Preparation of sphere-shaped nanoscale carbon nitride polymer

The carbon nitride polymer of the previously unknown sphere-shaped structure was prepared both by a template-directed solid-state and solution phase syntheses from cyanuric chloride or fluoride and lithium nitride. The obtained polymer powder was characterized by SEM/EDAX, TEM, XRD, TGA, XPS, (¹³C) MAS NMR, LD/MS, FTIR, UV-visible, and Raman spectroscopy. Modification of the surface area of the template used demonstrated the possibility of producing the carbon nitride spheres with the particle sizes ranging from 20 m to 50 nm. According to TEM data, the spheres are hollow and the material is shown to be essentially amorphous by powder XRD.     

Promoting condensation kinetics of polymeric carbon nitride for enhanced photocatalytic activities

Polymeric carbon nitride(CN)semiconductor by thermal condensation of N-rich precursors has attracted much attention for its capability ranging from photocatalytic and photoelectrochemical energy conversion to biosensing.However,the influence of condensation process on the final structure of CN was rarely studied,making the condensation kinetic far from be fully optimized.Herein,we report the preparation of CN by a simple condensation kinetics modulation using a faster ramping rate during the polymerization process.The modified condensation recipe was even simpler than the conventional one,but led to an improved photocatalytic H2 evolution up to 3 times without any additional chemicals or other complements.Detailed mechanism studies revealed the increase of crystallinity and surface area due to the rapid condensation played the key roles.This work would offer a more facile and effective way to prepare bulk CN for large-scale industrial applications of bulk CN with higher photocatalytic actives for sustainable energy,environmental and biosensing.     

Self-assembling and size-selective synthesis of Ni and NiO nanoparticles embedded in ordered mesoporous carbon and polymer frameworks

We demonstrate the self-assembling and size-selective synthesis of uniform and highly dispersed Ni or NiO nanoparticles with diameters below 12 nm embedded in ordered mesoporous carbon or polymer frameworks. Self-assembly is induced by evaporation of the solvent from a mixture of metal-containing liquid crystalline (LC) mesophases of triblock copolymer and transition metal nitrate hydrate, and the carbon source is low-polymerized phenolic resol. Characterization by XRD, N(2) sorption isotherms, TEM, HRSEM, ICP-AES, TG, and XPS techniques has indicated an ordered 2D hexagonal mesostructure, high surface areas between 524 and 721 m(2) g(-1), uniform pore sizes of about 4.0 nm, large pore volumes ranging from 0.34 to 0.58 cm(3) g(-1), and metal contents ranging from 0.6 to 10.0 wt%. There is a high degree of dispersion, and a small size of nanoparticles throughout the whole framework, without aggregation outside of the pores due to the confinement effect of the mesoporous ordered matrix. The mesoporous solids show excellent adsorption properties for dyes and permit an easy magnetic separation procedure. This method is expected to be applicable to other mesoporous transition metal(oxide)-containing carbon catalysts.     

Efficient strategies for boosting the performance of 2D graphitic carbon nitride nanomaterials during photoreduction of carbon dioxide to energy-rich chemicals

