基于单原子催化剂的光热催化转化：原理和应用

在以碳中和为目标的全球共识下,太阳能作为一种取之不竭用之不尽的绿色环保能源被认为是替代传统化石燃料最有潜力的方式。在各种太阳能转换技术中,光热催化不仅可以最大化利用太阳能,在光场和热场双重驱动力作用下,还可以显著提升化学反应速率,引起广泛的研究兴趣。以孤立的单个原子均匀分散在载体上形成的单原子催化剂具有100%原子利用率、优异的催化活性、热稳定性等优势。因此,将单原子催化剂应用于光热催化开始受到越来越多的关注。本综述介绍了光催化、热催化和光热催化的基本原理和特征,同时列举一些典型的例子。随后以不同载体作为分类标准,总结了单原子光热催化应用的前沿研究进展。最后,提出了该催化体系所面临的挑战和未来的发展方向。本文旨在全面了解单原子催化剂在太阳能驱动光热催化领域的研究现状并为未来发展提供可行的建议。     

The Synthesis of Single Crystals of Manganese Aluminophosphate Molecular Sieve and Studies on Their Properties

Single crystals of the molecular sieve, MnAPO-5, were synthesized by hydrothermal synthesis in the presence of fluoride ions. It was shown by X-ray diffraction, infrared spectroscopy, electron paramagnetic resonance spectroscopy, electron probe analysis and chemical composition analysis that the structure of MnAPO-5 is of the A1PO-5 type, and manganese(Ⅱ) is incorporated into the framework. Adsorption properties, thermal stability and surface acidity were also investigated.     

Near-infrared Aza-BODIPY Dyes Through Molecular Surgery for Enhanced Photothermal and Photodynamic Antibacterial Therapy

The widespread use of high-dose antibiotics will not only lead to the rapid acquisition of antibiotic resistance and increased incidence of drug-resistant bacterial infections, but also produce toxic side effects on normal tissues. Herein, two near-infrared dyes BDP-4PTZ and BDP-4DPA were synthesized, and the electron donors of diphenylamine and phenothiazine with the only difference of sulphur(S)-lock between the two phenyl rings were introduced onto the electron acceptor aza-dipyrromethene boron difluoride(aza-BODIPY) through molecular surgery. Through co-precipitation into nanoparticles(NPs), BDP-4PTZ NPs and BDP-4DPA NPs were fabricated with good biocompatibility. Upon 660 nm photoirradiation, BDP-4PTZ NPs and BDP-4DPA NPs showed excellent photothermal conversion efficiency(43% and 50%, respectively) and reactive oxygen species(ROS) production performance(ca. 3.6 and 6 times higher than that of indocyanine green, respectively). In vitro antibacterial experiments indicated that both NPs could effectively destroy the bacteria's membrane to eradicate drug-resistant bacteria. Furthermore, the bacterial abscess was effectively eliminated after treatment with BDP-4DPA NPs under 660 nm photoirradiation without adverse effects. Thus, through molecular surgery, BDP-4DPA without the S-lock demonstrates synergistic photothermal and photodynamic antimicrobial activities, which is promising for further molecular design towards effective neo-antimicrobial phototherapy.     

High Strength Electrospun Single Copolyacrylonitrile (coPAN) Nanofibers with Improved Molecular Orientation by Drawing

High-performance carbon nanofibers are highly dependent on the performance of their precursors, especially polyacrylonitrile (PAN).In this work, the copolymer of PAN (coPAN) was synthesized for electrospinning. A self-assembling set-up was used for the stretching of single coPAN nanofibers. FTIR and Raman spectroscopies were used to characterize the chemical structure of coPAN nanofibers. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to monitor the morphology of single coPAN nanofibers under different drawing times. Micro-tensile test was used to determine the mechanical properties of single coPAN nanofibers. The results indicated that the drawing led to an increase in degree of molecular orientation along the fiber axis from 0.656 to 0.808, tensile strength from 304 MPa to 595 MPa, and modulus from 3.1 GPa to 12.4 GPa. This research would provide fundamental information of high-performance electrospun coPAN nanofibers and offer opportunities for the preparation of high-performance carbon nanofibers.     

