Imparting Stable and Ultrahigh Proton Conductivity to a Layered Rare Earth Hydroxide via Ion Exchange

Proton conductors are essential functional materials with a wide variety of potential applications in energy storage and conversion. In order to address the issues of low proton conductivity and poor stability in conventional proton conductors, a simple and valid ion-exchange method was proposed in this study for the introduction of stable and ultrahigh proton conductivity in layered rare earth hydroxides (LRHs). Test analyses by solid-state nuclear magnetic resonance, Fourier transform infrared spectroscopy, and powder X-ray diffraction revealed that the exchange of H2PO4- not only does not disrupt the layered structure of LRHs, but also creates more active proton sites and channels necessary for proton transport, thereby creating a high-performance proton conductor (LRH-H2PO4-). By utilizing this ion-exchange method, the proton conductivity of LRHs can be significantly enhanced from a low level to an ultrahigh level (>10-2 S·cm-1), while maintaining excellent long-term stability. Moreover, through methodically manipulating the guest ions and molecules housed within the interlayers of LRHs, a comprehensive explanation has been presented regarding the proficient mechanism of proton conduction in LRH-H2PO4-. As a result, this investigation presents a feasible and available approach for advancing proton conductor.

Synthesis, structure, and photocatalytic properties of a two-dimensional uranyl organic framework

A two-dimensional uranyl organic framework (UOF) UO2(L)(DMA) (1) (H2L = 2-aminoisophthalic acid, DMA = N, N-dimethylacetamide) has been solvothermally synthesized and characterized thoroughly by elemental analysis, infrared spectroscopy, single-crystal X-ray diffraction, solid fluorescence, powder X-ray diffraction, thermogravimetric analysis, and UV–visible spectroscopy. Furthermore, the degradation effciencies of UOF 1 to organic dye methylene blue (MB) and rhodamine B (RhB) are 93.2 and 86.5% under irradiation of visible light which indicates that UOF 1 has remarkable photocatalytic activity. UOF 1 also displayed a certain selectivity for mixed dyes of MB & RhB.

Progress in solid state and coordination chemistry of actinides in China

In the past decade, the area of solid state chemistry of actinides has witnessed a rapid development in China, based on the significantly increased proportion of the number of actinide containing crystal structures reported by Chinese researchers from only 2% in 2010 to 36% in 2021. In this review article, we comprehensively overview the synthesis, structure, and characterizations of representative actinide solid compounds including oxo-compounds, organometallic compounds, and endohedral metallofullerenes reported by Chinese researchers. In addition, Chinese researchers pioneered several potential applications of actinide solid compounds in terms of adsorption, separation, photoelectric materials, and photo-catalysis, which are also briefly discussed. It is our hope that this contribution not only calls for further development of this area in China, but also arouses new research directions and interests in actinide chemistry and material sciences.

Remarkable proton conducting behavior driven by synergistic effects in acid-base conjugated MOFs impregnated with sulphuric acid molecules

The Coulomb force between protons and negative charges usually leads to low proton diffusion and poor proton conductivity. Herein, acid-base conjugated MOFs of UiO-66-SO₃^--NH₃⁺ were constructed by linking sulfonic acid and amine groups to an organic skeleton. According to the XPS and elemental analysis, the ratio of 2-aminoterephthalic acid/2-sulfoterephthalic acid was ∼1.9 in UiO-66-SO₃^--NH₃⁺. After introducing sulphuric acid molecules, the MOF-based electrolyte exhibited a remarkable proton conductivity of 5.40 × 10^-1 S cm^-1 and low activation energy of 0.15 eV at 100% RH and 90 °C. This remarkable proton conducting behavior was generated by the synergistic system in the MOF, which contained certain synergistic effects such as between -SO₃^-⋯H⁺⋯SO₄^2- and NH₃⁺⋯SO₄^2-, therefore possessing a Grotthuss mechanism, which facilitates facile proton transport.

