Fluorine-Boosted Kinetic and Selective Molecular Sieving of C6 Derivatives

Porous molecular sorbents have excellent selectivity towards hydrocarbon separation with energy saving techniques. However, to realize commercialization, molecular sieving processes should be faster and more efficient compared to extended frameworks. In this work, we show that utilizing fluorine to improve the hydrophobic profile of leaning pillararenes affords a substantial kinetic selective adsorption of benzene over cyclohexane (20 : 1 for benzene). The crystal structure shows a porous macrocycle that acts as a perfect match for benzene in both the intrinsic and extrinsic cavities with strong interactions in the solid state. The fluorinated leaning pillararene surpasses all reported organic molecular sieves and is comparable to the extended metal–organic frameworks that were previously employed for this separation such as UIO-66. Most importantly, this sieving system outperformed the well-known zeolitic imidazolate frameworks under low pressure, which opens the door to new generations of molecular sieves that can compete with extended frameworks for more sustainable hydrocarbon separation.     

Proton-Coupled Electron Transfer Aided Thermoelectric Energy Conversion and Storage

Low-grade heat is ubiquitous in the environment and its thermoelectric conversion by the ionic conductors remains a challenge because of the low efficiency and poor sustainability. Here we demonstrate that the thermoelectric performances can be boosted by combining the Soret effect of protons and proton-coupled electron transfer (PCET) reaction of benzoquinone and hydroquinone in hydrogels. An overall enhancement of thermopower (25.9 mV K⁻¹), power factor (5 mW m⁻¹ K⁻²), figure of merit (>2.4) and continuity of power output is achieved. Moreover, an energy-storage function can be achieved by the redox couple, and a retained power output of 27.7 %, or 14 mW m⁻² for more than 3 hours is obtained by the re-balance of PCET reactants in the hydrogel after the removal of the temperature gradient.     

Light-Fueled Transformations of a Dynamic Cage-Based Molecular System

In a chemical equilibrium, the formation of high-energy species—in a closed system—is inefficient due to microscopic reversibility. Here, we demonstrate how this restriction can be circumvented by coupling a dynamic equilibrium to a light-induced E/Z isomerization of an azobenzene imine cage. The stable E-cage resists intermolecular imine exchange reactions that would “open” it. Upon switching, the strained Z-cage isomers undergo imine exchange spontaneously, thus opening the cage. Subsequent isomerization of the Z-open compounds yields a high-energy, kinetically trapped E-open species, which cannot be efficiently obtained from the initial E-cage, thus shifting an imine equilibrium energetically uphill in a closed system. Upon heating, the nucleophile is displaced back into solution and an opening/closing cycle is completed by regenerating the stable all-E-cage. Using this principle, a light-induced cage-to-cage transformation is performed by the addition of a ditopic aldehyde.     

Artificial Molecular Ratchets: Tools Enabling Endergonic Processes

Non-equilibrium chemical systems underpin multiple domains of contemporary interest, including supramolecular chemistry, molecular machines, systems chemistry, prebiotic chemistry, and energy transduction. Experimental chemists are now pioneering the realization of artificial systems that can harvest energy away from equilibrium. In this tutorial Review, we provide an overview of artificial molecular ratchets: the chemical mechanisms enabling energy absorption from the environment. By focusing on the mechanism type—rather than the application domain or energy source—we offer a unifying picture of seemingly disparate phenomena, which we hope will foster progress in this fascinating domain of science.     

Macrocycle-Based Crystalline Supramolecular Assemblies Built with Intermolecular Charge-Transfer Interactions

Synthetic macrocycles have served as principal tools for supramolecular chemistry, have greatly extended the scope of organic charge transfer (CT) complexes, and have proved to be of great practical value in the solid state during the past few years. In this Minireview, we summarize the research progress on the macrocycle-based crystalline supramolecular assemblies primarily driven by intermolecular CT interactions (a.k.a. macrocycle-based crystalline CT assemblies, MCCAs for short), which are classified by their donor–acceptor (D-A) constituent elements, including simplex macrocyclic hosts, heterogeneous macrocyclic hosts, and host–guest D-A pairs. Particular attention will be focused on their diverse functions and applications, as well as the underlying CT mechanisms from the perspective of crystal engineering. Finally, the remaining challenges and prospects are outlined.     