Diradicaloid Boron-Doped Molecular Carbons Achieved by Pentagon-Fusion

Molecular carbons (MCs) are molecular cutouts of carbon materials. Doping with heteroatoms and constructing open-shell structures are two powerful approaches to achieve unexpected and unique properties of MCs. Herein, we disclose a new strategy to design open-shell boron-doped MCs (BMCs), namely by pentagon-fusion of an organoborane π-system. We synthesized two diradicaloid BMC molecules that feature C₂₄B and C₃₈B π-skeletons containing a pentagonal ring. A thorough investigation reveals that such pentagon-fusion not only leads to their local antiaromaticity, but also incorporates an internal quinoidal substructure and thereby induces open-shell singlet diradical states. Moreover, their fully fused structures enable efficient π conjugation, which is expanded over the whole frameworks. Consequently, some intriguing physical properties are achieved, such as narrow energy gaps, very broad light absorptions, and superior photothermal capability, along with excellent photostability. Notably, the solid of the C₃₈B molecule exhibits absorption that covers the range of 300–1200 nm and an efficiency of 93.5 % for solar-driven water evaporation, thus demonstrating the potential of diradicaloid BMCs as high-performance organic photothermal materials.     

Molecular Engineering of Corrole Radicals by Polycyclic Aromatic Fusion: Towards Open-Shell Near-Infrared Materials for Efficient Photothermal Therapy

Open-shell radicals are promising near-infrared (NIR) photothermal agents (PTAs) owing to their easily accessible narrow band gaps, but their stabilization and functionalization remain challenging. Herein, highly stable π-extended nickel corrole radicals with [4n+1] π systems are synthesized and used to prepare NIR-absorbing PTAs for efficient phototheranostics. The light-harvesting ability of corrole radicals gradually improves as the number of fused benzene rings on β-pyrrolic locations increases radially, with naphthalene- and anthracene-fused radicals and their one-electron oxidized [4n] π cations exhibiting panchromatic visible-to-NIR absorption. The extremely low doublet excited states of corrole radicals promote heat generation via nonradiative decay. By encapsulating naphthocorrole radicals with amphiphilic polymer, water-soluble nanoparticles Na-NPs are produced, which exhibit outstanding photostability and high photothermal conversion efficiency of 71.8 %. In vivo anti-tumor therapy results indicate that Na-NPs enable photoacoustic imaging of tumors and act as biocompatible PTAs for tumor ablation when triggered by 808 nm laser light. The “aromatic-ring fusion” strategy for energy-gap tuning of corrole radicals opens a new platform for developing robust NIR-absorbing photothermal materials.     

Switching Quantum Interference in Single-Molecule Junctions by Mechanical Tuning

The charge transport through single-molecule electronic devices can be controlled mechanically by changing the molecular geometrical configuration in situ, but the tunable conductance range is typically less than two orders of magnitude. Herein, we proposed a new mechanical tuning strategy to control the charge transport through the single-molecule junctions via switching quantum interference patterns. By designing molecules with multiple anchoring groups, we switched the electron transport between the constructive quantum interference (CQI) pathway and the destructive quantum interference (DQI) pathway, and more than four orders of magnitude conductance variation can be achieved by shifting the electrodes in a range of about 0.6 nm, which is the highest conductance range ever achieved using mechanical tuning.     