Crystalline Porphyrazine-Linked Fused Aromatic Networks with High Proton Conductivity

Fused aromatic networks (FANs) have been studied in efforts to overcome the low physicochemical stability of metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), while preserving crystallinity. Herein, we describe the synthesis of a highly stable and crystalline FAN (denoted as Pz-FAN) using pyrazine-based building blocks to form porphyrazine (Pz) linkages via an irreversible reaction. Unlike most COFs and FANs, which are synthesized from two different building blocks, the new Pz-FAN is formed using a single building block by self-cyclotetramerization. Controlled and optimized reaction conditions result in a highly crystalline Pz-FAN with physicochemical stability. The newly prepared Pz-FAN displayed a high magnitude (1.16×10^-2  S cm^-1 ) of proton conductivity compared to other reported FANs and polymers. Finally, the Pz-FAN-based membrane was evaluated for a proton-exchange membrane fuel cell (PEMFC), which showed maximum power and current densities of 192 mW cm^-2 and 481 mA cm^-2 , respectively.

Ionothermal synthesis of a highly crystalline zirconium phosphate proton conductor

A highly crystalline one-dimensional zirconium phosphate, (NH₄)₂[ZrF(PO₄)(HPO₄)] (ZrP-3), was facilely synthesized by the ionothermal method. The robust structure and rich hydrogen-bonded network make ZrP-3 an excellent proton conductor by having a proton conductivity higher than 10^-2 S cm^-1 at 90 °C and 95% RH. The remarkable stability makes ZrP-3 a promising solid electrolyte material for proton exchange membrane fuel cells.

Switched Proton Conduction in Metal-Organic Frameworks

Stimuli-responsive materials can respond to external effects, and proton transport is widespread and plays a key role in living systems, making stimuli-responsive proton transport in artificial materials of particular interest to researchers due to its desirable application prospects. On the basis of the rapid growth of proton-conducting porous metal-organic frameworks (MOFs), switched proton-conducting MOFs have also begun to attract attention. MOFs have advantages in crystallinity, porosity, functionalization, and structural designability, and they can facilitate the fabrication of novel switchable proton conductors and promote an understanding of the comprehensive mechanisms. In this Perspective, we highlight the current progress in the rational design and fabrication of stimuli-responsive proton-conducting MOFs and their applications. The dynamic structural change of proton transfer pathways and the role of trigger molecules are discussed to elucidate the stimuli-responsive mechanisms. Subsequently, we also discuss the challenges and propose new research opportunities for further development.

Advances and perspectives of actinide chemistry from ex situ high pressure and high temperature chemical studies

High pressure high temperature (HP/HT) studies of actinide compounds allow the chemistry and bonding of among the most exotic elements in the periodic table to be examined under the conditions often only found in the severest environments of nature. Peering into this realm of physical extremity, chemists have extracted detailed knowledge of the fundamental chemistry of actinide elements and how they contribute to bonding, structure formation and intricate properties in compounds under such conditions. The last decade has resulted in some of the most significant contributions to actinide chemical science and this holds true for ex situ chemical studies of actinides resulting from HP/HT conditions of over 1 GPa and elevated temperature. Often conducted in tandem with ab initio calculations, HP/HT studies of actinides have further helped guide and develop theoretical modelling approaches and uncovered associated difficulties. Accordingly, this perspective article is devoted to reviewing the latest advancements made in actinide HP/HT ex situ chemical studies over the last decade, the state-of-the-art, challenges and discussing potential future directions of the science. The discussion is given with emphasis on thorium and uranium compounds due to the prevalence of their investigation but also highlights some of the latest advancements in high pressure chemical studies of transuranium compounds. The perspective also describes technical aspects involved in HP/HT investigation of actinide compounds.

Developing a Unique Hydrogen-Bond Network in a Uranyl Coordination Framework for Fuel Cell Applications

Crystalline materials with persistent high anhydrous proton conductivity that can be directly used as a practical electrolyte of the intermediate-temperature proton exchange membrane fuel cells for durable power generation remain a substantial challenge. The present work proposes a unique way of the axial uranyl oxo atoms as hydrogen-bond acceptors to form a dense hydrogen-bonded network within a stable uranyl-based coordination polymer, UO₂(H₂PO₃)₂(C₃N₂H₄)₂ (HUP-3). It exhibits stable and efficient anhydrous proton conductivity over a super-wide temperature range (-40-170 °C). It was also assembled into a H₂/O₂ fuel cell as the electrolyte and shows a high electrical power density of 11.8 mW·cm^-2 at 170 °C, which is among one of the highest values reported from crystalline solid electrolytes. The cell was tested for over 12 h without notable power loss.

