Framework Materials Research Articles

Recent progress in magnetic covalent organic framework materials for the enrichment and detection of typical organic pollutants

Trace contaminants are toxic and their widespread presence in the environment potentially threatens human health. The levels of these pollutants are often difficult to determine directly using instruments owing to the complexities of environment matrices. Hence, pretreatment steps, such as sample purification and concentration, are key along with various processes that enhance the accuracy and sensitivity of the detection method. To date, researchers have successfully developed a variety of efficient and reliable sample-pretreatment techniques that are based on different principles. Among these, magnetic solid-phase extraction (MSPE) is a rapid and efficient sample-pretreatment technology that is based on the similar solid-phase-extraction (SPE) principle, which mainly enriches target analytes by exploiting their interactions with functional groups on the surfaces of magnetic materials, thereby achieving rapid separation when an external magnetic field is applied. MSPE has been a focus of attention in the environmental-sample-pretreatment, food-analysis, and other fields owing to advantages that include ease of operation, low cost, and high enrichment efficiency. The selection of the magnetic material is key to MSPE process because traditional magnetic materials exhibit certain functionality limitations. Accordingly, designing and synthesizing green and efficient functionalized magnetic materials have become a research focus in this field, with researchers having extensively explored multiple ways of preparing functionalized modified magnetic materials through the introduction of a variety of emerging materials, including metal-organic frameworks (MOFs), covalent organic frameworks (COFs), carbon nanotubes (CNTs), graphene oxide (GO), and other specific functional groups to modify magnetic materials and effectively expanded the applications scope of MSPE. Among these, COFs are porous crystalline materials consisting of light elements (C, N, H, O and B, etc.) linked through covalent bonds. COFs are mainly classified as imine COFs, boronic-acid COFs, triazine COFs, and ketenimine COFs according to bonding type. Moreover, it is worth mentioning that COFs can be synthesized from a number of monomers, and the functional groups exposed on the COF surface can also be used for further modification purposes. COFs are versatile and modifiable; consequently, they have attracted significant research attention, with a series of COF-functionalized magnetic materials having been designed and synthesized. The magnetic COFs (MCOFs) combine the advantages of COFs and magnetic materials. MCOFs are not only endowed with the large specific surface areas, high porosities, and good stabilities that are characteristic of COFs, but also exhibit the rapid separation and reusability characteristics of magnetic material, thereby quickly and efficiently enriching targets through hydrogen bonding, hydrophobicity, π-π stacking, and van der Waals forces, making them ideal sample-pretreatment materials. MCOFs have also been converted into more-versatile functional materials using post-modification strategies. Combining MCOFs with advanced analytical techniques, such as high performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS) has effectively improved the limits of detection (LODs) for various analytes as well as method accuracy; these techniques have been widely used to enrich and detect trace pollutants. However, some material design and synthesis challenges remain and need to be overcome, despite the promising potential of MCOFs. Future research needs to focus on exploring novel synthetic strategies that reduce experimental costs and improve the functionalities of MCOFs while expanding their applicabilities to broader sample matrices. In this review, we first introduce and discuss the construction and functionalized designs of various MCOF composites, and then summarize their use in applications that include the enrichment and detection of pesticides, endocrine disruptors (EDCs), pharmaceuticals, and personal care products (PPCPs), and finally provide an outlook on future developmental prospects.

