Metal–Organic‐Framework‐Based Catalysts for Photoreduction of CO2

Photoreduction of CO₂ into reusable carbon forms is considered as a promising approach to address the crisis of energy from fossil fuels and reduce excessive CO₂ emission. Recently, metal–organic frameworks (MOFs) have attracted much attention as CO₂ photoreduction‐related catalysts, owing to their unique electronic band structures, excellent CO₂ adsorption capacities, and tailorable light‐absorption abilities. Recent advances on the design, synthesis, and CO₂ reduction applications of MOF‐based photocatalysts are discussed here, beginning with the introduction of the characteristics of high‐efficiency photocatalysts and structural advantages of MOFs. The roles of MOFs in CO₂ photoreduction systems as photocatalysts, photocatalytic hosts, and cocatalysts are analyzed. Detailed discussions focus on two constituents of pure MOFs (metal clusters such as Ti–O, Zr–O, and Fe–O clusters and functional organic linkers such as amino‐modified, photosensitizer‐functionalized, and electron‐rich conjugated linkers) and three types of MOF‐based composites (metal–MOF, semiconductor–MOF, and photosensitizer–MOF composites). The constituents, CO₂ adsorption capacities, absorption edges, and photocatalytic activities of these photocatalysts are highlighted to provide fundamental guidance to rational design of efficient MOF‐based photocatalyst materials for CO₂ reduction. A perspective of future research directions, critical challenges to be met, and potential solutions in this research field concludes the discussion.     

Bimetallic Metal‐Organic Frameworks: Probing the Lewis Acid Site for CO2 Conversion

A highly porous metal‐organic framework (MOF) incorporating two kinds of second building units (SBUs), i.e., dimeric paddlewheel (Zn₂(COO)₄) and tetrameric (Zn₄(O)(CO₂)₆), is successfully assembled by the reaction of a tricarboxylate ligand with Zn^II ion. Subsequently, single‐crystal‐to‐single‐crystal metal cation exchange using the constructed MOF is investigated, and the results show that Cu^II and Co^II ions can selectively be introduced into the MOF without compromising the crystallinity of the pristine framework. This metal cation‐exchangeable MOF provides a useful platform for studying the metal effect on both gas adsorption and catalytic activity of the resulted MOFs. While the gas adsorption experiments reveal that Cu^II and Co^II exchanged samples exhibit comparable CO₂ adsorption capability to the pristine Zn^II‐based MOF under the same conditions, catalytic investigations for the cycloaddition reaction of CO₂ with epoxides into related carbonates demonstrate that Zn^II‐based MOF affords the highest catalytic activity as compared with Cu^II and Co^II exchanged ones. Molecular dynamic simulations are carried out to further confirm the catalytic performance of these constructed MOFs on chemical fixation of CO₂ to carbonates. This research sheds light on how metal exchange can influence intrinsic properties of MOFs.     

Two-dimensional d-πconjugated metal-organic framework based on hexahydroxytrinaphthylene

The development of new two-dimensional(2D)d-πconjugated metal-organic frameworks(MOFs)holds great promise for the construction of a new generation of porous and semiconductive materials.This paper describes the synthesis,structural characterization,and electronic properties of a new d-πconjugated 2D MOF based on the use of a new ligand 2,3,8,9,14,15-hexahydroxytrinaphthylene.The reticular self-assembly of this largeπ-conjugated organic building block with Cu(II)ions in a mixed solvent system of 1,3-dimethyl-2-imidazolidinone(DMI)and H2 O with the addition of ammonia water or ethylenediamine leads to a highly crystalline MOF Cu3(HHTN)2,which possesses pore aperture of 2.5 nm.Cu3(HHTN)2 MOF shows moderate electrical conductivity of 9.01×10^-8S·cm^-1at 385 K and temperature-dependent band gap ranging from 0.75 to 1.65 eV.After chemical oxidation by l2,the conductivity of Cu3(HHTN)2 can be increased by 360 times.This access to HHTN based MOF adds an important member to previously reported MOF systems with hexagonal lattice,paving the way towards systematic studies of structure-property relationships of semiconductive MOFs.     