Superprotonic Conductivity of a Functionalized Metal-Organic Framework at Ambient Conditions

Seeking fast proton transport pathways at ambient conditions is desirable but challenging. Here, we report a strategy to synthesize a composite material with a polyoxometalate (POM) and an ionic liquid (IL) confined in stable metal-organic framework (MOF) channels through electrostatic interaction. The obtained SO₃H-IL-PMo₁₂@MIL-101 possesses fast proton transfer, and its proton conductivity can reach 1.33 × 10^-2 S cm^-1 at ambient conditions (30 °C, 70% relative humidity (RH)), which is the highest value among the MOF-based proton conductors operated in an ambient environment. Therefore, it has the potential of becoming a room-temperature proton conductor without a humidifier. Importantly, the composite material is further fabricated into a composite membrane for proton-exchange membrane fuel cells (PEMFCs), which can deliver a power density of 0.93 mW cm^-2 at 30 °C and 98% RH. This result can lay a fundamental basis for the application of MOF-based proton conductors in the area of electrochemical energy conversion.

Proton-conducting metal–organic frameworks with linkers containing anthracenyl and sulfonate groups

Co(dia)1.5(Hsip)(H2O)·H2O (1) and Zn2(μ-OH)(dia)2(sip)·2H2O (2) were prepared from the same set of ligand precursors. They exhibited bnn and dia topologies, respectively. Factors that contributed to the higher proton conductivity of 1 were presented.

Lanthanide-uranyl phosphonates constructed from diethyl ((phenylsulfonyl)methyl)phosphonate

Lanthanide-uranyl phosphonates possess intriguing crystal structures and huge application prospects, but the construction of these materials remains challenging. In this work, we demonstrate that new uranyl and lanthanide-uranyl sulfonylphosphonates with elegant crystal structures and photophysical properties can be assembled hydrothermally by employing the heterofunctional diethyl phosphonate (diethyl ((phenylsulfonyl)methyl)phosphonate, Et₂L) as a precursor ligand, which provides an effective strategy for the construction of lanthanide-uranyl phosphonates.

Single-crystal superprotonic conductivity in an interpenetrated hydrogen-bonded quadruplex framework

A proton-transporting pathway is crucial to the conduction mechanism in fuel cells and biological systems. Here, we report a novel 5-fold interpenetrated three-dimensional (3D) hydrogen-bonded quadruplex framework, which exhibits an ultrahigh single-crystal proton conductivity of 1.2(1) × 10^-2 S cm^-1 at 95 °C and 98% relative humidity, benefitting from the spiral H₃O⁺/H₂O chains in 1D pore channels studded with COOH/COO^- groups.

The Role of Acidity in the Synthesis of Novel Uranyl Selenate and Selenite Compounds and Their Structures