Research advance of solid-phase microextraction based on covalent organic framework materials

Solid-phase microextraction (SPME) is a fast and simple sample preparation technique that enables the enrichment of analytes, and it is used in combination with other detection techniques to provide accurate and sensitive analytical methods. SPME is widely used in environmental monitoring, food safety, life analysis, biomedicine, and other applications. The extractive coating is the core of the SPME technique, and the properties of the extractive coating greatly influence extraction selectivity and efficiency, as well as the enrichment effect. Therefore, the development of new and efficient extractive coating materials remains a hot topic in the analytical chemistry and sample preparation fields. Covalent organic frameworks (COFs) are a kind of porous crystalline network polymer materials formed by covalent bonds. Owing to the advantages of large specific surface area, high porosity, good stability, high designability, simple synthesis and post-modification, etc., it has been widely used in gas adsorption, catalysis, sensing and drug delivery. In recent years, COFs have attracted much attention in the field of sample preparation. A variety of novel COF-based SPME materials had been developed for extracting and enriching various types of analytes through π-π interaction, hydrophilic/hydrophobic interaction, electrostatic adsorption, and hydrogen-bonding, as well as pore effects. In this paper, the research advances of COFs for using in fiber-, in tube-, and membrane-based SPME over the past three years were discussed. Fiber surfaces had been modified with functionalized COFs or COF-hybrid materials for use in SPME through physical coating, in-situ growth, and chemical-bonding approaches. The combination of SPME fiber and chromatographic analysis can be used to detect a variety of analytes such as polycyclic aromatic hydrocarbons, phthalates, polychlorinated biphenyls, and pesticides in environmental and food samples, with good enrichment effects, wide linear ranges, and high sensitivity. Based on in tube-SPME, COFs-based monolithic column and fiber-filled tube as the extraction tubes were combined with high performance liquid chromatography online to develop highly sensitive detection methods for synthetic phenolic antioxidants and bisphenol compounds, respectively. In addition, COFs had also been used in membrane SPME technique, showing high efficiency in the extraction of trace polychlorinated biphenyls in environmental water. Finally, the development trends of COFs in the field of SPME was prospected.

Human serum albumin microspheres synchronously loaded with ZIF-8 and triptolide (TP) for the treatment of intrahepatic cholangiocarcinoma.

Intrahepatic cholangiocarcinoma (ICC) is the second most common primary liver tumor and remains a fatal malignancy in most patients. Only 20% to 30% of patients can be treated with potentially curative surgical resection. Local therapies such as radioembolization and hepatic arterial perfusion may be a more effective treatment strategy. The active ingredients of natural plants have aroused wide interest in the treatment of tumors. Triptolide shows toxic effects on a variety of epithelioid carcinoma cells. However, there is currently a lack of suitable delivery system for the treatment of ICC. In this study, organometallic framework material ZIF-8 was chosen to load TP, and then encapsuled in HSA micro-nanoparticles for the perfusion treatment of ICC. The results of SEM, XRD, and FTIR showed that ZIF-8 nanoparticles were encapsuled in HSA micro-nanoparticles. ZIF-8 nanoparticles (57.89 ± 12.24%) and TP@ZIF-8/HSA (36.8 ± 4.71%) micro-nanoparticles could significantly inhibited proliferation of RBE cell. Also, TP@ZIF-8/HSA micro-nanoparticles of all groups exhibited favorable cytocompatibility to L929 cells and hemocompatibility. RT-qPCR and western blot showed that ZIF-8 and TP induced apoptosis in cancer cells through mitochondria-related pathways. The results demonstrated that TP@ZIF-8/HSA was a potential chemotherapy candidate for the treatment of ICC.

Fabrication of Dual-Ligand Zn-MOFs with Asynchronous Fluorescence Response for Efficient Ratiometric/Visual Sensing of Tetracycline Antibiotics in Animal-Derived Foods.

The extensive use of tetracyclines in livestock poses health risks due to their residues in animal-derived food; therefore, developing simple detection methods to replace complex traditional approaches is of paramount importance. Here, we developed a dual-ligand zinc-based metal-organic framework material, Zn-BTC-BDC-NH2 (denoted as ZTD), for the detection of tetracyclines. The intrinsic blue fluorescence of ZTD was quenched upon the introduction of tetracyclines due to electron transfer from -NH2 of ZTD to -CO- and -OH groups of tetracycline molecules; meanwhile, the new green fluorescence emission was generated through π-π stacking between aromatic rings and the formation of complexes between Zn2+ and C-O/C═O groups. In real food samples, ZTD exhibited recovery rates ranging from 93.62 to 110.66%, with detection limits as low as 0.011 μmol·L-1. Additionally, a ZTD fluorescence test paper was developed for portable detection. This study presents a novel tetracycline detection method, offering insights into multiligand metal-organic framework preparation and future sensing method design.

