Mesoporous Porphyrin-Silica Nanocomposite as Solid Acid Catalyst for High Yield Synthesis of HMF in Water

Solid acid catalysts occupy a special class in heterogeneous catalysis for their efficiency in eco-friendly conversion of biomass into demanding chemicals. We synthesized porphyrin containing porous organic polymers (PorPOPs) using colloidal silica as a support. Post-modification with chlorosulfonic acid enabled sulfonic acid functionalization, and the resulting material (PorPOPS) showed excellent activity and durability for the conversion of fructose to 5-hydroxymethyl furfural (HMF) in green solvent water. PorPOPS composite was characterized by N₂ sorption, FTIR, TGA, CHNS, FESEM, TEM and XPS techniques, justifying the successful synthesis of organic networks and the grafting of sulfonic acid sites (5 wt%). Furthermore, a high surface area (260 m²/g) and the presence of distinct mesopores of ~15 nm were distinctly different from the porphyrin containing sulfonated porous organic polymer (FePOP-1S). Surprisingly the hybrid PorPOPS showed an excellent yield of HMF (85%) and high selectivity (>90%) in water as compared to microporous pristine-FePOP-1S (yield of HMF = 35%). This research demonstrates the requirement of organic modification on silica surfaces to tailor the activity and selectivity of the catalysts. We foresee that this research may inspire further applications of biomass conversion in water in future environmental research.     

Recent development of pillar[n]arene-based amphiphiles

Pillar[n]arene-based amphiphiles,mainly including amphiphilic pillar[n]arenes and supra-amphiphilic pillar[n]arenes,have obtained considerable interests in recent years due to their fascinating chemical structures,various self-assembly behaviors,and widely applications.Thanks to the pillar-like frameworks and the rich host-guest recognitions of the cavities,these amphiphiles can be easily controlled to form dimensional and morphologic assemblies for multiple applications.Compared with traditional linear covalent amphiphiles,the introduction of host-guest recognitions facilitated the preparation and controllability of these supramolecular amphiphilic systems.Moreover,the host-guest recognitions endow the assemblies from pillar[n]arene-based amphiphiles with stimuli-responsive functions.In this mini-review,we summarized the chemical structures,self-assembly features,and the applications of pillar[n]arene-based amphiphiles.However,several research topics of pillar[n]arenebased amphiphiles can be further developed in the future,such as larger cavity amphiphilic pillar[n]arenes,co-assembly with 2 D materials and utilization of the host-guest interactions.     

Laser-assisted synthesis of cobalt@N-doped carbon nanotubes decorated channels and pillars of wafer-sized silicon as highly efficient three-dimensional solar evaporator

The Co@NCNTs/Si pillars with channels is assemble to a suitable pure water gathering device, which is applied in seawater desalination and sewage purification to produce pure water by utilizing solar energy. High-efficiency utilization of solar energy to generate water vapor is popular, recyclable, and environmentally friendly for seawater desalination and sewage purification, helping to alleviate the global water shortage crisis. Here, we report an efficient and simple method to prepare a three-dimensional (3D) evaporator for steam generation by harnessing the power of the sun. This evaporation is composed of one-dimensional (1D) cobalt embedded and nitrogen doped carbon nanotubes (Co@NCNTs) and 3D silicon pillars array structure (Si pillars). The Co@NCNTs/Si pillars shows a wide light absorption range provided by carbon nanotubes and a long light absorption path because of the silicon pillars. The surface temperature of the sample rises rapidly in 1.5 min and exceed 80 °C under solar illumination of one sun. The water evaporation can be high as 1.21 kg m⁻² h⁻¹ under one sun irradiation (1 kW/m²) with the energy efficiency up to 82.4%. This scalable Co@NCNTs/Si pillars can prepare pure water from seawater and sewage, where the removal rate of ions in seawater and pollutants in sewage is similar to 100%. Based on our research, this multistage three-dimensional structure is a simple and efficient novel photothermal material for extensive seawater desalination and sewage purification.     