Herein, the novel uranyl selenate and selenite compounds Rb2[(UO2)2(SeO4)3], Rb2[(UO2)3(SeO3)2O2], Rb2[UO2(SeO4)2(H2O)]·2H2O, and (UO2)2(HSeO3)2(H2SeO3)2Se2O5 have been synthesized using either slow evaporation or hydrothermal methods under acidic conditions and their structures were refined using single crystal X-ray diffraction. Rb2[(UO2)2(SeO4)3] synthesized hydrothermally adopts a layered 2D tetragonal structure in space group P42/ncm with a = 9.8312(4) Å, c = 15.4924(9) Å, and V = 1497.38(15) Å, where it consists of UO7 polyhedra coordinated via SeO4 units to create units UO2(SeO4)58− moieties which interlink to create layers in which Rb+ cations reside in the interspace. Rb2[(UO2)3(SeO3)2O2] synthesized hydrothermally adopts a layered 2D triclinic structure in space group P1¯ with a = 7.0116(6) Å, b = 7.0646(6) Å, c = 8.1793(7) Å, α = 103.318(7)°, β = 105.968(7)°, γ = 100.642(7)° and V = 365.48(6) Å3, where it consists of edge sharing UO7, UO8 and SeO3 polyhedra that form [(UO2)3(SeO3)2O2] layers in which Rb+ cations are found in the interlayer space. Rb2[UO2(SeO4)2(H2O)]·2H2O synthesized hydrothermally adopts a chain 1D orthorhombic structure in space group Pmn21 with a = 13.041(3) Å, b = 8.579(2) Å, c = 11.583(2) Å, and V = 1295.9(5) Å3, consisting of UO7 polyhedra that corner share with one H2O and four SeO42− ligands, creating infinite chains. (UO2)2(HSeO3)2(H2SeO3)2Se2O5 synthesized under slow evaporation conditions adopts a 0D orthorhombic structure in space group Cmc21 with a = 28.4752(12) Å, b = 6.3410(3) Å, c = 10.8575(6) Å, and V = 1960.45(16) Å3, consisting of discrete rings of [(UO2)2(HSeO3)2(H2SeO3)2Se2O5]2. (UO2)2(HSeO3)2(H2SeO3)2Se2O5 is apparently only the second example of a uranyl diselenite compound to be reported. A combination of single crystal X-ray diffraction and bond valance sums calculations are used to characterise all samples obtained in this investigation. The structures uncovered in this investigation are discussed together with the broader family of uranyl selenates and selenites, particularly in the context of the role acidity plays during synthesis in coercing specific structure, functional group, and topology formations.

Integrated Photoresponsive Alkaline Earth Metal Coordination Networks: Synthesis, Topology, Photochromism and Photoluminescence Investigation

Photoresponsive materials are a key part of the age of smart technology that have potential in a broad range of applications. Coordination networks (CNs) are widely used due to their designability and stability. In this work, three novel alkaline earth metal coordination networks (AEM-CNs): [Mg(CMNDI)(H₂ O)₂ ], [Ca(CMNDI)(H₂ O)₂ ]⋅H₂ O, and [Sr(CMNDI)(H₂ O)(DMF)] with fsl, cds, and scn topology nets were synthetized via N,N'-bis(carboxymethyl)-1,4,5,8-naphthalenediimide (H₂ CMNDI); the scn net is not found in the Reticular Chemistry Structure Resource or ToposPro. The reusable and sensitive photochromic properties of the three CNs enable them to be used as secret inks or ultraviolet detectors. In addition, the CNs also exhibited reusable photoluminescent turn-off toward the drug molecules, balsalazide disodium (Bal.) and colchicine (Col.), with good limits of detection of 0.16 and 0.70 μM. To the best of our knowledge, this is the first study of a fluorescence sensor for Bal. Thus, the AEM-CNs provide a design idea for integrated photoresponsive materials that could be further improved in the near future by further study.

High Proton Conductivity in Nafion/Ni-MOF Composite Membranes Promoted by Ligand Exchange under Ambient Conditions

Metal-organic frameworks (MOFs) have appeared to be promising competitive candidates as crystalline porous materials for proton conduction. Explorations of the method of preparation of proton conductive MOFs and the proton transfer mechanism have enabled them to attract widespread attention, and tremendous efforts have been made to improve the proton conductivity of MOFs. On the basis of our previous work, we explicitly propose that ligand exchange can upgrade the proton conduction performance of MOFs. Using MOF-azo as the precursor, the proton conductivities of exchange products MOF-bpy and MOF-bpe increase by 3.5- and 2.8-fold, respectively. After the MOFs had been doped into the Nafion matrix to prepare composite membranes, the proton conduction performance of composite membranes filled with subproducts (2.6 × 10^-2 and 1.95 × 10^-2 S cm^-1) is significantly better than that of a composite membrane filled with a parent product (1.12 × 10^-2 S cm^-1) under ambient conditions (without heating or humidifying). The ligand exchange strategy presented herein demonstrates great promise for the development of high-proton conductivity MOFs and MOF composites with expanded future applications.