Two novel Zn (II)​-based metal–organic frameworks for rapidly selective adsorption and efficient photocatalytic degradation of hazardous aromatic dyes in aqueous phase

Two novel Zn-MOFs constructed from 5-hydroxy-2-nitroisophthalic acid (H₂DIPA) and 5-(4-carboxy-2-nitrophenoxy)-2-nitroisophthalic acid (H₃BPPA), namely: {[Zn₂(DIPA)₂(bimp)₅]·DMF·2H₂O}_n (Zn-MOF 1), {[Zn₂(HBPPA)₂(bibp)₂]·2H₂O}_n (Zn-MOF 2) (bimp = 1,4-di(1H-imidazol-1-yl)butane, bibp = 4,4′-bis(imidazolyl) biphenyl), have been synthesized under solvothermal conditions and characterized by single crystal X-ray diffraction, elemental analysis, IR spectra, powder X-ray diffraction (PXRD) and thermogravimetric analysis (TG). The single-crystal X-ray diffraction analysis indicates that Zn-MOF 1 exhibits an uncommon 3-nodal framework with a (4·6·8)(4·6³·8²)(6⁶) topology, whereas Zn-MOF 1 exhibits an uninodal 4-connected framework with a (4⁴·6²) topology. Moreover, both of the two Zn-MOFs exhibit exceptional dye adsorption capacities towards the organic dyes with high adsorption rates and excellent adsorption amounts. Particularly, Zn-MOF 1 can selectively adsorb the cationic dye malachite green (MG) whereas Zn-MOF 2 adsorb the anionic dye methyl orange (MO) when there exists another kind of dye in the system. The adsorption process can be illustrated by pseudo-second order kinetic and Langmuir isotherm, and the feasible adsorption mechanism could be the electrostatical interactions, hydrogen bonding between the MOFs and the dyes. Meanwhile, the two Zn-MOFs also show good photocatalytic degradation capabilities toward MB/MV dyes under UV irradiation, and the mechanism studies demonstrate that the main active species are ·OH radicals. Therefore, this functional MOF materials can be treated as a convenient and cost-efficient solution for the sewage handling and environmental protection.     

Enhanced the Efficiency of Electrocatalytic CO2-to-CO Conversion by Cd Species Anchored into Metal-Organic Framework

Metal-organic frameworks (MOFs) as a promising platform for electrocatalytic CO₂ conversion are still restricted by the low efficiency or unsatisfied selectivity for desired products. Herein, zirconium-based porphyrinic MOF hollow nanotubes with Cd sites (Cd-PCN-222HTs) are reported for electrocatalytic CO₂-to-CO conversion. The dispersed Cd species are anchored in PCN-222HTs and coordinated by N atoms of porphyrin structures. It is discovered that Cd-PCN-222HTs have glorious electrocatalytic activity for selective CO production in ionic liquid-water (H₂O)-acetonitrile (MeCN) electrolyte. The CO Faradaic efficiency (FE_CO) of >80% could be maintained in a wide potential range from −2.0 to −2.4 V versus Ag/Ag⁺, and the maximum current density could reach 68.0 mA cm⁻² at −2.4 V versus Ag/Ag⁺ with a satisfied turnover frequency of 26 220 h⁻¹. The enhanced efficiency of electrocatalytic CO₂ conversion of Cd-PCN-222HTs is closely related to its hollow structure, anchored Cd species, and good synergistic effect with electrolyte. The density functional theory calculations indicate that the dispersed Cd sites anchored in PCN-222HTs not only favor the formation of *COOH intermediate but also hinder the hydrogen evolution reaction, resulting in high activity of electrocatalytic CO₂-to-CO conversion.     