NDI-induced Topological Conversion of Human Telomeric G-Quadruplexes from Hybrid-2 to Parallel Form

G-Quadruplexes(GQs), which are formed by G-rich DNA sequences in human telomeres, have become an attractive target for cancer treatment. The ligands to stabilize the conformation of human telomeric GQs in vivo are particularly important for structure-based ligand design and drug development targeting the noncanonical DNA structure. Here we report the conformational conversion of Tel26 induced by a naphthalene diimide(NDI) ligand in K⁺ buffer, even at cellular physiological temperature(37℃) and under mimetic cellular crowding conditions created by Ficoll 70. We provide an insight into the dynamic conversion from initial hybrid-2 GQ topology to final parallel GQ topology. These results are helpful for the design of ligands with GQ conformation regulation.     

Improvement in energy conversion of electrostrictive composite materials by new approach via piezoelectric effect: Modeling and experiments

This study proposes a new model that couples the piezoelectric and electrostrictive behavior to minimize the polarization power of composite polymer. The development of this model is capable to predict the energy harvesting abilities of an electrostrictive composite. To improve the dielectric permittivity of electrostrictive polymer, the particles of PZT have been incorporated in order to increase the conversion efficiency of the composite. Dielectric characterization tests showed an increase in dielectric permittivity by a factor of 4.5 compared to pure polymer. Experimental measurements of harvested power validate the analytical model and demonstrate a good correlation between the two data. An equivalent of an electrical scheme has been developed, which allows modeling the two behaviors. The harvested power density under low frequency at 2% of strain can reach 0.30 μW/cm³ for 33% of PZT without the polarization field, including the conversion efficiency becomes higher. The energy harvester property of this material composite has excellent potential for several self‐powered applications such as wireless sensor networks and the internet of things.     

直接合成Beta沸石封装Pt纳米粒子用于5-羟甲基糠醛合成2,5-呋喃二甲酸

生物质是唯一的碳基可再生资源,具有种类丰富、廉价易得、来源广泛等特点,将生物质资源转化为高附加值化学品对于可持续生产,缓解全球性能源和环境危机具有重要意义.5-羟甲基糠醛(HMF)是广泛研究的生物质平台分子,可以转化为多种高附加值化学品,其中氧化产物2,5-呋喃二甲酸(FDCA)有望作为对苯二甲酸的潜在替代物生产聚酯,因而备受关注.然而如何设计合成高性能的多相催化剂一直是个挑战.以氧气为氧化剂,负载型贵金属纳米粒子作为多相催化剂是目前广为研究的体系,但是面临贵金属利用率低,稳定性不佳等不足.将贵金属纳米粒子封装于沸石骨架,不仅能通过沸石孔壁的物理隔离效应增加纳米粒子的稳定性,同时基于沸石孔道对于底物、中间生成物、产物等特有的传质限域效应,可能会进一步提高活性和选择性.由于沸石晶体一般在碱性水热条件下晶化得到,易导致贵金属物种的快速沉积而难以获得高分散贵金属纳米粒子的沸石催化剂.因此这类催化剂的直接水热合成以及在生物质平台分子转化中的应用至今少有报道.本文设计合成了一种封装铂(Pt)纳米粒子的Beta沸石(Pt@Beta),应用于催化HMF合成FDCA的反应,以常压氧气为氧源,水作为溶剂,获得了高活性和稳定性以及极高的Pt原子利用率.我们采用一种不同以往的酸水解路径合成Pt@Beta沸石.首先将Pt前驱体、硅源(正硅酸四乙酯)和有机配体(3-巯丙基甲氧基硅氧烷)在弱酸性条件下水解缩合,增强了硅物种与Pt物种的相互作用,有效避免了贵金属氢氧化物的形成,这种特殊的预水解缩合环节有效促进了后续碱性环境水热合成中的Pt物种进入沸石晶内的过程,最终形成较为稳定和均匀分散的Pt纳米粒子.系统考察了配体种类、配体用量、配体加料顺序等合成条件对于催化剂制备的影响规律,获得了高分散Pt纳米粒子的适宜合成条件,结果表明,在酸水解过程中加入适量的有机配体,对于最终催化剂中Pt的高度分散至关重要.将不同Pt含量的Pt@Beta和后负载方法制备的Pt/Beta进行细致对比,XPS和TEM表征结果发现,只有直接水热合成法能够将Pt较好地封装在沸石晶体内.封装较低含量Pt的样品(0.2%Pt@Beta)在HMF氧化制FDCA反应中表现出高的收率和良好的复用稳定性.为探究其高活性缘由,测试了不同催化剂对底物、中间体以及产物的吸附性能,结果表明,0.2%Pt@Beta对于中间体2-甲酰呋喃甲酸(FFCA)吸附能力较强,能有效加速FFCA到FDCA这一决速步的反应,从而促进了FDCA的生成.此外,0.2%Pt@Beta中贵金属物种位于沸石晶内,得益于沸石刚性无机骨架的稳定化作用,该催化剂能有效阻止Pt纳米粒子在苛刻条件下的聚集,避免液固相反应体系中的溶脱流失,从而表现出优良的催化复用稳定性.     