Nowadays, the alarming growing interest in providing a solution to increasing concentration of atmospheric carbon dioxide (CO₂) and the associated pollution has attracted global attention. The consequential effects of CO₂ are detrimental to the environment owing to the continuous depletion of carbon-emitting fossil fuels. Photocatalytic CO₂ reduction (CO₂R) to valuable chemicals and fuels is one the promising alternative option to mitigate the global menace instigated by CO₂ emissions. If the strategies for enhancing the CO₂R are unavailable, inefficient, or inappropriate, then efficiency conversion CO₂ to valuable products can become problematic. In that case, the emission of CO₂ results in synchronizing upsurge in the global-mean air surface temperature on the earth and sea levels from 1980 to 2100. This study presents different strategies for boosting the photocatalytic performance of 2D graphitic carbon nitride (g-C₃N₄) for CO₂R reaction. The first part consists of the fundamental principles of photocatalysis. The second part presents some answers to the question: what governs the mechanism of photocatalytic CO₂R? The existing literature lack comprehensive information about the strategical influence of available reactor designs on the photoactivity of 2D g-C₃N₄ for CO₂ conversion to energy-rich chemicals and ways to improve them as discussed in this study. This was then followed by strategies about the synthetic methods for enhancing photocatalytic CO₂R over 2D g-C₃N₄ materials before the discussion of the strategies for enhancing the CO₂ photoreduction on the 2D g-C₃N₄ nanomaterials. Some groups of g-C₃N₄ nanomaterials for photoreduction of CO₂R were also discussed. Unlike the previous reviews in the field, the present study presents some innovation to bridge the knowledge gaps of the previous reviews and corresponding insight thereof. For future breakthroughs, this study also explains some problems with the interpretation in the field. We also highlight insights into innovation on exclusion and inclusion criteria about the performance metrics and present some queries, concerns, and problems with the previous studies. The concluding part consists of research outlooks, including commonly overlooked challenges and future perspectives for ensuring highly efficient strategies, applications of 2D g-C₃N₄ photocatalysts, and CO₂ conversion to meet industrial scale expectations. The present study hypothesized that considering the current technological age, the experiment should go beyond presenting only illustration and analysis about the band energy, but the detailed explanation/information about the pathways of the various products formed using molecular dynamics system and artificial intelligence aspects should be combined in the future studies.     

Stabilization of octacoordinate carbon center in metal-containing derivatives of orthocarbonic acid

The electronic and spatial structures of alkali metal compounds CO₃M₂, CO₃M₃ ⁺, and CO₄M₄ (M = Li, Na, K) were investigated by the ab initio (MP2(full)/6-311+G**) and density functional (B3LYP/6-311+G**) methods. The calculated energies of formation decrease in the order E ^Li > E ^Na > E ^K for all structural types, being determined by steric and orbital interactions. Stable structures with octacoordinate carbon are formed in the case of CO₄M₄ salts. Dedicated to Academicians A. L. Buchachenko and N. S. Zefirov on the occasions of their 70th birthdays. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1929–1938, September, 2005.     

Ionothermal synthesis of crystalline, condensed, graphitic carbon nitride

Herein we report the synthesis of a crystalline graphitic carbon nitride, or g-C(3)N(4), obtained from the temperature-induced condensation of dicyandiamide (NH(2)C(=NH)NHCN) by using a salt melt of lithium chloride and potassium chloride as the solvent. The proposed crystal structure of this g-C(3)N(4) species is based on sheets of hexagonally arranged s-heptazine (C(6)N(7)) units that are held together by covalent bonds between C and N atoms which are stacked in a graphitic, staggered fashion, as corroborated by powder X-ray diffractometry and high-resolution transmission electron microscopy.     

Chiral metal-containing ionic liquid:Synthesis and applications in the enantioselective cycloaddition of carbon dioxide to epoxides

A series of novel chiral metal-containing ionic liquids(CMILs) consisting of the cation of crown ether-chelated potassium/sodium and the anion of chiral amino acids were designed and synthesized.These new CMILs were used to catalyze the enantioselective cycloaddition of epoxides and carbon dioxide incorporating with the salenCo(OOCCCl3) to generate corresponding chiral cyclic carbonates under mild conditions.These new catalysts can be recycled at least five times without significant loss of activity and ena...     

Cubic and hexagonal mesoporous carbon in the pores of anodic alumina membranes

Cubic and circular hexagonal mesoporous carbon phases in the confined environment of the pores of anodic alumina membranes (AAM) were obtained by organic-organic self-assembly of a preformed oligomeric resol precursor and the triblock copolymer templates Pluronic F127 or P123, respectively. Casting and solvent evaporation were followed by self-assembly and the formation of a condensed wall material by thermopolymerization of the precursor oligomers, thus resulting in mesostructured phenolic resin phases. Subsequent thermal decomposition of the surfactant and carbonization were achieved through thermal treatment at temperatures up to 1000 °C under an inert atmosphere. The resulting hierarchical mesoporous composite materials were characterized by small-angle X-ray scattering and nitrogen-sorption measurements. The structural features were directly imaged in TEM cross-sections of the composite membranes. For both structures, the AAM pores were completely filled and no shrinkage was observed due to strong adhesion of the carbon-wall material to the AAM pore walls. As a consequence, the pore size of the mesophase system stays almost constant even after thermal treatment at 1000 °C.     

