天津大学吴洪教授、姜忠义教授在超薄纳滤膜上取得新进展

<正>天津大学吴洪教授、姜忠义教授团队采用共价有机框架介导界面聚合的策略,利用二维固有孔材料在基底上首先构筑高孔隙率超亲水层,再进行界面聚合,成功制备出超薄聚酰胺纳滤膜。合成了具有高比表面积且富含亲水基团(胺基、酮基)的TpPa-1型共价有机框架纳米片(CONs)作为构筑单元,在基底上组装一层CONs复合基膜。在界面聚合过程中,CLS层可高效储存胺单体,并优化单体分布与扩散,与TMC     

sp2碳共价有机框架可见光催化水分子氧化

为开发出具有强π-π共轭效应、优异可见光转化性能及高光催化析氧反应（OER）活性的共价有机框架（COFs）材料， 以具有较大共轭结构的N,N’-对乙腈苯-3,4,9,10-萘二酰亚胺和1,3,5-三(对甲酰基苯基)苯为单体，通过溶剂热方法合成了sp2碳连接构筑的六方孔状的NP-COF，并通过结构、形貌、光电性能表征表明了NP-COF是一种吸光性能良好、具有一定的载流子产生和迁移能力优势的半导体型催化剂，能够在可见光诱导下高效地催化水分子氧化反应的进行，在7.4 mg Co(NO3)2?6H2O作为助催化剂的条件下平均产氧速率达344 μmol/(g·h)。     

共价有机框架材料吸附去除重金属离子研究进展

共价有机框架（covalent organic framework,COF）材料是近些年来非常有研究热度的多孔材料。由于其具有孔隙率高、比表面积大、功能及结构可调、丰富的活性吸附位点等优点,被广泛应用于气体储存、催化、光电传导和吸附等方面。从共价有机框架材料的合成策略、结构特性及物理化学性质出发,综述了共价有机框架材料作为新型吸附剂对水体中重金属离子吸附去除的应用,阐述了共价有机框架材料在吸附重金属离子方面的吸附条件、吸附性能、吸附效果以及吸附机理。对共价有机框架材料的应用现状进行了论述,最后,展望了共价有机框架材料的未来发展方向。     

共价有机框架(COFs)材料最新应用研究进展

共价有机框架材料是一类由共价键构筑,具有周期性结构和结晶性的有机多孔聚合物。由于共价有机框架材料由轻质子元素链接,密度比较小,热稳定性比较高,而且因为其多孔性,在气体吸附、能量存储、非均相催化等领域得到了广泛应用。本文综述了近年来COFs材料在环境污染物治理领域的最新研究进展。     

中科院大连化物所制备出高性能超薄二氧化碳分离膜

正在碳达峰碳中和的国家战略目标背景下,发展低能耗、环境友好的CO_2选择性分离膜具有重要意义和实际应用价值。高性能二维分离膜是该研究领域前沿性研究议题。中国科学院大连化学物理研究所无机膜与催化新材料研究组(504组)杨维慎研究员、彭媛副研究员团队在纯相共价有机框架气体分离膜研究方面取得新进展,以共价有机框架纳米片为膜构筑基元,诱发错排缩孔效应,成功实现了二氧化碳的高效分离。     

基于Aldol缩合反应的碳碳双键共价有机框架材料的设计合成

具有C₃对称性的三甲基三嗪（TMT）分别与2,4,6-三(4-醛基苯基)-1,3,5-三嗪（TFPT）、均三苯甲醛（TFB）和四氟对苯二甲醛（TFBA）在酸或者碱催化条件下发生Aldol缩合反应,成功构建出3种新型的碳碳双键桥联的共价有机框架材料（TMT-TFPT-COF、TMT-TFB-COF、TMT-TFBA-COF）。本研究通过Material Studio、ZEO⁺⁺等软件对材料进行结构的精确解析,并结合粉末X射线衍射（PXRD）、傅里叶红外光谱（FTIR）等表征手段确定了材料的结构、连接方式及其荧光特性。结果表明,这3种较高结晶度的新型共价有机框架材料均为二维层层堆积结构,其中碱催化条件下合成的TMT-TFPT-COF、TMT-TFB-COF材料呈现出良好的荧光性质,此类荧光COFs材料在光催化、化学传感器等方面具有很好的应用潜力。     