Study of the Lithium Storage Mechanism of N-Doped Carbon-Modified Cu2S Electrodes for Lithium-Ion Batteries

Owing to their high specific capacity and abundant reserve, Cu_xS compounds are promising electrode materials for lithium-ion batteries (LIBs). Carbon compositing could stabilize the Cu_xS structure and repress capacity fading during the electrochemical cycling, but the corresponding Li⁺ storage mechanism and stabilization effect should be further clarified. In this study, nanoscale Cu₂S was synthesized by CuS co-precipitation and thermal reduction with polyelectrolytes. High-temperature synchrotron radiation diffraction was used to monitor the thermal reduction process. During the first cycle, the conversion mechanism upon lithium storage in the Cu₂S/carbon was elucidated by operando synchrotron radiation diffraction and in situ X-ray absorption spectroscopy. The N-doped carbon-composited Cu₂S (Cu₂S/C) exhibits an initial discharge capacity of 425 mAh g⁻¹ at 0.1 A g⁻¹, with a higher, long-term capacity of 523 mAh g⁻¹ at 0.1 A g⁻¹ after 200 cycles; in contrast, the bare CuS electrode exhibits 123 mAh g⁻¹ after 200 cycles. Multiple-scan cyclic voltammetry proves that extra Li⁺ storage can mainly be ascribed to the contribution of the capacitive storage.     

在碳纤维布上原位生长NiCo层状双氢氧化物纳米片用于高性能非对称超级电容器

通过恒电压电沉积法在不同的碳纤维基体上原位制备NiCo层状双金属氢氧化物(NiCo-LDH)复合材料(NiCo-LDH/碳纤维布),该方法无需粘合剂,可以有效避免由于粘合剂的加入引起的导电性降低。在NiCo-LDH的层状晶体结构中,正电荷的主体层和层间电荷补偿阴离子可以促进电极材料之间的离子扩散,从而可高效利用活性位点。得益于NiCo-LDH折叠层状结构的特点,NiCo-LDH/碳纤维布具有出色的比电容(1 A·g^-1时1387.5 F·g^-1)。此外,以NiCo-LDH/碳纤维布作为正极,涂覆在泡沫镍表面的还原氧化石墨烯(rGO/NF)作为负极,组装而成的非对称超级电容器(ASC)具有极好的电化学性能。ASC在1 A·g^-1时能量密度为26.6 Wh·kg^-1,功率密度为850.4 W·kg^-1,在最大功率密度为8500.3 W·kg^-1时能量密度仍保持有14.9 Wh·kg^-1。     

介孔碳-碳纳米管-硫化铜复合材料对电极的制备及其在量子点敏化太阳能电池中的应用

首先研究了介孔碳(MC)、碳纳米管(CNT)和不同MC/CNT质量比(m_(MC)/m_(CNT))制备的MC-CNT二元复合材料对电极的光电转换效率(PCE),进一步加入预先水热合成的CuS纳米材料,制备出MC-CNT-CuS三元复合材料对电极,同时探讨了CuS添加量和膜厚对对电极PCE的影响。实验结果表明,当m_(MC)/m_(CNT)=3/2时,2种碳材料能最大程度地发挥协同作用,使电池性能最好,PCE达12.69%。再加入0.4 g CuS时PCE可进一步提高,且对电极印刷5层时最优,此时所组装的电池获得的PCE最高(13.18%)。