Conjugated Microporous Polymer with C≡C and C-F Bonds: Achieving Remarkable Stability and Super Anhydrous Proton Conductivity

Introducing nonvolatile liquid acids into porous solids is a promising solution to construct anhydrous proton-conducting electrolytes, but due to weak coordination or covalent bonds building these solids, they often suffer from structural instability in acidic environments. Herein, we report a series of steady conjugated microporous polymers (CMPs) linked by robust alkynyl bonds and functionalized with perfluoroalkyl groups and incorporate them with phosphoric acid. The resulting composite electrolyte exhibits high anhydrous proton conductivity at 30-120 °C (up to 4.39 × 10^-3 S cm^-1), and the activation energy is less than 0.4 eV. The excellent proton conductivity is attributed to the hydrophobic pores that provide nanospace for continuous proton transport, and the hydrogen bonding between phosphoric acid and perfluoroalkyl chains of CMPs promotes short-distance proton hopping from one side to the other.

Isonicotinic acid-templated metal phosphate–oxalates: solvent-free synthesis, luminescence, and proton conduction

Two new layered metal phosphate–oxalates were prepared under solvent-free conditions using isonicotinic acid as a structure-directing agent, which show interesting photoluminescence and proton-conducting properties.

Structural, optical, dielectric and electrical transport properties of a [Mg(H2O)6]2+-templated proton conducting, semiconducting and photoresponsive 3D hydrogen bonded supramolecular framework

{[Co(2,5-Pdc)2,(H2O)2]2−·[Mg(H2O)6]2+·4(H2O)} (where 2,5-pdc = 2,5-pyridinedicarboxylate): a proton conducting semiconducting photoresponsive [Mg(H2O)6]2+ templated 3D hydrogen bonded supramolecular framework (HSF).

A stable mixed-valent uranium(v,vi) organic framework as a fluorescence thermometer

A stable mixed-valent uranium(v/vi) organic framework with a 3D interpenetrating structure was synthesized, which can be used as a dual-responsive fluorescence temperature sensor based on the fluorescence intensity and fluorescence lifetime.

The first actinide polyiodate: a complex multifunctional compound with promising X-ray luminescence properties and proton conductivity

The synthesis of the first actinide polyiodate, K₄[(UO₂)₂(IO₃)₆(I₄O₁₁)]·(HIO₃)₄(H₂O)₆ (UP-1), is described and its X-ray luminescent and proton conductivity properties are examined.

Pillared-layered indium phosphites templated by amino acids: isoreticular structures, water stability, and fluorescence

Two crystalline open-framework indium phosphites (denoted SCU-31 and SCU-32) were prepared using amino acids as structure-directing agents. They have isoreticular pillared-layered structures built up from 6 × 1 and 4 = 1 clusters. Notably, the two compounds show excellent water stability and exhibit blue fluorescence under UV light irradiation at room temperature. The proton-conducting behaviour of SCU-31 was also investigated.

Variability of Uranyl Carboxylates from Rigid Terophenyldicarboxylic Acid Ligands

Three uranyl carboxylates, namely, (UO₂)(L¹)(H₂O)_0.5 (1), [(UO₂)(L²)(H₂O)]·2H₂O (2), and [(UO₂)(L²)(H₂O)]·(CH₃CN) (3), were synthesized hydrothermally from 2',3',5',6'-tetramethyl-(1,1':4',1″-terphenyl)-4,4″-dicarboxylic acid (H₂L¹) and 2',5'-dimethyl-(1,1':4',1″-terphenyl)-3,3″-dicarboxylic acid (H₂L²), which are all steric carboxylic acid ligands but vary with the carboxylic acid group position and methyl group number. It is found that compound 1 displays a three-dimensional 8-fold-interpenetrated net with channels running along the c direction. Compounds 2 and 3 are isostructural, and all display two-dimensional-layered crystal structures but contain different guest molecules. The photophysical measurements reveal that compounds 1 and 2, which contain disordered water molecules, are luminescence-quenched, whereas compound 3 containing acetonitrile molecules is luminescent.