The Effect of Materials Architecture in TiO2/MOF Composites on CO2 Photoreduction and Charge Transfer

CO₂ photoreduction to C₁/C₁₊ energized molecules is a key reaction of solar fuel technologies. Building heterojunctions can enhance photocatalysts performance, by facilitating charge transfer between two heterojunction phases. The material parameters that control this charge transfer remain unclear. Here, it is hypothesized that governing factors for CO₂ photoreduction in gas phase are: i) a large porosity to accumulate CO₂ molecules close to catalytic sites and ii) a high number of “points of contact” between the heterojunction components to enhance charge transfer. The former requirement can be met by using porous materials; the latter requirement by controlling the morphology of the heterojunction components. Hence, composites of titanium oxide or titanate and metal–organic framework (MOF), a highly porous material, are built. TiO₂ or titanate nanofibers are synthesized and MOF particles are grown on the fibers. All composites produce CO under UV–vis light, using H₂ as reducing agent. They are more active than their component materials, e.g., ≈9 times more active than titanate. The controlled composites morphology is confirmed and transient absorption spectroscopy highlights charge transfer between the composite components. It is demonstrated that electrons transfer from TiO₂ into the MOF, and holes from the MOF into TiO₂, as the MOF induces band bending in TiO₂.     

Customizing Metal-Organic Frameworks by Lego-Brick Strategy for One-Step Purification of Ethylene from a Quaternary Gas Mixture

One-step purification of ethylene (C₂H₄) from a quaternary gas mixture of C₂H₆/C₂H₄/C₂H₂/CO₂ by adsorption is a promising separation process, yet developing adsorbents that synergistically capture various gas impurities remains challenging. Herein, a Lego-brick strategy is proposed to customize pore chemistry in a unified framework material. The ethane-selective MOF platform is further modified with customized binding sites to specifically adsorb acetylene and carbon dioxide, thus one-step purification of C₂H₄ with high productivity of polymer-grade product (134 mol kg⁻¹) is achieved on the assembly of porous coordination polymer-2,5-furandicarboxylic acid (PCP-FDCA) and PCP-5-aminoisophthalic acid (IPA-NH₂). Computational studies verify that the low-polarity surface of this MOFs-based platform provides a delicate environment for C₂H₆ recognition, and the specific binding sites (FDCA and IPA-NH₂) exhibit favorable trapping of C₂H₂ and CO₂ via C H^δ+···O^δ− and C^δ+···N^δ− electrostatic interactions, respectively. The proposed Lego-brick strategy to customize binding sites within the MOFs structure provides new ideas for the design of adsorbents for compounded separation tasks.     

Strain-Engineering of Mesoporous Cs3Bi2Br9/BiVO4 S-Scheme Heterojunction for Efficient CO2 Photoreduction

Slow charge kinetics and unfavorable CO₂ adsorption/activation strongly inhibit CO₂ photoreduction. In this study, a strain-engineered Cs₃Bi₂Br₉/hierarchically porous BiVO₄ (s-CBB/HP-BVO) heterojunction with improved charge separation and tailored CO₂ adsorption/activation capability is developed. Density functional theory calculations suggest that the presence of tensile strain in Cs₃Bi₂Br₉ can significantly downshift the p-band center of the active Bi atoms, which enhances the adsorption/activation of inert CO₂. Meanwhile, in situ irradiation X-ray photoelectron spectroscopy and electron spin resonance confirm that efficient charge transfer occurs in s-CBB/HP-BVO following an S-scheme with built-in electric field acceleration. Therefore, the well-designed s-CBB/HP-BVO heterojunction exhibits a boosted photocatalytic activity, with a total electron consumption rate of 70.63 µmol g⁻¹ h⁻¹, and 79.66% selectivity of CO production. Additionally, in situ diffuse reflectance infrared Fourier transform spectroscopy reveals that CO₂ photoreduction undergoes a formaldehyde-mediated reaction process. This work provides insight into strain engineering to improve the photocatalytic performance of halide perovskite.     