Electron Microscopy Reveals Inhomogeneous Adsorption of Iodine and Concurrent Defect Formation in a Metal-Organic Framework.

Adsorption behaviors are typically examined through adsorption isotherms, which measure the average adsorption amount as a function of partial pressure or time. However, this method is incapable of identifying inhomogeneities across the adsorbent, which may occur in the presence of strong intermolecular interactions of the adsorbate. In this study, we visualize the adsorption of molecular iodine (I2) in the metal-organic framework material MFM-300(Sc) using high-resolution scanning transmission electron microscopy (STEM). Our observations demonstrate that, counterintuitively, I2 adsorption in MFM-300(Sc) occurs in an inhomogeneous manner, regardless of the I2 uptake level. Even at adsorption saturation, corresponding to an average of 23 iodine atoms per unit cell, MOF channels with significantly varying iodine contents─from nearly empty to densely filled─coexist. Image simulations suggest that the most densely packed I2 may locally form the previously proposed triple-helix structure, corresponding to up to 142 iodine atoms per unit cell. Furthermore, STEM imaging reveals that I2 adsorption can induce the formation of structural defects, such as edge dislocations and stacking faults, within the MOF framework. These defects persist even after the complete removal of I2 molecules. Additionally, we have developed a surfactant-capping strategy to minimize the release of adsorbed I2 from MFM-300(Sc) and validated its effectiveness using STEM imaging.

Catalytic synthesis of vitamin E acetate using metal organic framework material ZIF-8

Vitamin E is an important fat soluble antioxidant, its acetate is the main derivative product of vitamin E. Using metal organic framework material ZIF-8 as a catalyst, vitamin E acetate (VEA) was prepared by catalyzing the esterification reaction of D-α-tocopherol and acetic anhydride in a solvent-free system. Firstly, the preparation conditions of metal organic framework materials were studied: different imidazole ligands, different zinc ion ligands, molar concentration ratio of Zn2+ to 2-methylimidazole(2-mIM), and preparation time. The results showed that the catalytic performance of ZIF-8 was optimal when Zn(CH3COO)2·2H2O was used as the zinc source, 2-mIM was used as the imidazole ligand, the molar concentration ratio of Zn2+ / 2-mIM was 1:20, and the preparation time was 1 hour. The yield of vitamin E acetate was 86.85%. The synthesis process of VEA was optimized by single factor experiments such as substrate molar ratio, reaction time, dosage of nano enzyme, reaction temperature and so on. The results showed that the yield of vitamin E acetate reached 96.31% under the optimal conditions of n (D-α-tocopherol) =1mmol, [n (D-α-tocopherol) : n (Acetic anhydride)] =1:15, reaction time 24 h, ZIF-8 dosage 0.05 g, reaction temperature 50 °C.

Crystalline Covalent Triazine Frameworks and 2D Triazine Polymers: Synthesis and Applications.

