic dihydrobenzofuran-containing diketopiperazine.     

Assessment of the beneficial combination of electrochemical and ultrasonic activation of compounds originating from biomass

The electro-oxidation of organic molecules at the anode with simultaneous generation of hydrogen at the cathode in electrosynthesis reactors is considered as a promising and efficient process for the co-production of hydrogen and bio-sourced value-added chemicals. In this study and for the first time, we investigated the electro-oxidation of glucose and methylglucoside in 0.1 mol L⁻¹ NaOH on polycrystalline Pt (real surface area = 14.5 ± 0.5 cm², roughness ≈ 5) in the potential range [0; +1.20 V vs. rhe] under silent and ultrasonic (bath, 45 kHz, P_acous = 11.20 W) conditions. A series of linear sweep voltammograms, chronoamperograms and high-performance liquid chronoamperograms were generated. It was found that higher current densities were obtained under ultrasonic conditions over the potential range of +0.25 V to +1.10 V vs. rhe, indicating that higher oxidation rates were provided under ultrasonication. It was observed that the desorption of species from the Pt surface in the medium potential region was favoured, allowing free catalytic Pt sites for further adsorption and oxidation of reactants; and in the high potential region, high peak current densities in the presence of ultrasound was due to enhanced mass transport of the electroactive species from the bulk electrolyte to the Pt-polycrystalline electrode surface. HPLC studies confirmed that higher electrochemical activity was obtained in the presence of ultrasound than in the absence. In our conditions, it was also found that low frequency ultrasound did not change the selectivity of the glucose and methylglucoside electro-oxidation reactions but instead, a significant increase in the rate of conversion was observed.     

Synthesis of Porphyrinquinone and Doubly‐Fused Diporphyrin Quinone Through Oxidation of Diarylporphyrins Using a Hypervalent Iodine Compound

Treatment of a meso‐diarylporphyrin with PhI(OAc)₂ in the presence of BF₃ ? OEt₂ and propionic acid affords the corresponding porphyrinquinone in a high yield (91%). A novel quinone derived from meso‐meso β–β doubly‐fused diporphyrin was obtained as the sole byproduct (16% yield), which exhibits strong panchromatic absorption between 300 and 1000 nm. It has a low HOMO‐LUMO gap owing to expanded and low‐symmetry π‐planes.     

Electrochemical Vicinal Difluorination of Alkenes: Scalable and Amenable to Electron-Rich Substrates

Fluorinated alkyl groups are important motifs in bioactive compounds, positively influencing pharmacokinetics, potency and conformation. The oxidative difluorination of alkenes represents an important strategy for their preparation, yet current methods are limited in their alkene-types and tolerance of electron-rich, readily oxidized functionalities, as well as in their safety and scalability. Herein, we report a method for the difluorination of a number of unactivated alkene-types that is tolerant of electron-rich functionality, giving products that are otherwise unattainable. Key to success is the electrochemical generation of a hypervalent iodine mediator using an “ex-cell” approach, which avoids oxidative substrate decomposition. The more sustainable conditions give good to excellent yields in up to decagram scales.     

Improving efficiency for removal of ammoniacal nitrogen from wastewaters using hydrodynamic cavitation

The present study reports significant improvements in the removal of ammoniacal nitrogen from wastewater which is an important problem for many industries such as dyes and pigment, distilleries and fisheries. Pilot plant studies (capacity, 1 m³/h) on synthetic wastewater using 4-amino phenol as model nitrogen containing organic compound and two real industrial effluents of high ammoniacal nitrogen content were carried out using hydrodynamic cavitation. Two reactor geometries were evaluated for increased efficiency in removal-orifice and vortex diode. Effect of initial concentration (100–500 mg/L), effect of pressure drop (0.5–5 bar) and nature of cavitating device (linear and vortex flow for cavitation) were evaluated along with effect of salt content, effect of hydrogen peroxide addition and aeration. Initial concentration was found to have significant impact on the extent of removal: ~ 5 g/m³ removal for initial concentration of 100 mg/L and up to 12 g/m³ removal at high concentration of 500 mg/L. Interestingly, significant improvement of the order of magnitude (up to 8 times) in removal of ammoniacal nitrogen could be obtained by sparging air or oxygen in hydrodynamic cavitation and a very high removal of above 80% could be achieved. The removal of ammoniacal nitrogen by vortex diode was also found to be effective in the industrial wastewaters and results on two different effluent samples of distillery industry indicated up to 75% removal, though with longer time of treatment compared to that of synthetic wastewater. The developed methodology of hydrodynamic cavitation technology with aeration and vortex diode as a cavitating device was found to be highly effective for improving the efficiency of the conventional cavitation methods and hence can be highly useful in industrial wastewater treatment, specifically for the removal of ammoniacal nitrogen.