A Supramolecular Naphthalene Diimide Radical Anion with Efficient NIR-II Photothermal Conversion for E. coli-Responsive Photothermal Therapy

We report a supramolecular naphthalene diimide (NDI) radical anion with efficient NIR-II photothermal conversion for E. coli-responsive photothermal therapy. The supramolecular radical anion (NDI-2CB[7])⋅⁻, which is obtained from the E. coli-induced in situ reduction of NDI-2CB[7] neutral complex, formed by the host–guest interaction between an NDI derivative and cucurbit[7]uril (CB[7]), exhibits unexpectedly strong NIR-II absorption and remarkable photothermal conversion capacity in aqueous solution. The NIR-II absorption is caused by the self-assembly of NDI radical anions to form supramolecular dimer radicals in aqueous solution, which is supported by theoretically predicted spectra. The (NDI-2CB[7])⋅⁻ demonstrates excellent NIR-II photothermal antimicrobial activity (>99 %). This work provides a new approach for constructing NIR-II photothermal agents and non-contact treatments for bacterial infections.     

Investigating the Role of Vacancies on the Thermoelectric Properties of EuCuSb-Eu2ZnSb2 Alloys

AMX compounds with the ZrBeSi structure tolerate a vacancy concentration of up to 50 % on the M-site in the planar MX-layers. Here, we investigate the impact of vacancies on the thermal and electronic properties across the full EuCu_1−xZn_0.5xSb solid solution. The transition from a fully-occupied honeycomb layer (EuCuSb) to one with a quarter of the atoms missing (EuZn_0.5Sb) leads to non-linear bond expansion in the honeycomb layer, increasing atomic displacement parameters on the M and Sb-sites, and significant lattice softening. This, combined with a rapid increase in point defect scattering, causes the lattice thermal conductivity to decrease from 3 to 0.5 W mK⁻¹ at 300 K. The effect of vacancies on the electronic properties is more nuanced; we see a small increase in effective mass, large increase in band gap, and decrease in carrier concentration. Ultimately, the maximum zT increases from 0.09 to 0.7 as we go from EuCuSb to EuZn_0.5Sb.     

分子烙印技术的应用与最新进展

分子烙印技术是合成对模板分子具有特定识别能力的聚合物的技术。在第一届分子烙印技术国际会议报告文集的基础上对117篇文献进行了综述。总结了最近分子烙印技术在对映体或立体异构体分离、固相萃取、化学传感器和模拟生物传感器及催化生物反应工程方面取得的成绩和存在的问题。扼要介绍了在分子烙印技术发展过程中出现的新方法、新用途，指明了分子烙印技术的发展趋势。     

Room-Temperature High-Performance Thermoelectric Bi0.6Sb0.4Te: Elimination of Detrimental Band Inversion in BiTe

Room-temperature thermoelectric materials are the key to miniaturizing refrigeration equipment and have great scientific and social implications, yet their application is hindered by their extreme scarcity. BiTe exhibiting strong spin-orbit coupling peaks ZT at 600 K. Herein, we discover the synergy effect of Sb doping in BiTe that eliminates the detrimental band inversion and leads to an overlap of conduction band (CB) and valence band that significantly increases the S from 33 to 124 μV K⁻¹. In addition, this effect enhances the μ from 58 to 92 cm² V⁻¹ s⁻¹ owing to the sharp increase in the CB slope along the Γ-A in the first Brillouin zone. Furthermore, Sb doping increases the anharmonicity, shortens the phonon lifetime and lowers κ_lat. Finally, Se/Sb codoping further optimizes the ZT to 0.6 at 300 K, suggesting that Bi_0.6Sb_0.4Te_1−ySe_y is a potential room-temperature TE material.     

Insights into the Correlation of Cross-linking Modes with Mechanical Properties for Dynamic Polymeric Networks

Simultaneously introducing covalent and supramolecular cross-links into one system to construct dually cross-linked networks, has been proved an effective approach to prepare high-performance materials. However, so far, features and advantages of dually cross-linked networks compared with those possessing individual covalent or supramolecular cross-linking points are rarely investigated. Herein, on the basis of comparison between supramolecular polymer network (SPN), covalent polymer network (CPN) and dually cross-linked polymer network (DPN), we reveal that the dual cross-linking strategy can endow the DPN with integrated advantages of CPN and SPN. Benefiting from the energy dissipative ability along with the dissociation of host–guest complexes, the DPN shows excellent toughness and ductility similar to the SPN. Meanwhile, the elasticity of covalent cross-links in the DPN could rise the structural stability to a level comparable to the CPN, exhibiting quick deformation recovery capacity. Moreover, the DPN has the strongest breaking stress and puncture resistance among the three, proving the unique property advantages of dual cross-linking method. These findings gained from our study further deepen the understanding of dynamic polymeric networks and facilitate the preparation of high-performance elastomeric materials.     