ConspectusCovalent triazine frameworks (CTFs) are a novel class of nitrogen-rich conjugated porous organic materials constructed by robust and functional triazine linkages, which possess unique structures and excellent physicochemical properties. They have demonstrated broad application prospects in gas/molecular adsorption and separation, catalysis, energy conversion and storage, etc. In particular, crystalline CTFs with well-defined periodic molecular network structures and regular pore channels can maximize the utilization of the features of CTFs and promote a deep understanding of the structure-property relationship. However, due to the poor reversibility of the basic reaction for constructing the triazine unit and the traditional harsh synthesis conditions, it remains a considerable challenge to synthesize crystalline CTFs with diverse molecular structures, and there is still a significant lack of understanding of their polymerization mechanism, which limits their precise structural design, large-scale preparation, and practical applications. As the basic building block of bulk crystalline CTFs, two-dimensional triazine polymers (2D-TPs) which ideally have single-atom thickness have also aroused intensive interest due to their ultrathin 2D sheet morphology with structural flexibility, a fully exposed molecular plane and active sites, and excellent dispersibility and processability. However, the efficient and scalable production of high-quality 2D-TPs and the investigation of their unique properties and functions remain largely unexplored.In this Account, we summarize our recent contributions to the synthesis and application exploration of crystalline CTFs and 2D-TPs. We first introduce the design, synthesis, and polymerization mechanism of the crystalline CTFs. In order to synthesize high-quality CTFs, we have successively used a series of new synthetic methods including a solution polymerization strategy, microwave-assisted superacid-catalyzed polymerization strategy, polyphosphoric acid-catalyzed polymerization strategy, and solvent-free FeCl3-catalyzed polymerization strategy, achieving the production of highly crystalline layered CTFs from the gram level to the hundred-gram level and then to the kilogram level and realizing new CTF molecular structures. We also reveal a direct ordered 2D polymerization mechanism that provided meaningful guidance for the controllable preparation of functional CTFs. Next, we introduce the design, synthesis, and formation mechanism of 2D-TPs. We have developed effective bottom-up and top-down strategies to prepare 2D-TPs for different needs. On one hand, we have established the dynamic interface polymerization method, the monomer-dependent method, and the solvent-free salt-catalyzed polymerization strategy for the direct synthesis of ultrathin 2D-TPs with thickness down to the single-layer limit and provided important insights into the 2D polymerization mechanism. On the other hand, we have opened up the physical and chemical exfoliation of crystalline layered CTFs such as liquid sonication and ball milling exfoliation and covalent and noncovalent modification exfoliation for the large-scale production of 2D-TPs. Then, we present the application progress of crystalline CTFs and 2D-TPs in various batteries, photo/electrocatalysis, and adsorbents with an emphasis on their unique and outstanding performance and structure-property relationship. Lastly, the main challenges faced by crystalline CTFs and 2D-TPs in practical applications and future research directions are discussed in detail. We hope that this Account will provide valuable insights and practical strategies for promoting the development of functional organic framework materials and 2D polymer materials.

Advancements in porous framework materials for chemiresistive hydrogen sensing: exploring MOFs and COFs.

Hydrogen is a zero-emissive fuel and has immense potential to replace carbon-emitting fuels in the future. The development of efficient H2 sensors is essential for preventing hazardous situations and facilitating the widespread usage of hydrogen. Chemiresistors are popular gas sensors owing to their attractive properties such as fast response, miniaturization, simple integration with electronics and low cost. Traditionally, semiconducting metal oxides (SMOs) and Pd-based materials have been widely investigated for chemiresistive H2 sensing applications. However, issues such as limited selectivity and poor reliability still hinder their use in real-time applications. Recent advancements have explored metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), offering new perspectives and potential applications in this field. MOFs and COFs belong to the crystalline framework (CF) family of materials and are highly porous, designable materials with tunable pore surfaces featuring sites for H2 interactions. They exhibit good selectivity towards H2 with quick response/recovery times at relatively low temperatures compared to SMOs. Furthermore, they provide an additional advantage of sensing H2 in the absence of oxygen, even at high concentrations of H2. In this perspective article, we summarize recent advancements and challenges in the development of H2 sensors employing MOFs, COFs, and their hybrid composites as sensing elements. Additionally, we discuss our perspective on hybridizing MOFs/COFs with SMOs and other nanomaterials for the future development of advanced H2 sensors.

Recent advances in designable nanomaterial-based electrochemical sensors for environmental heavy-metal detection.