共价有机框架材料的制备及对染料吸附性能的研究

利用溶剂热法合成了一种二维的共价有机框架（DMTP-TAPB COF）材料。通过X射线衍射仪（XRD）、扫描电子显微镜（SEM）和热重分析仪（TGA）对合成材料的结构、形貌和性能进行了详细的研究。然后研究了制备的共价有机框架材料对于靛蓝胭脂红染料（IC）的吸附能力，考察了不同吸附时间、不同p H和不同靛蓝胭脂红的初始浓度对吸附性能的影响。实验结果表明，制备的二维共价有机框架材料具有良好的结晶度和均匀的形貌。同时，DMTP-TAPB COF对靛蓝胭脂红具有较高的吸附能力（330.5 mg/g）和移除效率（84.5%），吸附过程符合准二级动力学方程和Langmuir吸附模型。该研究表明共价有机框架材料作为污染物的吸附剂具有广阔的应用前景。     

碳纳米环：生长机理、可控合成、性质和应用

碳材料是一类神奇的材料,碳原子可以通过sp、sp2或sp3杂化构筑不同微观结构的碳材料。目前,已经发现的碳的同素异形体有石墨、金刚石、富勒烯、碳纳米管、碳纳米环、石墨烯和石墨炔。富勒烯和石墨烯因性质独特、应用前景广阔,其发现者分别获得1996年和2010年诺贝尔奖。碳纳米环具有独特的环状结构、优异的机械强度及特殊的物理化学性能,也引起广泛关注。研究者从早期对碳纳米环进行理论计算、预测其性质,到现在已能够通过化学气相沉积、激光辐射、超声诱导自组装等方法制备不同尺寸的碳纳米环,并对其性质和应用进行探索。总结了近30年来有关碳纳米环的生长机理、可控合成、性质和应用等方面的研究进展,对其规模化合成与应用提出了建议与展望。     

二维共价有机框架膜的构筑及其气体分离研究进展

二维共价有机框架材料由于具有层状堆积结构,构筑单元丰富、孔道规整且精确可调、易于修饰功能基团,具有良好的化学、机械和热稳定性能,相较于其它晶体材料,二维共价有机框架在制备气体分离膜时的成膜性更好,有望制备成超薄膜。本文从二维共价有机框架膜的制备、性能改善及气体分离应用研究三个方面进行综述,并对其研究前景进行展望。     

微流控制备金属/共价有机框架功能材料研究进展

近年来,金属有机框架(MOFs)和共价有机框架(COFs)等多孔材料因其结构单元的多样性和可设计性,不仅可以构筑具有多样化拓扑类型和化学物理性质的骨架结构,还可以精准调节结构中孔道的形状、大小和孔径分布,在气体吸附与分离、催化和化学传感等方面展现出广泛的应用价值。然而传统间歇式合成方法中相际间缓慢的微观传递过程,不利于材料的连续均一制备。近年来,微流控技术连续操作、精准可控、传递效率高和高度可重复性等特点在纳米材料制备领域体现了独有的优势。本文综述了近年来利用微流控技术制备MOF和COF材料的研究成果,重点介绍微流控强化合成过程,实现快速制备MOF和COF功能材料,以及通过微流体精准调控多孔材料微结构的研究工作。     

可见光催化构建碳氮键的研究进展

可见光是一种清洁的可再生能源,利用可见光代替传统的热能进行化学转化具有绿色、高效的优点.碳氮键是广泛存在于多种生物活性分子和药物分子中的重要化学键,光催化构筑碳氮键在有机和药物化学领域中具有重要研究意义.近年来光催化形成碳氮键研究得到了快速发展,许多新颖的合成方法不断涌现.综述了可见光催化构建C(sp2)—N键和C(s...     

Evaluation of diamond films by nuclear magnetic resonance and Raman spectroscopy

The quality of chemically vapor deposited diamond films was assessed in terms of sp²/sp³ content as determined by solid-state nuclear magnetic resonance (NMR) and Raman spectroscopy. While the results of the two techniques are in qualitative agreement, only the NMR spectra yield quantitative values for the sp²/sp³ ratio. Only sp³ carbon was observed in the NMR spectra of very high quality hot-filament, microwave plasma, and d.c. arc-jet chemically vapor deposited films. As expected, Raman spectroscopy is extremely sensitive to sp² bonded carbon, identifying small amounts below the detection limit of the NMR spectrometer. Comparison of the two techniques, however, indicates that Raman spectroscopy may be so sensitive to sp² bonded carbon that sp³ bonded carbon in films containing as much as 90% sp³ bonded material may remain undetected. NMR linewidths indicate that the sp³ carbon in such material shows more disorder than that found in high-quality polycrystalline films.     