单分子电导测量技术及其影响因素

Molecular electronics is an important field for the application of nanotechnologies with an ultimate goal of building functional devices using single molecules or molecular arrays to realize the same functionality as macroscopic devices. To attain this goal, reliable techniques for measuring and manipulating electron transfer processes through single molecules are essential. There are various techniques and many environmental factors influencing single-molecule electronic conductance measurements. In this review, we first provide a detailed introduction and classification of the current well-accepted techniques in this field for measuring single-molecule conductance. All available techniques are summarized into two categories: the fixed junction technique and break junction technique. The break junction technique involves repeatedly forming and breaking molecular junctions by mechanically controlling a pair of electrodes moving into and out of contact in the presence of target molecules. Single-molecule conductance can be determined from the conductance plateaus that appear in typical conductance decay traces when molecules bind two electrodes during their separation process. In contrast, the fixed junction technique is to fix the distance between a pair of electrodes and measure the conductance fluctuations when a single molecule binds the two electrodes stochastically. Both techniques comprise different application methods and have been employed preferentially by different groups. Specific features of both techniques and their intrinsic advantages are compared and summarized in Section 4.     

pH-Triggered Molecular Switch Toward Texture-Regulated Zn Anode

Zn electrodes in aqueous media exhibit an unstable Zn/electrolyte interface due to severe parasitic reactions and dendrite formation. Here, a dynamic Zn interface modulation based on the molecular switch strategy is reported by hiring γ-butyrolactone (GBL) in ZnCl₂/H₂O electrolyte. During Zn plating, the increased interfacial alkalinity triggers molecular switch from GBL to γ-hydroxybutyrate (GHB). GHB strongly anchors on Zn surface via triple Zn−O bonding, leading to suppressive hydrogen evolution and texture-regulated Zn morphology. Upon Zn stripping, the fluctuant pH turns the molecular switch reaction off through the cyclization of GHB to GBL. This dynamic molecular switch strategy enables high Zn reversibility with Coulombic efficiency of 99.8 % and Zn||iodine batteries with high-cyclability under high Zn depth of discharge (50 %). This study demonstrates the importance of dynamic modulation for Zn electrode and realizes the reversible molecular switch strategy to enhance its reversibility.     

Reversible Switching CuII/CuI Single Sites Catalyze High-rate and Selective CO2 Photoreduction

Herein, we first design a model of reversible redox-switching metal–organic framework single-unit-cell sheets, where the abundant metal single sites benefit for highly selective CO₂ reduction, while the reversible redox-switching metal sites can effectively activate CO₂ molecules. Taking the synthetic Cu-MOF single-unit-cell sheets as an example, synchrotron-radiation quasi in situ X-ray photoelectron spectra unravel the reversible switching Cu^II/Cu^I single sites initially accept photoexcited electrons and then donate them to CO₂ molecules, which favors the rate-liming activation into CO₂^δ−, verified by in situ FTIR spectra and Gibbs free energy calculations. As an outcome, Cu-MOF single-unit-cell sheets achieve near 100 % selectivity for CO₂ photoreduction to CO with a high rate of 860 μmol g⁻¹ h⁻¹ without any sacrifice reagent or photosensitizer, where both the activity and selectivity outperform previously reported photocatalysts evaluated under similar conditions.     

Synthesis and Characterization of AlPO4-11 and MAPO-11 Single Crystals

The preparation of two types of molecular sieves AlPO4-11 and MAPO-11 is reported. The particle size of the latter is hundreds of microns, about 10 times larger than that of the former. The XRD, IR and DTA spectra have demonstrated that magnesium has been introduced into the framework of AlPO4-11. The successful preparation of large single crystal of MAPO-11 will open up a new area for the preparation of large molecular sieves crystals in the future. The large MAPO-11 crystal compound is a promising host for the host-guest assembly of composite materials.     

