Uranyl Clusters Based on 1,10-Phenanthroline Derivative Ligands: Synthesis, Crystal Structures, and Iodine Capture

The clusters have garnered widespread interest owing to their captivating structures and their potential applications in diverse scientific disciplines. Within this study, we synthesized two uranyl clusters, (UO2)3(DMF)2(CO3)(bmpd)·DMF (IHEP-34) and (UO2)10(O)2(OH)2(CO3)2(btpd)2 (IHEP-35), by the utilization of 1,10-phenanthroline derivative ligands in conjunction with uranyl cations through solvothermal synthesis techniques. Both clusters are characterized by a V-shaped [(UO2)3(CO3)]4+ unit, whose configuration strikingly differs from the typical triangular [(UO2)3(O)]4+/[(UO2)3(OH)]5+ structures. Density functional theory calculations show that the [U3] cluster and [U10] cluster boast of remarkable stability with the HOMO-LUMO gap of 2.13 and 0.90 eV, respectively. The [U10] clusters in IHEP-35 are orderly assembled through weak intermolecular interactions, forming a 3D supramolecular porous structure, which exhibits an excellent performance in the adsorption of gaseous iodine. The maximum adsorption capacity of IHEP-35 for gaseous iodine is 1324 mg·g-1. The analysis of XPS and Raman spectra reveals that the adsorbed iodine in IHEP-35 predominantly exists in the form of a triiodide anion.

Three-dimensional van der Waals open frameworks

Open-framework materials are constructed by connecting molecular components via strong bonds. It is generally believed that non-covalent interactions are too weak to hold the building blocks and generate stable open voids. Here we show that van der Waals interactions enable the construction of robust three-dimensional frameworks, referred to as van der Waals open frameworks (WaaFs). The key to successful synthesis of WaaFs is the use of octahedral metal-organic polyhedra with size larger than 2 nm as building blocks and their packing into a sparse diamond network with large extrinsic porosity. The well-defined faces composed of multiple planar moieties increase the intermolecular contact area to achieve an interaction energy above 400 kJ mol-1. We show that the WaaFs exhibit high thermal stability and high specific surface area as well as framework assembly with a reversible nature.

Formation of open ruthenium branched structures with highly exposed active sites for oxygen evolution reaction electrocatalysis

The formation of exposed active sites that have high activity and stability for oxygen evolution reaction (OER) catalysis is a significant opportunity for improving water electrolysers. Low-index facets surface Ru can achieve both high activity and stability for OER. Here, we present a new catalyst design where low-index faceted Ru branches are grown off the corners of Pt nanocubes, forming open Ru branched nanoparticles. This open branched structure, exposing low-index facets on its length-tunable branch, enables a high electrochemically active surface area (ECSA), achieving high activity and stability for OER. This design strategy and synthetic control provide a principle for achieving high-performance OER nanocatalysts.

Engineered Metal-Organic Frameworks for Targeted CRISPR/Cas9 Gene Editing

The development of precise and efficient delivery systems is pivotal for advancing CRISPR/Cas9 gene-editing technologies, particularly for therapeutic applications. Engineered metal-organic frameworks (MOFs) have emerged as a promising class of inorganic nonviral vectors, offering unique advantages such as tunable porosity, high cargo-loading capacity, and biocompatibility. This review explores the design and application of MOF-based nanoplatforms tailored for the targeted delivery of CRISPR/Cas9 components, aiming to enhance gene-editing precision and efficiency. By incorporating stimuli-responsive linkers and bioactive ligands, these MOFs enable controlled release of CRISPR/Cas9 payloads at the target site. Comparative discussions demonstrate superior performance of MOFs over conventional nonviral systems in terms of stability, transfection efficiency, and reduced off-target effects. Additionally, the intracellular trafficking mechanisms and the therapeutic potential of these platforms in preclinical models are discussed. These findings highlight the transformative potential of MOF-based delivery systems in overcoming the challenges associated with gene-editing technologies, such as immunogenicity and cytotoxicity, paving the way for their application in precision medicine. This review provides a blueprint for the integration of nanotechnology and genome editing, advancing the frontier of nonviral therapeutic delivery systems.