Water-Stable Fluorous Metal–Organic Frameworks with Open Metal Sites and Amine Groups for Efficient Urea Electrocatalytic Oxidation

Urea oxidation reaction (UOR) is one of the promising alternative anodic reactions to water oxidation that has attracted extensive attention in green hydrogen production. The application of specifically designed electrocatalysts capable of declining energy consumption and environmental consequences is one of the major challenges in this field. Therefore, the goal is to achieve a resistant, low-cost, and environmentally friendly electrocatalyst. Herein, a water-stable fluorinated Cu(II) metalorganic framework (MOF) {[Cu₂(L)(H₂O)₂]·(5DMF)(4H₂O)}_n (Cu-FMOF-NH₂; H₄L = 3,5-bis(2,4-dicarboxylic acid)-4-(trifluoromethyl)aniline) is developed utilizing an angular tetracarboxylic acid ligand that incorporates both trifluoromethyl (–CF₃) and amine (–NH₂) groups. The tailored structure of Cu-FMOF-NH₂ where linkers are connected by fluoride bridges and surrounded by dicopper nodes reveals a 4,24T1 topology. When employed as electrocatalyst, Cu-FMOF-NH₂ requires only 1.31 V versus reversible hydrogen electrode (RHE) to deliver 10 mA cm⁻² current density in 1.0 m KOH with 0.33 m urea electrolyte and delivered an even higher current density (50 mA cm⁻²) at 1.47 V versus RHE. This performance is superior to several reported catalysts including commercial RuO₂ catalyst with overpotential of 1.52 V versus RHE. This investigation opens new opportunities to develop and utilize pristine MOFs as a potential electrocatalyst for various catalytic reactions.     

Specific K+ Binding Sites as CO2 Traps in a Porous MOF for Enhanced CO2 Selective Sorption

Metal–organic frameworks (MOFs) can be fine‐tuned to boost sorbent‐sorbate interactions in order to improve gas sorption and separation performance, but the design of MOFs with ideal structural features for gas separation applications remains a challenge. Herein it is reported that unsaturated alkali metal sites can be immobilized in MOFs through a tetrazole based motif and that gas affinity can thereby be boosted. In the prototypal MOF of this type‐ NKU‐521 (NKU denotes Nankai University), K⁺ cations are effectively embedded in a trinuclear Co²⁺‐tetrazole coordination motif. The embedded K⁺ sites are exposed to the pores of NKU‐521 through water removal, and the isosteric heat (Q_st) for CO₂ is boosted to 41 kJ mol^‐1. The nature of the binding site is validated by molecular simulations and structural characterization. The K⁺ cations in effect serve as gas traps and boost the CO₂‐framework affinity, as measured by the Q_st, by 24%. In addition, the impact of unsaturated alkali metal sites upon the separation of hydrocarbons is evaluated for the first time in MOFs using ideal adsorbed solution theory (IAST) calculations and column breakthrough experiments. The results reveal that the presence of exposed K⁺ sites benefits gas sorption and hydrocarbon separation performances of this MOF.     

Nanoscale Janus Z-Scheme Heterojunction for Boosting Artificial Photosynthesis

Artificial photosynthesis for CO₂ reduction coupled with water oxidation currently suffers from low efficiency due to inadequate interfacial charge separation of conventional Z-scheme heterojunctions. Herein, an unprecedented nanoscale Janus Z-scheme heterojunction of CsPbBr₃/TiO_x is constructed for photocatalytic CO₂ reduction. Benefitting from the short carrier transport distance and direct contact interface, CsPbBr₃/TiO_x exhibits significantly accelerated interfacial charge transfer between CsPbBr₃ and TiO_x (8.90 × 10⁸ s⁻¹) compared with CsPbBr₃:TiO_x counterpart (4.87 × 10⁷ s−¹) prepared by traditional electrostatic self-assembling. The electron consumption rate of cobalt doped CsPbBr₃/TiO_x can reach as high as 405.2 ± 5.6 µmol g⁻¹ h⁻¹ for photocatalytic CO₂ reduction to CO coupled with H₂O oxidation to O₂ under AM1.5 sunlight (100 mW cm⁻²), over 11-fold higher than that of CsPbBr₃:TiO_x, and surpassing the reported halide-perovskite-based photocatalysts under similar conditions. This work provides a novel strategy to boost charge transfer of photocatalysts for enhancing the performance of artificial photosynthesis.     