Ferroelectric Ionic Molecular Crystals with Significant Plasticity and a Low Melting Point: High Performance in Hot-Pressed Polycrystalline Plates and Melt-Grown Crystalline Sheets

Among ferroelectric crystals based on small molecules, plastic/ferroelectric crystals are currently receiving particular attention because they can be used as bulk polycrystals. Herein, we show that an ionic molecular ferroelectric crystal, guanidinium tetrafluoroborate, exhibits significant malleability and multiaxial ferroelectricity despite the absence of a plastic crystal phase. Powder samples of this crystal can be processed into transparent bulk crystalline plates either by press-forming or by melt-growing. The plates show high ferroelectric performance and related properties, demonstrating the largest hitherto reported spontaneous polarization for bulk polycrystals of small-molecule-based ferroelectrics. Owing to the ready availability of large-scale materials and processability into various bulk crystalline forms, this ferroelectric crystal represents a highly promising functional material that will boost research on diverse applications as bulk crystals.     

Macromolecule-Metal Nanoparticle Complexes for Novel Development of Information Technology and Energy Conversion

Summary: Macromolecule-metal nanoparticle complexes have achieved a great deal of attention from the researchers since the nanotechnology boom, because nanoparticles can be easily prepared by chemical reactions, often stabilized by complex formation with macromolecules, and can play important roles in the construction of nanostructured materials for novel technologies. Here I would like to introduce three typical examples which are going to be developed in our group and will be potentially applied to novel information and energy-conversion technology, i.e., super-high-density magnetic recording media, fast-responsive liquid-crystal display, and processable thermoelectric materials.     

Microscopical Structuring of Solids by Molecular Beam Epitaxy—Spatially Resolved Materials Synthesis

Interfaces and heterojunctions which are incorporated into a crystal in well-defined geometrical and spatial arrangements can lead to a structuring or engineering of (semiconducting) solids down to atomic dimensions. The electrical and optical properties are then defined locally, and phenomena related to extremely small dimensions (“quantum size effects”) become more important than the actual chemical properties of the materials used. The technique of molecular beam epitaxy allows an atomic layer-by-layer deposition in a two-dimensional growth process, and crystalline materials in alternating layers of arbitrary composition and only a few atomic layers thickness are formed. The synthesis of microscopically structured solids by molecular beam epitaxy affords access to a new class of materials with accurately tailored electrical, optical, magnetic, dielectric, mechanical etc. properties. The semiconductor and metal superlattices described in this article, which are made of alternating thin layers of two different materials, symbolize just the beginning of a new area of materials engineering on a molecular (or atomic) scale. This periodic modulation of the chemical composition normal to the surface imposes an artificial periodicity on the semiconductor or metal crystal, a periodicity of one or two orders of magnitude larger than its natural lattice spacing. The synthesis of other materials combinations, including semiconductor/metal, semiconductor/insulator, metal/insulator, polymers, and magnetic materials, with entirely different properties and for completely different applications will certainly follow. Finally, a large variety of desired combinations of elements can be selected, and even metastable compounds with novel exciting properties can be synthesized by molecular beam epitaxy.     

没食子酸丙酯印迹电化学传感器的构建及应用研究

以羧基化的多壁碳纳米管(MWCNT)为基底,通过酰胺化表面接枝聚乙烯亚胺(PEI)得到MWCNT-PEI复合物功能单体,进而以没食子酸丙酯(PG)为模板分子、乙二醇二缩水甘油醚为交联剂,制备了PG表面分子印迹聚合物,最后采用滴涂法在玻碳电极(GCE)表面构建PG分子印迹电化学传感器。通过循环伏安、电化学阻抗和差分脉冲伏安等手段对所构建传感器的导电性以及PG分子的线性响应、特异识别性、检测稳定性和重复性等进行了测试与表征。结果表明,传感器在PG浓度为1×10~(-8)～1×10~(-5)mol/L的范围内具有良好的线性关系,相关系数为0. 9964,检出限达2. 5×10~(-9)mol/L。此外,该传感器在实际样品中的PG回收率为95%～98%。     

Thermoelectric Properties and Stability of Nanocomposites Type I Clathrate Ba-Cu-Si with SiC

Thermoelectric (TE) materials attract interest for the capability of converting waste heat into electricity. Nanostructuring is considered as an effective approach to improve the conversion efficiency by reducing the lattice thermal conductivity. Nanostructured materials are metastable due to the high interface energy of grain boundaries, therefore they lose easily the nanostructure features during the thermal cycling at high temperatures, i.e., showing instabilities in TE properties. Here we show the structural/microstructural stability of type I clathrate nanocomposites in the Ba-Cu-Si system with SiC as the secondary phase. SiC has no influence on the crystal structure of the type I clathrate and very limited contributions to the grain size reduction and size-growth prevention during the ball milling and hot pressing processes, but stabilizes the TE properties during thermal cycling. A high bulk density and as low as possible contamination in nanocomposites are essential for high TE performance and high stability in nanostructured materials.     