A uranyl-based metal-organic framework featuring an eight-connected U4L2 cage for guest capture

A novel (3,6)-connected uranyl-based MOF (IHEP-50) was synthesized by a judicious combination of UO22+ and polycarboxylic acid, 4,4',4'',4''',4'''',4'''''-(((1,3,5-triazine-2,4,6-triyl)tris(azanetriyl))hexakis(methylene))hexabenzoic acid (H6DTPCA). Two DTPCA6- ligands are connected together via four uranyl cations to form a lantern-shaped cage U4L2, which is further connected with other eight equivalent ones to form a 3D porous framework with two kinds of 1D channels. These large pore structures give it certain potential for guest molecule capture. Adsorption experiments indicate that IHEP-50 can selectively remove positively charged dyes over negatively charged and neutral ones. In addition, IHEP-50 demonstrates notable adsorption performance for gaseous iodine, achieving a maximum adsorption capacity of 253.5 mg g-1.

Toward Reversible Crystalline-to-Amorphous Guest-Induced Transitions in Manganese(III) Carboxylate Metal-Organic Frameworks

Metal-organic frameworks (MOFs) are an interesting class of inorganic/organic hybrid materials with a wide scope of applications. Although manganese is an abundant metal, the synthesis of Mn(III)-containing MOFs has not been widely studied due to the relative redox sensitivity of this species. We therefore investigated the self-oxidation of manganese(II) nitrate in the presence of aromatic dicarboxylic linkers in alcohols, discovering a series of new Mn(III)-MOFs. The obtained structures were analyzed through a combination of (synchrotron) X-ray diffraction and total scattering (pair distribution function analysis) experiments. In methanol, the syntheses led to new nonflexible members of the MIL-47/MIL-53 and MIL-69 families of MOFs, rare examples containing bridging methoxy anions. When using ethanol or 1-propanol, wine rack-like structures (named UcL-1 and UcL-2) with different MnII/MnIII secondary building units are obtained. These demonstrate intriguing reversible crystalline-to-crystalline and crystalline-to-amorphous transitions upon guest exchange and release. The latter process involves strong correlated and noncorrelated structural distortions, paired with the creation of coordinatively unsaturated MnIII sites. This work demonstrates that Mn(III)-containing carboxylate systems have the potential for the design of new functional MOF materials, including structures with tunable flexible behavior.

Space Exploration of Metal-Organic Frameworks in the Mesopore Regime

ConspectusThe past decades have witnessed the proliferation of porous materials offering high surface areas and the revolution in gas storage and separation, where metal-organic frameworks (MOFs) stand out as an important family. Alongside the pursuit of higher surface area, the increase in the size of guests, such as nanoparticles and biomolecules, has also led to the demand for larger space defined by the pores and cages within the MOF structure, from the conventional micropore regime (<2 nm) toward the mesopore regime (2-50 nm). Among the essential elements in the design of MOFs, molecular building blocks, their coordination and spatial arrangement, the chemistry for molecular design, and coordination bonds have become relatively mature, offering precise control of the shape and environment of the molecularly defined 3D cages; however, the correlation between the geometrical parameters and the size of polyhedrons describing the cages, concerning the spatial arrangement of building blocks, is much less explored.In this Account, we made efforts to associate actual cage size with the critical geometrical components, vertices, edges, connectivity, rings, and underlying polyhedrons, as well as the combination of components of various types in the design of MOFs. Several trends were found, such as influence from connectivity and expansion efficiency, offering insights into the construction of 3D cages in MOFs. This enables the creation of extremely large mesoporous cages in MOFs with an internal diameter up to 11.4 nm from relatively small building blocks. Furthermore, we discuss a strategy of partial removal or replacement of organic linkers to construct mesoporous cages from readily known topologies.All of the above efforts urged us to ask the following questions: Is there any limit in the sculpting of the 3D space from molecules? How large an area can one chemical bond support? The answer to these questions will deepen the knowledge of efficient utilization of chemical bonds in the sculpting of 3D spaces and guide the design of larger mesopores. Several general geometrical principals emerged: (1) Expansion efficiency and radius are positively correlated with the number of vertices. (2) Increase in the number of vertices and decrease of their connectivity favor the construction and expansion of large cages. (3) The boundary of the 3D space constructed by the chemical bonds is related to the polyhedron type and determined by the energy involved in crystallinity. Such principals are likely to be applicable also in the design of isolated cages in supramolecular chemistry. In addition to the structural design and synthesis, the applications of these mesoporous cages in MOFs are also summarized.