Influence of nitrogen ion energy on the Raman spectroscopy of carbon nitride films

Carbon nitride films were deposited by filtered cathode vacuum arc combined with radio frequency nitrogen ion beam source. Both visible Raman spectroscopy and UV Raman spectroscopy are used to study the bonding type and the change of bonding structure in carbon nitride films with nitrogen ion energy. Both C–N bonds and CN bonds can be directly observed from the deconvolution results of visible and UV Raman spectra for carbon nitride films. Visible Raman spectroscopy is more sensitive to the disorder and clustering of sp² carbon. The UV (244 nm) Raman spectra clearly reveal the presence of the sp³ C atoms in carbon nitride films. Nitrogen ion energy is an important factor that affects the structure of carbon nitride films. At low nitrogen ion energy (below 400 eV), the increase of nitrogen ion energy leads to the drastic increase of sp²/sp³ ratio, sp² cluster size and C---N bonds fraction. At higher nitrogen ion energy, increase leads to the slight increase of CN bonds fraction and sp² cluster size, slight decrease of C---N bonds fraction and sp²/sp³ ratio.     

Characterization of d.c.jet CVD diamond films on molybdenum

Diamond films grown using a thermal plasma technique are characterized using a variety of techniques. The relationships between the chemistry, morphology, and mechanical properties are explored using microscopy, Raman spectroscopy, Auger electron spectroscopy, and X-ray photoelectron spectroscopy. The characteristics of films grown using two different nucleation enhancement techniques are shown. Films grown using high methane concentrations at the beginning of growth produce large grained columnar films, whereas films grown on substrates which have been treated with a diamond polishing step show nanocrystalline structures. Variations in sp³ and sp² bonding and peak shifts are tracked through the thickness of the film, corresponding to variations in the methane concentration during growth. Stresses are measured using peak shifts and beam bending techniques. Adhesion is tested using indentations, and is shown to increase both as growth temperatures and surface roughness increase.     

Synthesis of nanocrystalline nitrogen-rich carbon nitride powders at high pressure

Nitrogen-rich carbon nitride powders with composition close to C₄N_2.8–3.3 were synthesized by using a chemical reaction between sodium azide and hexachlorobenzene under high pressure (7.7 GPa) and a temperature of 500 °C for 30 min. The final black powders were relatively hard materials with high resistance to hot acids and common organic solvents. Analytical electron microscopy and X-ray diffraction studies showed that the powders are predominantly amorphous, containing nanometer-sized crystallites. Carbon and nitrogen K-edge structures obtained by electron energy-loss spectroscopy suggest the existence of chemical bonding between C and N, and that the amorphous carbon nitride matrix is primarily sp²-bonded. Raman and infrared features of the carbon nitride powders closely resemble those in carbon and diamond-like films and also characterize the powders as strongly disordered, sp²-bonded carbon nitride exhibiting graphite-like microdomains with dimensions of approximately 1 nm.     

Deposition of carbon nitride films by filtered cathodic vacuum arc combined with radio frequency ion beam source

Atomically smooth carbon nitride films were deposited by an off-plane double bend filtered cathodic vacuum arc (FCVA) technique. A radio frequency nitrogen ion source was used to supply active nitrogen species during the deposition of carbon nitride films. The films were characterized by atomic force microscopy (AFM), XPS and Raman spectroscopy. The internal stress was measured by the substrate bending method. The influence of nitrogen ion energy (0–1000 eV) on the composition, structure and properties of the carbon nitride films was studied. The nitrogen ion source greatly improves the incorporation of nitrogen in the films. The ratio of N/C atoms in the films increases to 0.40 with an increase in the ion beam energy to 100 eV. Further increase in the ion beam energy leads to a slight decrease in the N/C ratio. XPS results show that nitrogen atoms in the films are chemically bonded to carbon atoms as C---N, C=N, and CN bonds, but most of nitrogen atoms are bonded to sp² carbon. The increase in nitrogen ion energy leads to a decrease in the content of nitrogen atoms bonded to sp² carbon, and an increase in the content of nitrogen atoms bonded to sp³ and sp¹ carbon. Raman spectra indicate an increase in the sp² carbon phase in carbon nitride films with an increase in nitrogen ion energy. The increase in sp² carbon fraction is attributed to the decrease in internal stress with increasing nitrogen ion energy.     