Functionalization of mesoporous carbon with superbasic MgO nanoparticles for the efficient synthesis of sulfinamides

Highly basic MgO nanoparticles with different sizes have been successfully immobilized over mesoporous carbon with different pore diameters by a simple wet-impregnation method. The prepared catalysts have been characterized by various sophisticated techniques, such as XRD, nitrogen adsorption, electron energy loss spectroscopy, high-resolution TEM, X-ray photoelectron spectroscopy, and the temperature-programmed desorption of CO(2). XRD results reveal that the mesostructure of the support is retained even after the huge loading of MgO nanoparticles inside the mesochannels of the support. It is also demonstrated that the particle size and dispersion of the MgO nanoparticles on the support can be finely controlled by the simple adjustment of the textural parameters of the supports. Among the support materials studied, mesoporous carbon with the largest pore diameter and large pore volume offered highly crystalline small-size cubic-phase MgO nanoparticles with a high dispersion. The basicity of the MgO-supported mesoporous carbons can also be controlled by simply changing the loading of the MgO and the pore diameter of the support. These materials have been employed as heterogeneous catalysts for the first time in the selective synthesis of sulfinamides. Among the catalysts investigated, the support with the large pore diameter and high loading of MgO showed the highest activity with an excellent yield of sulfinamides. The catalyst also showed much higher activity than the pristine MgO nanoparticles. The effects of the reaction parameters, including the solvents and reaction temperature, and textural parameters of the supports in the activity of the catalyst have also been demonstrated. Most importantly, the catalyst was found to be highly stable, showing excellent activity even after the third cycle of reaction.     

Cleaning of pyrolytic hexagonal boron nitride surfaces

Hexagonal boron nitride (h‐BN) has recently garnered significant interest as a substrate and dielectric for two‐dimensional materials and devices based on graphene or transition metal dichalcogenides such as molybdenum disulfide (MoS₂). As substrate surface impurities and defects can negatively impact the structure and properties of two‐dimensional materials, h‐BN surface preparation and cleaning are a critical consideration. In this regard, we have utilized X‐ray photoelectron spectroscopy to investigate the influence of several ex situ wet chemical and in situ thermal desorption cleaning procedures on pyrolytic h‐BN surfaces. Of the various wet chemistries investigated, a 10 : 1 buffered HF solution was found to produce surfaces with the lowest amount of oxygen and carbon contamination. Ultraviolet/ozone oxidation was found to be the most effective ex situ treatment for reducing carbon contamination. Annealing at 1050 °C in vacuum or 10^?5 Torr NH₃ was found to further reduce oxygen and carbon contamination to the XPS detection limits. Copyright © 2015 John Wiley & Sons, Ltd.     

Polymer‐supported pyridinium catalysts for synthesis of cyclic carbonate by reaction of carbon dioxide and oxirane

Polymer‐supported pyridinium salts, prepared by quaternarization of crosslinked poly(4‐vinylpyridine) with alkyl halides, effectively catalyze the reaction of carbon dioxide (1 atm) and glycidyl phenyl ether (GPE) to afford the corresponding five‐membered cyclic carbonate (4‐phenoxymethyl‐1,3‐dioxolan‐2‐one). Poly(4‐vinylpyridine) quarternarized with alkyl bromides show high catalytic activities, and the reaction of carbon dioxide (1 atm) and GPE at 100 °C affords 4‐phenoxymethyl‐1,3‐dioxolan‐2‐one quantitatively in 6 h. The rate constant in the reaction of GPE and carbon dioxide in N‐methyl pyrrolidinone using poly(4‐vinylpyridine) quarternarized with n‐butyl bromide (k_obs = 102 min^?1) is almost comparable with those for homogeneous catalysts with good activities (e.g., LiI), and the rate of the reaction obeys the first‐order kinetics. A used catalyst may be recovered by centrifugation, and the recycled catalyst also promotes the reaction of GPE and carbon dioxide. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5673–5678, 2007     