The detection of heavy metals serves as a defence measure to safeguard the well-being of the human body and the ecological environment. Electrochemical sensors (ECS) offer significant benefits such as exceptional sensitivity, excellent selectivity, affordability, and portability. This review begins by elucidating the ECS principles and delves into recent advancements in the field of heavy metal detection, including the use of metal nanoparticles, carbon-based nanomaterials, and organic framework materials. Advanced materials enhance the sensitivity and selectivity of ECS, allowing it to efficiently and rapidly identify metallic contaminants in food and the environment. Finally, the future development of ECS and challenges encountered in the development process are discussed, and testing materials for the detection of heavy-metal ions for human health and environmental safety are comprehensively considered. This study is likely to attract the interest of environmentalists and those who prioritise human health.

A Tribo/Piezoelectric Nanogenerator Based on Bio-MOFs for Energy Harvesting and Antibacterial Wearable Device.

New types of metal-organic framework (MOF) materials have great potential in solving the current global dilemma on energy, environment, and medical care. Herein, based on two kinds of biomolecule-MOFs (Bio-MOFs) with favorable biocompatibility and degradation-reconstruction characteristics, we have established a self-powered muti-functional device to achieve an efficient and broad-spectrum environmental energy collection and biomedical applications. Combining Zn(II) and carnosine-based Zn-Car_MOF possessing a high piezoelectric response (d33 = 11.17 pm V-1) with patterned polydimethylsiloxane (PDMS) film, a tribo-piezoelectric hybrid nanogenerator (TPHG) is constructed with a synergy output of triboelectric and piezoelectric effects. The Zn-Car_TPHG demonstrates a high output performance (131V at 100kPa) and a wide range of pressure response (1Pa-100kPa), possessing applications in environmental energy collection and biomedical sensors. To expand the application of the wearable device, a conductive hexagonal prism MOF (Cu3(2,3,6,7,10,11-hexahydroxytriphenylene)2 (Cu-HHTP)) is synthesized and employed to load thymol (Thy). Cooperating with Zn-Car_TPHG, the resulting Cu-HHTP/Thy can achieve an efficient self-powered ROS (singlet oxygen (1O2) and hydroxyl radical (·OH)) generation and drug synergistic broad-spectrum sterilization effect (efficiency ≥ 98%). In a word, the flexible wearable device based on the muti-functional Bio-MOFs is sustainable and environmentally friendly, possessing wide application potential in fields of environmental energy collection, biosensors, and self-powered antibacterial.

Noble-metal-free Electrocatalysts for Selective Hydrogen Peroxide Generation via Oxygen Reduction Reaction.

Hydrogen peroxide (H2O2) is a versatile chemical widely used in various industries. The traditional anthraquinone method for H2O2 synthesis has environmental and safety concerns due to the use of organic solvents and hazardous by-products. The direct synthesis of H2O2 from H2 and O2 poses risks of flammability and explosion. Recently, the 2-electron oxygen reduction reaction (2e- ORR) method has emerged as a promising alternative, offering safety, environmental friendliness, and cost-effectiveness. This method utilizes gas diffusion electrodes to efficiently generate H2O2 without the need for additional dilution. In this review, we focus on the recent advancements in noble-metal-free materials for 2e- ORR electrocatalysis, which play a crucial role in the efficient production of H2O2. These materials, including transition metal compounds, macrocyclic complexes, carbon-based catalysts, framework materials, and MXene catalyst, demonstrate significant advantages in enhancing H2O2 yield. The development of these non-precious metal catalysts can reduce costs and improve sustainability and promote the commercialization of related technologies. The review concludes with an outlook on the future trends of 2e- ORR electrocatalysts.