SPONGE:A GPU-Accelerated Molecular Dynamics Package with Enhanced Sampling and AI-Driven Algorithms

SPONGE(Simulation Package tOward Next GEneration molecular modeling)is a software package for molecular dynamics(MD)simulation of solution and surface molecular systems.In this version of SPONGE,the all-atom potential energy functions used in AMBER MD packages are used by default and other all-atom/coarse-grained potential energy functions are also supported.SPONGE is designed to extend the timescale being approached in MD simulations by utilizing the latest CUDA-enabled graphical processing units(GPU)and adopting highly efficient enhanced sampling algorithms,such as integrated tempering,selective integrated tempering and enhanced sampling of reactive trajectories.It is highly modular and new algorithms and functions can be incorporated con veniently.Particularly,a specialized Python plugin can be easily used to perform the machine learning MD simulation with MindSpore,TensorFlow,PyTorch or other popular machine learning frameworks.Furthermore,a plugin of Finite-Element Method(FEM)is also available to handle metallic surface systems.All these advanced features increase the power of SPONGE for modeling and simulation of complex chemical and biological systems.     

Symmetry and Rigidity for Boosting Erbium-Based Molecular Light-Upconversion in Solution

Previously limited to highly symmetrical homoleptic triple-helical complexes [Er( Lk )₃]³⁺, where Lk are polyaromatic tridentate ligands, single-center molecular-based upconversion using linear optics and exploiting the excited-state absorption mechanism (ESA) greatly benefits from the design of stable and low-symmetrical [ Lk Er(hfa)₃] heteroleptic adducts (hfa⁻=hexafluoroacetylacetonate anion). Depending on (i) the extended π-electron delocalization, (ii) the flexibility and (iii) the heavy atom effect brought by the bound ligand Lk , the near-infrared (801 nm) to visible green (542 nm) upconversion quantum yield measured for [ Lk Er(hfa)₃] in solution at room temperature can be boosted by up to three orders of magnitude.     

Linear Adsorption Enables NO Selective Electroreduction to Hydroxylamine on Single Co Sites

Hydroxylamine (NH₂OH), a vital industrial feedstock, is presently synthesized under harsh conditions with serious environmental and energy concerns. Electrocatalytic nitric oxide (NO) reduction is attractive for the production of hydroxylamine under ambient conditions. However, hydroxylamine selectivity is limited by the competitive reaction of ammonia production. Herein, we regulate the adsorption configuration of NO by adjusting the atomic structure of catalysts to control the product selectivity. Co single-atom catalysts show state-of-the-art NH₂OH selectivity from NO electroreduction under neutral conditions (FE : 81.3 %), while Co nanoparticles are inclined to generate ammonia (FE : 92.3 %). A series of in situ characterizations and theoretical simulations unveil that linear adsorption of NO on isolated Co sites enables hydroxylamine formation and bridge adsorption of NO on adjacent Co sites induces the production of ammonia.     

Imaging of Single Molecular Behaviors Under Bifurcated Three-Centered Hydrogen Bonding

The mechanism for interaction and bonding of single guest molecules with active sites fundamentally determines the sorption and subsequent catalytic processes occurring in host zeolitic frameworks. However, no real-space studies on these significant issues have been reported thus far, since atomically visualizing guest molecules and recognizing single Al T-sites in zeolites remain challenging. Here, we atomically resolved single thiophene probes interacting with acid T-sites in the ZSM-5 framework to study the bonding behaviors between them. The synergy of bifurcated three-centered hydrogen bonds and van der Waals interactions can “freeze” the near-horizontal thiophene and make it stable enough to be imaged. By combining the imaging results with simulations, direct atomic observations enabled us to precisely locate the single Al T-sites in individual straight channels. Then, we statistically found that the thiophene bonding probability of the T11 site is 15 times higher than that of the T6 site. For different acid T-sites, the variation in the interaction synergy changes the inner angle of the host–guest O−H⋅⋅⋅S hydrogen bond, thereby affecting the stability of the near-horizontal thiophene and leading to considerable bonding inhomogeneities.     