Proton-Conductive Coordination Polymers Based on Diphenylsulfone-3,3'-disulfo-4,4'-dicarboxylate with Well-Defined Hydrogen Bonding Networks

The diphenylsulfone-3,3'-disulfo-4,4'-dicarboxylic acid (H₄-DPSDSDC) ligand and its coordination polymers, [K₂Zn(C₁₄H₆S₃O₁₂)(H₂O)₄]_n (1) and {[Cu₃(μ₃-OH)₂(C₁₄H₆S₃O₁₂)(H₂O)₃(DMF)]·3(H₂O)}_n (2) (C₁₄H₆S₃O₁₂ = diphenylsulfone-3,3'-disulfo-4,4'-dicarboxylate), were synthesized. The Zn(H₂O)₄ units in 1 are connected by DPSDSDC^4- ligands to generate a one-dimensional (1D) chain, which is bridged by K-O bonds associated with bridging water molecules and sulfonate groups to yield a two-dimensional (2D) layer. In 2, the 1D hydroxyl-bridging Cu(II) chains are connected by DPSDSDC^4- ligands to give a 2D layer. The 2D layers in 1 and 2 are further connected by interlayered hydrogen bonds to give three-dimensional (3D) frameworks. Compounds 1 and 2 have good conductivities of 1.57 × 10^-4 and 5.32 × 10^-5 S cm^-1, respectively. Continuous well-defined hydrogen bonding networks associated with water molecules, sulfonate groups, and carboxylate groups were observed in compounds 1 and 2. Such hydrogen bonding networks provide hydrophilic domains and effective transfer pathways for protons. Here, we present elegant examples of a precise determination of the pathways for proton transport.

Dual-Functional Proton-Conducting and pH-Sensing Polymer Membrane Benefiting from a Eu-MOF

Porous metal-organic frameworks (MOFs) have demonstrated a great potential in proton conduction and luminescence sensing due to functionalized nodes, ligands and channels, or pores. Herein, we prepared a hydrothermally stable Eu-MOF that also resisted acid and base using a bifunctional organic ligand containing carboxylic acid groups, which are easily coordinated to Eu ions, and Eu-phobic tetrazolyl groups as potential proton-hopping sites. The hydrogen bond network, which was constructed by the uncoordinated anionic tetrazolium and the coordinated and free water molecules, endowed this Eu-MOF with the highest proton conductivity of 4.45 × 10^-2 S/cm at 373 K and 93% relative humidity. The proton conductivity of the Nafion membrane containing this Eu-MOF increased 1.74 times. More interestingly, the hybrid membrane displayed luminescence pH sensing because the changeable protonation levels of uncoordinated tetrazolium groups along with the pH tuned the emission of embedded Eu-MOFs. Such a dual-functional MOF-based hybrid membrane including proton conduction and pH sensing is reported for the first time, which could open an avenue to the more practical application for functional MOFs.

Metal-Organic Frameworks as a Versatile Platform for Proton Conductors

Metal-organic frameworks (MOFs) are an intriguing type of crystalline porous materials that can be readily built from metal ions or clusters and organic linkers. Recently, MOF materials, featuring high surface areas, rich structural tunability, and functional pore surfaces, which can accommodate a variety of guest molecules as proton carriers and to systemically regulate the proton concentration and mobility within the available space, have attracted tremendous attention for their roles as solid electrolytes in fuel cells. Recent advances in MOFs as a versatile platform for proton conduction in the field of humidity condition proton-conduction, anhydrous atmosphere proton-conduction, single-crystal proton-conduction, and including MOF-based membranes for fuel cells, are summarized and highlighted. Furthermore, the challenges, future trends, and prospects of MOF materials for solid electrolytes are also discussed.

Noncomplexed Cucurbituril-Mediated Structural Evolution of Layered Uranyl Terephthalate Compounds