碳纳米环：生长机理、可控合成、性质和应用

碳材料是一类神奇的材料,碳原子可以通过sp、sp²或sp³杂化构筑不同微观结构的碳材料。目前,已经发现的碳的同素异形体有石墨、金刚石、富勒烯、碳纳米管、碳纳米环、石墨烯和石墨炔。富勒烯和石墨烯因性质独特、应用前景广阔,其发现者分别获得1996年和2010年诺贝尔奖。碳纳米环具有独特的环状结构、优异的机械强度及特殊的物理化学性能,也引起广泛关注。研究者从早期对碳纳米环进行理论计算、预测其性质,到现在已能够通过化学气相沉积、激光辐射、超声诱导自组装等方法制备不同尺寸的碳纳米环,并对其性质和应用进行探索。总结了近30年来有关碳纳米环的生长机理、可控合成、性质和应用等方面的研究进展,对其规模化合成与应用提出了建议与展望。     

Structural features of diamond layers photo-emitting at sub-band gap energies

The photoemission behaviour of a series of diamond-based polycrystalline films irradiated by the second (2.3 eV), third (3.5 eV) and fourth (4.7 eV) harmonics produced by a Q-switched-mode-locked Nd: Yag laser has been investigated and related to the structural and compositional characteristics of the layers. The materials were polycrystalline undoped diamond films as well as Nd- and N-containing diamond films grown by CVD techniques, diamond-like and amorphous carbon layers. The morphological and structural characteristics of the films were investigated by electron microscopy, Raman spectroscopy and electron diffraction. The analysis of the photoemission curves does not evidence any improvement of the emission efficiency in the case of Nd-containing films nor for the diamond films grown in the presence of N_2. The results evidence conversely a strong correlation between the characteristics of the photoemission process at sub-band gap energies and the presence of amorphous sp²-C patches located at the diamond film surfaces. The photoemitting properties of our samples are discussed and rationalized by considering charge emission occurring at the sp²-diamond-vacuum border and the emission process governed by the ratio of amorphous sp²-C to crystalline sp³-C. The rather high values of quantum efficiency measured in the course of the present research at 3.5 and 4.7 eV suggest that a proper distribution of amorphous carbon onto a good quality diamond surface is the key factor for the preparation of efficient and stable photocathode materials.     

Large-scale simulations of CO2 diffusion in metal-organic frameworks with open Cu sites

Understanding CO₂ diffusion behavior in functional nanoporous materials is beneficial for improving the CO₂ adsorption, separation, and conversion performances. However, it is a great challenge for studying the diffusion process in experiments. Herein, CO₂ diffusion in 962 metal-organic frameworks (MOFs) with open Cu sites was systematically investigated by theoretical methods in the combination of molecular dynamic simulations and density functional theory (DFT) calculations. A specific force field was derived from DFT-D2 method combined with Grimme's dispersion-corrected (D2) density functional to well describe the interaction energies between Cu and CO₂. It is observed that the suitable topology is conductive to CO₂ diffusion, and 2D-MOFs are more flexible in tuning and balancing the CO₂ adsorption and diffusion behaviors than 3D-MOFs. In addition, analysis of diffusive trajectories and the residence times on different positions indicate that CO₂ diffusion is mainly along with the frameworks in these MOFs, jumping from one strong adsorption site to another. It is also influenced by the electrostatic interaction of the frameworks. Therefore, the obtained information may provide useful guidance for the rational design and synthesis of MOFs with enhanced CO₂ diffusion performance for specific applications.     

Characterization of diamond-like carbon films before and after heavy energetic ion implantations

Hydrogenated diamond-like carbon films were implanted by 110 keV Fe⁺ at doses ranging from 1 × 10¹³ to 5 × 10¹⁶ ions cm⁻². The film resistivities and the infra-red transmittances of the specimens were determined as functions of the implanted doses. Raman spectra and the infra-red transmittances of the film layers were used to characterize the structural changes of the implanted films. It was found that, when the implantation dose was higher than about 5 × 10¹⁴ or 1 × 10¹⁵ ions cm⁻², the film resistivity and the total infra-red transmittance of the specimens decreased significantly. However, when the dose was smaller than this value, the resistivity decreased firstly and then increased with dose and the measured values were higher than those of corresponding as-grown ones. The infra-red transmittance of the specimens was also improved to some extent under the lower dose range. By using structural characterization results, especially the infra-red transmittances of the film layers, we conclude that the electrical and optical property changes at doses higher than about 5 × 10¹⁴ or 1 × 10¹⁵ ions cm⁻² were due to the following changes, i.e., the decrease in the population of both sp² C-H and sp³ C-H bonds (compared with that of sp³ C-H bonds, the decrease in speed of sp² C-H bonds is smaller), the decrease of bond-angle disorder and the increased population of sp² C-C bonds. However, at doses between 1 × 10¹⁴ and 5 × 10¹⁴ or 1 × 10¹⁵ ions cm⁻², the implantation induced increase of C-H bonds was responsible for the observed property changes. Compared with the previous reports, the novelty of the present work is: the IR transmittance curves of the single film layers give us direct evidence for the changes of different C-H bonds with increasing ion dose and thus proved the transformation mechanism proposed previously.