Biomechanical behavior of titanium, cobalt-chromium, zirconia, and PEEK frameworks in implant-supported prostheses: a dynamic finite element analysis

BackgroundThe mechanical properties of framework materials significantly influence stress distribution and the long-term success of implant-supported prostheses. Although titanium, cobalt-chromium, zirconia, and polyether ether ketone (PEEK) are widely used, their biomechanical performance under dynamic loading conditions remains insufficiently investigated. This study aimed to evaluate the biomechanical behavior of four framework materials with different Young's modulus using dynamic finite element stress analysis.MethodsA 3D edentulous maxillary model was extracted from a computer tomography (CT) database. Bone level implants with conical connection designs were placed in the anterior (canine) and posterior (first molar) areas. Anterior implants were parallel, yet posterior implants were inclined distally by 30 degrees. According to the framework material, four groups were formed: cobalt-chromium (Co-Cr), zirconia (Zr), titanium (Ti), and polyether ether ketone (PEEK). For each framework material, twelve separate models of analysis were created by applying force in three different orientations. Dynamic forces were employed to replicate the chewing process. Principal and von Mises stresses were measured and evaluated.ResultsThe PEEK framework exhibited the highest maximum von Mises stress values (372.55 MPa) on the abutment and the highest maximum principle stress values (59.27 MPa) in the cortical bone. The Co-Cr framework had the lowest minimum principle stress (3.98 MPa) in the trabecular bone. The displacements of the Co-Cr, Zr, Ti, and PEEK frameworks were 0.15 mm, 0.15 mm, 0.17 mm, and 0.35 mm, respectively.ConclusionFrameworks having a greater Young's modulus are less susceptible to deformation.

A fluorescent sensor based on pentafluoropropanoic acid-functionalized UiO-66-NH2 for enhanced selectivity and sensitivity of dicloran detection.

Apentafluoropropionic acid-functionalized fluorescent metal-organic framework material (UiO-66-NH2-PFPA) is prepared by a simple post-synthetic modification (PSM) strategy for the sensitive and selective detection of dichloran (DCN). The results of fluorescence experiments demonstrate that the sensitivity of UiO-66-NH2-PFPA (limit of detection, LOD = 0.478μM) to DCN is nearly 10.93 times higher than that of UiO-66-NH2 (LOD = 5.225μM)and the material hasgood selectivity and anti-interference ability. After the addition of DCN, the blue fluorescence of UiO-66-NH2-PFPA is obviously quenched. Therefore, the possible quenching mechanism is further discussed in combination with relevant experiments and density functional theory calculations. Moreover, the sensor is applied to the detection of DCN in fruit samples with a satisfactory recovery of 101.1-107.9%, which implies that UiO-66-NH2-PFPA is expected to be a candidate material for the detection of DCN in food.

Ultramicroporous Tröger's Base Framework Membranes With Ionized Sub-nanochannels for Efficient Acid/Alkali Recovery.

Membrane technology holds significant potential for the recovery of acids and alkalis from industrial wastewater systems, with ion exchange membranes (IEMs) playing a crucial role in these applications. However, conventional IEMs are limited to separating only monovalent cations or anions, presenting a significant challenge in achieving concomitant H⁺/OH⁻ permselectivity for simultaneous acid and alkali recovery. To address this issue, the charged microporous polymer framework membranes are developed, featuring rigid Tröger's Base network chains constructed through a facile sol-gel process. The intrinsic ultramicropore confinement and quaternary ammonium-charged functional groups provide ultrahigh size-sieving capability and enhanced Donnan exclusion for H⁺/OH⁻ selectivity; meanwhile, the internal protoplasmic channels of the polymer frameworks serve as highways for rapid ion transfer. The resulting membrane achieves high H⁺/Fe2⁺ and OH⁻/WO₄2⁻ selectivities of 694.4 and 181.0, respectively, for concurrent acid and alkali separation in diffusion dialysis and electrodialysis processes over extended operational periods (exceeding 1600 and 600 h, respectively), while maintaining remarkable transport rates. These results outperform most literature-reported and nearly all commercially available membranes. This study validates the novel applicability of polymer framework materials with ionized angstrom-scale channels and versatile functionalities in high-performance IEMs for acid/alkali resource recovery.