Template synthesis is one of the most feasible ways to explore new uranyl compounds with intriguing structures and properties. Here we demonstrate the preparation of six novel "sandwichlike" uranyl coordination polymers (UCPs) based on two-dimensional uranyl-terephthalate acid (H₂TP) networks using CBn (n = 5, 6, 8) as template ligands in the presence of different cations (Na⁺, K⁺, Cs⁺, or H₂N(CH₃)₂⁺). Compound 1 ([UO₂(TP)₂][Na₂(CB5)(H₂O)](H₂O)₅) is composed of layered uranyl-TP networks with the complex of CB5 and sodium cations as template ligands. In compound 2 ([(UO₂)₂(TP)₃]₂(CB6)(H₂O)₁₀), CB6 located between uranyl-TP networks contacts them by π-π interactions and hydrogen bonds. Compound 3 ([(UO₂)₂(TP)₃]₂[Na₂(H₂O)₁₀(CB6)]) is the same as compound 2 except for sodium cations bonding with CB6. Similarly in compound 4 ([(UO₂)₂(TP)₃][Cs(H₂O)₃(CB6)]), CB6 is a capsulelike structure capped with two cesium cations and interacts with uranyl-TP networks through π-π and C-H···π interactions. Compound 5 ([(UO₂)₂(TP)₃(HCOO)₂][K(H₂O)₂(CB5)]₂[H₂N(CH₃)₂]₂(CB6)(H₂O)₆) consists of both templates of CB6 and CB5 in which each CB5 is capped with one potassium cation while the H₂N(CH₃)₂⁺ cation is held at CB6 portals. In compound 6 ([(UO₂)₂(TP)₃]₂[UO₂(TP)₂(H₂O)₂][Cs(CB8)₃(H₂O)₄](H₂O)₁₆), CB8 ligands are connected by cesium cations to form a triangle motif and are further located between the uranyl-TP networks as template agents. All of the 2D layered structures with free CBn or cation-anchored CBn intercalate into the laminates of uranyl-terephthalate and shows a cucurbituril-mediated structural evolution. The regulating role of CBn as structure-directing template agents for the construction of layered UCPs through outer-surface interactions with layers of uranyl terephthalate is demonstrated, especially for the case of CB6 with contractive interlayer spacing.

Modulated synthesis and isoreticular expansion of Th-MOFs with record high pore volume and surface area for iodine adsorption

Isoreticular expansion of Th-MOFs via modulated synthesis yielded seven hierarchical complexes with superior quality single crystals, record high void space and BET surface area among Th materials, and exceptional iodine adsorption capacities.

The presence of mixed-valent silver in the uranyl phenylenediphosphonate framework

A 2-D silver uranyl phosphonate presents both Ag⁺ and Ag⁰ atoms in the free space between the adjacent layers and the incorporation of the mixed-valent silver sites results in the quenching of the fluorescent emission.

Structural features of proton-conducting metal organic and covalent organic frameworks

Proton conductivity in MOFs and COFs have been attracted due to their applicability as electrolytes in proton exchange membrane fuel cells. A short overview with recent updates on the structural features of MOFs and COFs for proton conduction are presented here.

Ultrahigh Proton Conduction in Two Highly Stable Ferrocenyl Carboxylate Frameworks

Nowadays, although research of proton conductive materials has been extended from traditional sulfonated polymers to novel crystalline solid materials such as MOFs, COFs, and HOFs, research on crystalline ferrocene-based carboxylate materials is very limited. Herein, we selected two hydrogen-bonded and π-π interactions-supported ferrocenyl carboxylate frameworks (FCFs), [FcCO(CH₂)₂COOH] (FCF 1) and [FcCOOH] (FCF 2) (Fc = (η⁵-C₅H₅)Fe(η⁵-C₅H₄)) to fully investigate their water-mediated proton conduction. Their excellent thermal, water, and chemical stabilities were confirmed by the means of thermogravimetric analyses, PXRD, and SEM determinations. The two FCFs indicate temperature- and humidity-dependent proton conductive features. Intriguingly, their ultrahigh proton conductivities are 1.17 × 10^-1 and 1.01 × 10^-2 S/cm, respectively, under 100 °C and 98% RH, which not only are comparable to the commercial Nafion membranes but also rank among the highest performing MOFs, HOFs, and COFs ever described. On the basis of the structural analysis, calculated E_a value, H₂O vapor adsorption, PXRD, and SEM measurements, reasonable conduction mechanisms are highlighted. Our research provides a novel inspiration for finding new high proton conducting crystalline solid materials. Importantly, the outstanding conducting performance of 1 and 2 suggests their, hopefully, potential in fuel cells and related electrochemical fields.

Cluster–oxalate frameworks with extra-large channels: solvent-free synthesis, chemical stability, and proton conduction

Two cluster–oxalate frameworks (denoted as SCU-62 and SCU-65) were prepared under solvent-free conditions.