Lignin bio-oil-based electrospun nanofibers with high substitution ratio property for potential carbon nanofibers applications

We reported a new approach for development of lignin bio-oil-based electrospun nanofibers (LENFs) that had high substitution ratio (up to 80 wt%) and good morphology. This approach was particularly unique and translatable as it used small molecule lignin bio-oil with high reactivity and low heterogeneity obtained via lignin depolymerization reaction to produce well-oriented LENFs. Firstly, effects of various blends solutions ratios and electrospinning parameters on the characteristics of the obtained LENFs were analyzed. The results showed that the optimal parameters that resulted in the best electrospun nanofibers were as follows: blend solution ratio, the 20 wt% blend solution containing 80 wt% straw lignin bio-oil (SLB) and 20 wt% polyacrylonitrile (PAN), flow rate, 1 mL/h, voltage, 20 kV, rotational speed, 500 r/min and the distance between needle and collection screen, 20 cm. Secondly, used the best LENFs, we also applied to prepare lignin bio-oil-based carbon nanofibers (LCNFs) and estimated its properties by scanning electron microscope (SEM), X-ray diffraction (XRD) patterns, Raman spectroscopy and tension testing. Our results demonstrated that compared with pure PAN carbon nanofibers (PCNFs), the as-prepared LCNFs had similar smooth surfaces, similar crystallinity and similar mechanical properties. This work can promote the utilization of lignin depolymerization main-products to produce lignin-based materials, while also help to reduce use of high-cost PAN.     

Energetic stability of boron nitride nanostructures doped with one carbon atom

We have investigated, using first‐principles calculations, the role of a substitutional carbon atom on the geometric stability of boron nitride monolayers, nanotubes, and nanocones. It is shown that the formation of energy depends on the number of atoms for the monolayers and on the diameter for the tubes. It is also found, for the carbon‐doped boron nitride nanotubes, that the value for the strain energy approaches the one obtained for nondoped tubes with increasing diameter. For the structural stability, we have verified that the doping, which introduces an excess of nitrogen or boron, makes each structure more favorable in its reverse atmosphere, i.e., excess of nitrogen is more stable in a boron‐rich growth environment, whereas excess of boron is preferred in a nitrogen‐rich condition. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

简便方法合成含铁石墨相氮化碳材料及其催化苯直接羟基化制苯酚（英文）

苯酚是一种重要的基本有机化工原料.全球近90%的苯酚都是经"三步异丙苯法"工艺合成而得,但是该工艺存在单程苯酚收率低(5%)、酸污染严重等不足.同时由于联产丙酮,苯酚的产量也受丙酮市场所制约.由苯经氧化或羟基化一步法合成苯酚是催化化学领域中一项极具挑战的课题.由于苯分子较难活化,而苯酚易于深度氧化,因此研发和设计具有高活性和高选择性的催化剂是该课题的研究核心.因具有诸多特殊的理化性质,石墨相氮化碳(g-C_3N_4)作为一种新型碳质材料近年来在光催化、热催化、燃料电池和气体吸附等领域展示出广阔的应用前景.g-C_3N_4的类石墨层基本单元为大π共轭的三均三嗪环,对苯分子具有良好的吸附和活化能力.目前,g-C_3N_4(尤其是具有高比表面的介孔材料)在苯Friedel-Crafts烷基化和酰基化反应、苯的CO2氧化等反应中均显示了良好的催化活性.尽管如此,由于缺乏合适的氧化活性中心,纯的g-C_3N_4对苯直接羟基化几乎无催化活性.本课题组曾将乙酰丙酮氧钒和氧化钒负载至介孔g-C_3N_4,发现该类催化剂在H2O2参与的苯直接羟基化反应中,苯转化率高达18%,而苯酚选择性大于95%.然而,此类介孔g-C_3N_4均采用硬模板法合成,制备周期长且需要HF溶液蚀刻氧化硅模板.另外,钒基组分在介孔g-C_3N_4表面也存在着部分溶脱现象.本文以FeCl_3和二氰二胺为前驱体,通过一步热解法直接合成了含铁的g-C_3N_4材料(Fe-g-C_3N_4).采用N2吸附-脱附、XRD、TG、FT-IR、UV-vis、XPS光谱和TEM对材料的理化性质进行表征.结果显示,Fe的原位引入能显著提高g-C_3N_4的比表面积和孔体积,且使其依然保持石墨相结构.同时,富N的g-C_3N_4材料能有效地锚定Fe离子,使其均匀地分散在载体表面.作为多相催化剂,Fe-g-C_3N_4在H_2O_2环境下对苯羟基化合成苯酚的反应表现出较高的催化活性.当反应温度为60°C,其苯酚收率最高可达17.5%,且回收使用多次催化剂活性表现稳定.与之前报道的含铁和负载氧化钒或乙酰丙酮氧钒的g-C_3N_4催化剂材料相比,Fe-g-C_3N_4催化剂制备工艺更加简便.     