Utilizing Metal-Thiocatecholate Functionalized UiO-66 Framework for Photocatalytic Hydrogen Evolution Reaction

Exploiting clean energy is essential for sustainable development and sunlight-driven photocatalytic water splitting represents one of the most promising approaches toward this goal. Metal-organic frameworks (MOFs) are competent photocatalysts owing to their tailorable functionality, well-defined structure, and high porosity. Yet, the introduction of the unambiguous metal-centered active site into MOFs is still challenging since framework motifs capable of anchoring metal ions firmly are lacking. Herein, the assembly using 1,4-dicarboxylbenzene-2,3-dithiol (H₂ dcbdt ) and Zr-Oxo clusters to give a thiol-functionalized UiO-66 type framework,  UiO-66-dcbdt, is reported. The thiocatechols on the struts are allowed to capture transition metal (TM) ions to generate  UiO-66-dcbdt-M  ( M   = Fe, Ni, Cu) with unambiguous metal-thiocatecholate moieties for photocatalytic hydrogen evolution reaction (HER).  UiO-66-dcbdt-Cu  is found the best catalyst exhibiting an HER rate of 4.18 mmol g⁻¹ h⁻¹ upon irradiation with photosensitizing Ru-polypyridyl complex. To skip the use of the external sensitizer,  UiO-66-dcbdt-Cu  is heterojunctioned with titanium dioxide (TiO₂) and achieves an HER rate of 12.63 mmol g⁻¹ h⁻¹ (32.3 times that of primitive TiO₂). This work represents the first example of MOF assembly employing H₂ dcbdt  as the mere linker followed by chelation with TM ions and undoubtedly fuels the rational design of MOF photocatalysts bearing well-defined active sites.     

Metal-Organic Frameworks for Greenhouse Gas Applications

Using petrol to supply energy for a car or burning coal to heat a building generates plenty of greenhouse gas (GHG) emissions, including carbon dioxide (CO₂), water vapor (H₂O), methane (CH₄), nitrous oxide (N₂O), ozone (O₃), fluorinated gases. These up-and-coming metal-organic frameworks (MOFs) are structurally endowed with rigid inorganic nodes and versatile organic linkers, which have been extensively used in the GHG-related applications to improve the lives and protect the environment. Porous MOF materials and their derivatives have been demonstrated to be competitive and promising candidates for GHG separation, storage and conversions as they shows facile preparation, large porosity, adjustable nanostructure, abundant topology, and tunable physicochemical property. Enormous progress has been made in GHG storage and separation intrinsically stemmed from the different interaction between guest molecule and host framework from MOF itself in the recent five years. Meanwhile, the use of porous MOF materials to transform GHG and the influence of external conditions on the adsorption performance of MOFs for GHG are also enclosed. In this review, it is also highlighted that the existing challenges and future directions are discussed and envisioned in the rational design, facile synthesis and comprehensive utilization of MOFs and their derivatives for practical applications.     