Employing Triphenylene-Based, Layered, Conductive Metal-Organic Framework Materials as Electrochemical Sensors for Nitric Oxide in Aqueous Media.

This paper describes the first use of conductive metal-organic frameworks as the active material in the electrochemical detection of nitric oxide in aqueous solution. Four hexahydroxytriphenylene (HHTP)-based MOFs linked with first-row transition metal nodes (M = Co, Ni, Cu, Zn) were compared as thin-film working electrodes for promoting oxidation of NO using voltammetric and amperometric techniques. Cu- and Ni-linked MOF analogs provided signal enhancement of 5- to 7-fold over a control glassy carbon electrode (SANO = 6.7 ± 1.2 and 5.7 ± 1.1 for Ni3(HHTP)2 and Cu3(HHTP)2, respectively) for detecting micromolar concentrations of NO. Zinc-based MOF electrodes offered more limited enhancement (SANO = 3.1 ± 0.5), while the cobalt-based MOF analog had intrinsic redox activity at potentials close to NO oxidation, which interfered with sensing. Combining MOFs with a conductive polymer improved electrode stability under repeated electrochemical scanning (14 ± 3% decrease in signal over 10 scans). The stabilized Ni3(HHTP)2@polymer-coated electrodes were able to detect NO at physiologically relevant concentrations (LOD = 9.0 ± 4.8 nM) in amperometric sensing experiments, and exhibited moderate selectivity against ascorbic acid and nitrite (log kj,NO = -1.3 ± 0.3 and -0.83 ± 0.68 for ascorbic acid and nitrite, respectively). This study demonstrates that layered, conductive 2D MOFs have promising applicability for NO detection in aqueous environments.

Protein-Guided Biomimetic Calcification Constructing 3D Nitrogen-Rich Core-Shell Structures Realizing High-Performance Lithium-Sulfur Batteries.

Biomimetic calcification is a micro-crystallization process that mimics the natural biomineralization process, where biomacromolecules regulate the formation of inorganic minerals. In this study, it is presented that a protein-assisted biomimetic calcification method for the in situ synthesis of nitrogen-doped metal-organic framework (MOF) materials. A series of unique core-shell structures are created by utilizing proteins as templates and guiding agents in the nucleation step, creating ideal conditions for shell growth. To further understand the influence of the protein and organic ligand on the morphology of the MOF shell, the competing mechanism toward metal ions is supposed. Through systematic experiments and analyses, a strategy to construct unique precursor structures by controlling calcification nucleation is proposed. After carbonization, protein-containing precursors exhibit exceptional porous characteristics, stability, and high nitrogen content. These attributes make them promising materials as sulfur hosts in lithium-sulfur batteries (LSB). Electrochemical tests confirm that biomimetic calcification-assisted 3D carbonaceous structure can effectively immobilize dissolved polysulfides, demonstrating strong adsorption and catalytic capabilities. This discovery not only opens up new avenues for employing biomimetic calcification as a sustainable method for batteries but also enlightens the fields of materials science, catalytic chemistry, and energy storage.

Surface Engineering of 2D Metal-Porphyrin Metal-Organic Frameworks Z-Scheme Heterostructure for Boosting and Stable Photocatalytic Hydrogen Evolution.