Synthesis of Two‐dimensional Microporous Carbonaceous Polymer Nanosheets and Their Application as High‐performance CO2 Capture Sorbent

The synthesis of two‐dimensional (2D) polymer nanosheets with a well‐defined microporous structure remains challenging in materials science. Here, a new kind of 2D microporous carbonaceous polymer nanosheets was synthesized through polymerization of a very low concentration of 1,4‐dicyanobenzene in molten zinc chloride at 400–500 °C. This type of nanosheets has a thickness in the range of 3–20 nm, well‐defined microporosity, a high surface area (～537 m² g^?1), and a large micropore volume (～0.45 cm³ g^?1). The microporous carbonaceous polymer nanosheets exhibit superior CO₂ sorption capability (8.14 wt % at 298 K and 1 bar) and a relatively high CO₂ selectivity toward N₂ (25.6). Starting from different aromatic nitrile monomers, a variety of 2D carbonaceous polymer nanosheets can be obtained showing a certain universality of the ionothermal method reported herein.     

One‐shot synthesis of high molar mass polyurethane in supercritical carbon dioxide

Well‐defined polyurethane–polydimethylsiloxane particles of tunable diameter in the range of 0.5–20 μm were synthesized in “one‐shot” by step‐growth polymerization using supercritical carbon dioxide (scCO₂) as a dispersant medium. Polymerizations were carried out at 60 °C and above 25 MPa, after the solubility of each reactant in scCO₂ has been determined in its typical reaction concentration. The synthesis of such copolymers was achieved by polyaddition between short aliphatic diols, that is, ethylene glycol, 1,4‐butanediol (BD) or polyethylene oxide (M_n = 200 g mol^?1), and tolylene‐1,4‐di‐isocyanate (TDI) in the presence of mono or di‐isocyanate‐terminated polydimethylsiloxane (PDMS) as reactive stabilizers and dibutyltin dilaurate as a catalyst. The nature of the diol used as well as the functionality of the reactive stabilizer incorporated was found to have a dramatic effect on the molar mass and the morphology of the resulting product. Thus, copolymers obtained from the polyaddition of BD and TDI in the presence of di‐isocyanate‐terminated PDMS exhibit molar mass up to 90,000 g mol^?1. Thermal behaviors of copolymers were also examined by differential scanning calorimetry. All samples exhibited only one glass transition temperature (T_g) and were found to be totally amorphous. A logical decrease of the T_g was observed as the length of the diol incorporated increased, that is, as the density of urethane linkages within the polymer decreased. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5649–5661, 2007     

Spontaneous coating of carbon nanotubes with an ultrathin polypyrrole layer

A novel protocol for precisely coating individual multiwall carbon nanotubes (MWCNTs) with an ultrathin layer of polypyrrole was developed. The nanocoated MWCNTs were successfully prepared by in situ chemical deposition of polypyrrole in an aqueous suspension of MWCNTs. The coating layer was very uniform and the thickness of the layer was determined by controlling the monomer concentration used, which gave nanometer precision. The products were characterized by transmission electron microscopy, scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, electron energy loss spectroscopy, and conductivity and current-voltage measurements. The ultrathin polypyrrole layer could electrically insulate individual MWCNTs.