SAPO-34分子筛催化丁烯转化制丙烯的研究

通过水热法合成SAPO-34分子筛,将其制成催化剂用于催化丁烯转化制取丙烯,考察了反应温度、空速和铝磷比等对催化性能的影响;还比较了SAPO-34分子筛与ZSM-5分子筛催化该反应的差异.结果表明,在实验范围内,反应温度升高会使得丁烯的转化率明显增高,且丙烯选择性提高;而空速增加,则丁烯的转化率和丙烯选择性降低;铝磷比越大,对丙烯的选择性越差.在有效的反应时间内,SAPO-34分子筛催化效果好于ZSM-5分子筛,但单程寿命较ZSM-5分子筛短.     

Inside Cover: Bending Actuation of Hydrogels through Rotation of Light-Driven Molecular Motors (Angew. Chem. Int. Ed. 13/2023)

The unidirectional rotation of chemically crosslinked light-driven molecular motors is shown to progressively shift the swelling equilibrium of hydrogels. The concentration of molecular motors and the initial strand density of the polymer network are key parameters to modulate the macroscopic contraction of the material, and both parameters can be tuned using polymer chains of different molecular weights. These findings led to the design of optimized hydrogels revealing a half-time contraction of approximately 5 min. Furthermore, under inhomogeneous stimulation, the local contraction event was exploited to design useful bending actuators with an energy output 400 times higher than for previously reported self-assembled systems involving rotary motors. In the present configuration, we measure that a single molecular motor can lift up loads of 200 times its own molecular weight.     

多模态分子影像技术在肿瘤诊断中的进展

多模态分子影像技术融合多种影像学检测手段的优势,为肿瘤诊断提供了更加全面而精确的信息,实现在细胞及分子水平对肿瘤进行及时的个性化诊断、动态定量监测等。本文介绍了多模态分子影像技术的基本概念、实现方式,以及近年来多模态分子影像技术在肿瘤诊断中的应用进展,并展望了其发展趋势。     

单嘧磺隆晶体-活性构象转换的分子动力学模拟

应用分子动力学模拟方法对单嘧磺隆在水、正辛醇和正辛烷3种不同溶剂中的构象行为、单嘧磺隆与3种溶剂之间的相互作用能及氢键相互作用进行了计算研究. 计算结果表明, 在3种不同的溶剂中, 单嘧磺隆的优势构象不同; 其构象转换过程, 特别是转换成活性构象的过程主要发生在水溶液中; 与溶剂分子间的相互作用是分子构象行为的决定因素; 单嘧磺隆的脲桥部分可以和含氢键接受体的溶剂形成氢键, 分子间与分子内氢键的竞争可能是从晶体构象转换成活性构象的主要驱动力.     

Molecular Engineering of a Metal-Organic Polymer for Enhanced Electrochemical Nitrate-to-Ammonia Conversion and Zinc Nitrate Batteries

Metal–organic framework-based materials are promising single-site catalysts for electrocatalytic nitrate (NO₃⁻) reduction to value-added ammonia (NH₃) on account of well-defined structures and functional tunability but still lack a molecular-level understanding for designing the high-efficient catalysts. Here, we proposed a molecular engineering strategy to enhance electrochemical NO₃⁻-to-NH₃ conversion by introducing the carbonyl groups into 1,2,4,5-tetraaminobenzene (BTA) based metal-organic polymer to precisely modulate the electronic state of metal centers. Due to the electron-withdrawing properties of the carbonyl group, metal centers can be converted to an electron-deficient state, fascinating the NO₃⁻ adsorption and promoting continuous hydrogenation reactions to produce NH₃. Compared to CuBTA with a low NO₃⁻-to-NH₃ conversion efficiency of 85.1 %, quinone group functionalization endows the resulting copper tetraminobenzoquinone (CuTABQ) distinguished performance with a much higher NH₃ FE of 97.7 %. This molecular engineering strategy is also universal, as verified by the improved NO₃⁻-to-NH₃ conversion performance on different metal centers, including Co and Ni. Furthermore, the assembled rechargeable Zn−NO₃⁻ battery based on CuTABQ cathode can deliver a high power density of 12.3 mW cm⁻². This work provides advanced insights into the rational design of metal complex catalysts through the molecular-level regulation for NO₃⁻ electroreduction to value-added NH₃.