Single-Site Metal–Organic Framework and Copper Foil Tandem Catalyst for Highly Selective CO2 Electroreduction to C2H4

Tandem catalysis is a promising way to break the limitation of linear scaling relationship for enhancing efficiency, and the desired tandem catalysts for electrochemical CO₂ reduction reaction (CO₂RR) are urgent to be developed. Here, a tandem electrocatalyst created by combining Cu foil (CF) with a single-site Cu(II) metal–organic framework (MOF), named as Cu–MOF–CF, to realize improved electrochemical CO₂RR performance, is reported. The Cu–MOF–CF shows suppression of CH₄, great increase in C₂H₄ selectivity (48.6%), and partial current density of C₂H₄ at −1.11 V versus reversible hydrogen electrode. The outstanding performance of Cu–MOF–CF for CO₂RR results from the improved microenvironment of the Cu active sites that inhibits CH₄ production, more CO intermediate produced by single-site Cu–MOF in situ for CF, and the enlarged active surface area by porous Cu–MOF. This work provides a strategy to combine MOFs with copper-based electrocatalysts to establish high-efficiency electrocatalytic CO₂RR.     

Atomic Interface Engineering of Single-Atom Pt/TiO2-Ti3C2 for Boosting Photocatalytic CO2 Reduction

Solar-driven CO₂ conversion into valuable fuels is a promising strategy to alleviate the energy and environmental issues. However, inefficient charge separation and transfer greatly limits the photocatalytic CO₂ reduction efficiency. Herein, single-atom Pt anchored on 3D hierarchical TiO₂-Ti₃C₂ with atomic-scale interface engineering is successfully synthesized through an in situ transformation and photoreduction method. The in situ growth of TiO₂ on Ti₃C₂ nanosheets can not only provide interfacial driving force for the charge transport, but also create an atomic-level charge transfer channel for directional electron migration. Moreover, the single-atom Pt anchored on TiO₂ or Ti₃C₂ can effectively capture the photogenerated electrons through the atomic interfacial Pt O bond with shortened charge migration distance, and simultaneously serve as active sites for CO₂ adsorption and activation. Benefiting from the synergistic effect of the atomic interface engineering of single-atom Pt and interfacial Ti O Ti, the optimized photocatalyst exhibits excellent CO₂-to-CO conversion activity of 20.5 µmol g⁻¹ h⁻¹ with a selectivity of 96%, which is five times that of commercial TiO₂ (P25). This work sheds new light on designing ideal atomic-scale interface and single-atom catalysts for efficient solar fuel conversation.     

Developing Water-Stable Pore-Partitioned Metal-Organic Frameworks with Multi-Level Symmetry for High-Performance Sorption Applications

A new perspective is proposed in the design of pore-space-partitioned MOFs that is focused on ligand symmetry properties sub-divided here into three hierarchical levels: 1) overall ligand, 2) ligand substructure such as backbone or core, and 3) the substituent groups. Different combinations of the above symmetry properties exist. Given the close correlation between nature of chemical moiety and its symmetry, such a unique perspective into ligand symmetry and sub-symmetry in MOF design translates into the influences on MOF properties. Five new MOFs have been prepared that exhibit excellent hydrothermal stability and high-performance adsorption properties with potential applications such as C₃H₆/C₂H₄ and C₂H₂/CO₂ selective adsorption. The combination of high stability with high benzene/cyclohexane selectivity of ≈13.7 is also of particular interest.     

Synthesis,structure and photocatalysis properties of two 3D Isostructural Ln (III)-MOFs based 2,6-Pyridinedicarboxylic acid

Two new 3D metal–organic frameworks (MOFs) named [Pr₂(PDA)₃·3H₂O]·H₂O (1) and [Nd₂(PDA)₃·3H₂O]·H₂O (2) [2,6-Pyridinedicarboxylic acid (H₂PDA)] were synthesized by solvothermal method. They were characterized by elemental analyses (EA), infrared spectroscopy (FT-IR), thermogravimetric analysis (TG), photocatalysis performance and single crystal X-ray diffraction studies (XRD). The XRD analysis indicated that MOFs (1) and (2) both belong to the monoclinic system with space group P2(1)/C. The structural model were drawn by the diamond software, and the structure revel that MOFs (1) and (2) adopt three-dimensional (3D) frameworks constructed by cross-linking of one-dimensional (1D) infinite chain secondary building unit (SBU) by 2,6-Pyridinedicarboxylic acid and hydrogen bond as linker. These frameworks feature channels inside which coordinated H₂O solvent molecules are located. Thermogravimetric analysis showed that both MOFs are thermally stable, the photocatalytic evaluation showed the materials have a good prospect in degration methylene blue. As for complex 1, the decomposition efficiency of Methylene blue was about 91.08% after 130?min and the complex 2 reach 90.45% after 160?min under the sun light.     