How to improve the stability and activity of metal-organic frameworks is an attractive but challenging task in energy conversion and pollutant degradation of metal-organic framework materials. In this paper, a facile method is developed by fabricating titanium dioxide nanoparticles (TiO2 NPs) layer on 2D copper tetracarboxylphenyl-metalloporphyrin metal-organic frameworks with zinc ions as the linkers (ZnTCuMT-X, "Zn" represented zinc ions as the linkers, the first "T" represented tetracarboxylphenyl-metalloporphyrin (TCPP), "Cu" represented the Cu2+ coordinated into the porphyrin macrocycle, "M" represented metal-organic frameworks, the second "T" represented TiO2 NPs layer, and "X" represented the added volume of n-tetrabutyl titanate (X = 100, 200, 300 or 400)). It is found that the optimized ZnTCuMT-200 showed greatly and stably enhanced H2 generation, which is ≈28.2 times and 47.0 times as high as those of the original ZnTCuM and TiO2, respectively. Combined with the results of free radical capture, X-ray photoelectron spectra (XPS), electron spin resonance (ESR), and theoretical calculation, a direct Z-scheme electron transfer mechanism is achieved to fully explain the enhanced photocatalytic performance. It demonstrates that facilely designing Z-scheme heterostructures based on porphyrin MOFs modified with an inorganic semiconductor layer can be an advantageous strategy for enhancing the stability and activity of photocatalytic hydrogen evolution.

Sub-5 Ångstrom Porosity Tuning in Calixarene-Derived Porous Liquids via Supramolecular Complexation Construction.

Precise sub-Ångstrom-level porosity engineering, which is appealing in gas separations, has been demonstrated in solid carbon, polymer, and framework materials but rarely achieved in the liquid phase. In this work, a gas molecular sieving effect in the liquid phase at sub-5 Ångstrom scale is created via sophisticated porosity tuning in calixarene-derived porous liquids (PLs). Type II PLs are constructed via supramolecular complexation between the sodium salts of calixarene derivatives and crown ether solvents. The chemical structure variation and assembly behavior of the porous host upon PL construction are monitored by spectroscopy-, X-ray-, and neutron-scattering techniques. The presence of permanent porosity in calixarene-derived PLs is verified by pressure swing gas uptake, altered CO2 physisorption behavior, and dynamic theoretical simulation. Sub-5 Ångstrom porosity tuning within the PL phase is achieved by introducing bulky substituted groups on the benzene ring of the calixarene host, which then greatly affects the dynamic motion and transport behavior of CO2 molecules and the Xe uptake performance. The approach being demonstrated in this work represents a promising pathway to tune and leverage the porosity effect for enhanced gas uptake capacity and selectivity in liquid sorbents.

Small-angle rigid-unit modes requiring linear strain compensation.

Group-theoretical and linear-algebraic methods and tools have recently been developed that aim to exhaustively identify the small-angle rotational rigid-unit modes (RUMs) of a given framework material. But in their current form, they fail to detect RUMs that require a compensating lattice strain which grows linearly with the amplitude of the rigid-unit rotations. Here, we present a systematic approach to including linear strain compensation within the linear-algebraic RUM-search method, so that any geometrically possible small-angle RUM can be detected.

Managing negative linear compressibility and thermal expansion through steric hindrance: a case study of 1,2-bis(4'-pyridyl)ethane cocrystals.

Multicomponent crystals have great scientific potential because of their amenability to crystal engineering in terms of composition and structure, and hence their properties can be easily modified. More and more research areas are employing the design of multicomponent materials to improve the known or induce novel physicochemical properties of crystals, and recently they have been explored as materials with abnormal pressure behaviour. The cocrystal of 1,2-bis(4'-pyridyl)ethane and fumaric acid (ETYFUM) exhibits a negative linear compressibility behaviour comparable to that of framework and metal-containing materials, but overcomes many of their deficiencies restricting their use. Herein ETYFUM was investigated at low temperature to reveal negative thermal expansion behaviour. Additionally, a cocrystal isostructural with ETYFUM, based on 1,2-bis(4'-pyridyl)ethane and succinic acid (ETYSUC), was exposed to high pressure and low temperature, showing that its behaviour is similar in nature to that of ETYFUM, but significantly differs in the magnitude of both effects. It was revealed that the minor structural difference between the acid molecules does not significantly affect the packing under ambient conditions, but has far-reaching consequences when it comes to the deformation of the structure when exposed to external stimuli.