Coding Intrinsic Disorder into DNA Hybridization Probes Enables Discrimination of Single Nucleotide Variants over Wide and Tunable Temperature Ranges

DNA hybridization probes are commonly used tools to discriminate clinically important single nucleotide variants (SNVs) but often work at elevated temperatures with very narrow temperature intervals (ΔT). Herein, we investigated the thermodynamic basis of the narrow ΔT both in silico and experimentally. Our study revealed that the high entropy penalty of classic hybridization probe designs was the key attributor for the narrow ΔT. Guided by this finding, we further introduced an entropy-compensate probe (Sprobe) design by coding intrinsic disorder into a stem-loop hybridization probe. Sprobe expanded ΔT from less than 10 °C to over 30 °C. Moreover, both ΔT and the optimal reaction temperature can be fine-tuned by simply altering the length of the loop domain. Sprobe was clinically validated by analyzing EGFR L858R mutation in 36 pairs of clinical tumor tissue samples collected from lung cancer patients, which revealed 100 % clinical sensitivity and specificity. We anticipate that our study will serve as a general guide for designing thermal robust hybridization probes for clinical diagnostics.     

Oxidation-Reduction Molecular Junction Covalent Organic Frameworks for Full Reaction Photosynthesis of H2O2

The full reaction photosynthesis of H₂O₂ that can combine water-oxidation and oxygen-reduction without sacrificial agents is highly demanded to maximize the light-utilization and overcome the complex reaction-process of anthraquinone-oxidation. Here, a kind of oxidation-reduction molecular junction covalent-organic-framework (TTF-BT-COF) has been synthesized through the covalent-coupling of tetrathiafulvalene (photo-oxidation site) and benzothiazole (photo-reduction site), which presents visible-light-adsorption region, effective electron-hole separation-efficiency and photo-redox sites that enables full reaction generation of H₂O₂. Specifically, a record-high yield (TTF-BT-COF, ≈276 000 μM h⁻¹ g⁻¹) for H₂O₂ photosynthesis without sacrificial agents has been achieved among porous crystalline photocatalysts. This is the first work that can design oxidation-reduction molecular junction COFs for full reaction photosynthesis of H₂O₂, which might extend the scope of COFs in H₂O₂ production.     

SAPO—5分子筛的结构研究

用X射线单晶衍射方法测定了晶体尺寸为150μm×100μm的SAPO-5分子筛的晶体结构.结果表明,SAPO-5属六方晶系,空间群P_6cc,晶胞参数a=1.3802nm,c=0.8503nm,权重偏离因子R_w=0.043.F~-离子位于2个四元环中间.电子探针分析结果表明,硅只取代磷进入SAPO-5分子筛骨架.     

500微米沸石分子筛单晶的制备方法

介绍了20世纪如年代以来500μg以上的沸石分子筛单晶的六种制备方法，包括类区域融化法、植入晶种法、有机热合成法、块状原料溶解法、氟离子效应合成法和双硅源法。这些方法通过控制反应体系中晶核的形成数量，然后在这些极少数晶核的基础上培养出沸石分子筛大单晶。     

A Photo- and Thermo-Driven Azoarene-Based Circularly Polarized Luminescence Molecular Switch in a Liquid Crystal Host

The development of chiral optical active materials with switchable circularly polarized luminescence (CPL) signals remains a challenge. Here an azoarene-based circularly polarized luminescence molecular switch, (S, R, S)-switch 1 and (R, R, R)-switch 2 , are designed and prepared with an (R)-binaphthyl azo group as a chiral photosensitive moiety and two (S)- or (R)-binaphthyl fluorescent molecules with opposite or the same handedness as chiral fluorescent moieties. Both switches exhibit reversible trans/cis isomerization when irradiated by 365 nm UV light and 520 nm green light in solvent and liquid crystal (LC) media. In contrast with the control (R, R, R)-switch 2 , when switch 1 is doped into nematic LCs, polarization inversion and switching-off of the CPL signals are achieved in the resultant helical superstructure upon irradiation with 365 nm UV and 520 nm green light, respectively. Meanwhile, the fluorescence intensity of the system is basically unchanged during this switching process. In particular, these variations of the CPL signals could be recovered after heating, realizing the true sense of CPL reversible switching. Taking advantage of the unique CPL switching, the proof-of-concept for “a dual-optical information encryption system” based on the above CPL active material is demonstrated.