Photothermal‐Responsive Microporous Nanosheets Confined Ionic Liquid for Efficient CO2 Separation

2D materials hold promising potential for novel gas separation. However, a lack of in‐plane pores and the randomly stacked interplane channels of these membranes still hinder their separation performance. In this work, ferrocene based‐MOFs (Zr‐Fc MOF) nanosheets, which contain abundant of in‐plane micropores, are synthesized as porous supports to fabricate Zr‐Fc MOF supported ionic liquid membrane (Zr‐Fc‐SILM) for highly efficient CO₂ separation. The micropores of Zr‐Fc MOF nanosheets not only provide extra paths for CO₂ transportation, and thus increase its permeance up to 145.15 GPU, but also endow the Zr‐Fc‐SILM with high selectivity (216.9) of CO₂/N₂ through the nanoconfinement effect, which is almost ten times higher than common porous polymer SILM. Furthermore, based on the photothermal‐responsive properties of Zr‐Fc MOF, the performance is further enhanced (35%) by light irradiation through a photothermal heating process. This provides a brand new way to design light facilitating gas separation membranes.     

Confined Iron Fluoride@CMK‐3 Nanocomposite as an Ultrahigh Rate Capability Cathode for Li‐Ion Batteries

A facile and advanced architecture design of FeF₃·0.33H₂O impregnated CMK‐3 nanocomposite (FeF₃·0.33H₂O@CMK‐3) is presented. In the FeF₃·0.33H₂O@CMK‐3 nanocomposite, mesoporous carbon CMK‐3 can provide enough passageways for electron and Li⁺ transport to the confined nanosized FeF₃·0.33H₂O. The intimate conductive contact between the FeF₃·0.33H₂O nanoparticles and the carbon framework not only provides an expressway of electron transfer for Li⁺ insertion/extraction but also suppresses the growth and agglomeration of FeF₃·0.33H₂O during the crystallization process. As expected, the nanostructured materials exhibit impressive rate capability and excellent cyclicity. Remarkably, even under an ultrahigh charge/discharge rate of 50 C (the charge or discharge process takes a mere 72 s), the confined FeF₃·0.33H₂O@CMK‐3 still shows a high specific capacity of 78 mAh g^?1. By combining confined nanosized active material, high electron conductivity, and open framework, the FeF₃·0.33H₂O@CMK‐3 nanocomposite demonstrates excellent high‐rate capability and good cycling properties.     

Identification of thaumasite in concrete by Raman chemical imaging

Identification of thaumasite (CaSiO₃·CaO₃·CaSO₄·15H₂O) in concrete undergoing external sulfate attack by X-ray powder diffraction or by microscopic techniques is difficult due to its crystallographic and morphological similarity with ettringite. Widefield Raman chemical imaging via liquid crystal tunable filter (LCTF) technology has been used in a preliminary study to determine the presence of thaumasite in association with ettringite (3CaO·Al₂O₃·3CaSO₄·32H₂O) and gypsum (CaSO₄·2H₂O). Raman chemical imaging combines Raman spectroscopy with optical microscopy and digital imaging to provide images with molecular-based contrast. Thaumasite has three major peaks at 658, 990, 1076 cm⁻¹ and three minor peaks at 417, 453, 479 cm⁻¹. Ettringite has major peaks at 990, 1088 cm⁻¹. Gypsum has a major peak at 1009 cm⁻¹ and minor peaks at 417, 496, 621, 673, 1137 cm⁻¹. When these minerals are presented together, Raman chemical imaging provides an excellent way to determine their molecular composition and spatial distribution within the sample.