Coassembling Mesoporous Zeolitic Imidazolate Frameworks by Directed Reticular Chemistry

Conventional microporous zeolitic imidazolate frameworks (ZIFs) face limitations in mass transfer and pore accessibility when dealing with large guest molecules. Here, we describe a technique for the synthesis of mesoporous ZIFs (MesoZIFs) using a strategy we term directed reticular chemistry. MesoZIF-8 was prepared through solvent evaporation-induced coassembly of polystyrene-block-poly(ethylene oxide) (PS-b-PEO), ZIF-8 building blocks, and acetic acid (AcOH), followed by amine-facilitated crystallization of ZIF-8 in the interstices of PS-b-PEO micelles. AcOH prevents the fast coordination of ZIF-8 building blocks, avoiding phase separation during coassembly. The employed amine plays a crucial role in neutralizing the crystallization environment and further deprotonating the 2-methlyimizale linker to coordinate with zinc ions. Ink bottle-shaped mesopores with tunable mesopore sizes were created by adjusting the molecular weight of PS-b-PEO. Compared to microporous ZIF-8, MesoZIF-8 exhibited enhanced performance in Knoevenagel condensation reactions involving large reactants and hydrogen storage capacity. With this study, we establish an efficient approach for synthesizing MesoZIFs with highly accessible mesopores to enhance ZIF performance in targeted applications.

Merged-nets enumeration for the systematic design of multicomponent reticular structures

Rational design of intricate multicomponent reticular structures is often hindered by the lack of suitable blueprint nets. We established the merged-net approach, proffering optimal balance between designability and complexity, as a systematic solution for the rational assembly of multicomponent structures. In this work, by methodically mapping node-net relationships among 53 basic edge-transitive nets, we conceived a signature net map to identify merging net pairs, resulting in the enumeration of 53 merged nets. We developed a practical design algorithm and proposed more than 100 multicomponent metal-organic framework platforms. The effectiveness of this approach is commended by the successful synthesis of four classes of materials, which is based on merging three-periodic nets with the four possible net periodicities. The construction of multicomponent materials based on derived nets of merged nets highlights the potential of the merged-net approach in accelerating the discovery of intricate reticular materials.

Unlocking Efficiency: Minimizing Energy Loss in Electrocatalysts for Water Splitting

Catalysts play a crucial role in water electrolysis by reducing the energy barriers for hydrogen and oxygen evolution reactions (HER and OER). Research aims to enhance the intrinsic activities of potential catalysts through material selection, microstructure design, and various engineering techniques. However, the energy consumption of catalysts has often been overlooked due to the intricate interplay among catalyst microstructure, dimensionality, catalyst-electrolyte-gas dynamics, surface chemistry, electron transport within electrodes, and electron transfer among electrode components. Efficient catalyst development for high-current-density applications is essential to meet the increasing demand for green hydrogen. This involves transforming catalysts with high intrinsic activities into electrodes capable of sustaining high current densities. This review focuses on current improvement strategies of mass exchange, charge transfer, and reducing electrode resistance to decrease energy consumption. It aims to bridge the gap between laboratory-developed, highly efficient catalysts and industrial applications regarding catalyst structural design, surface chemistry, and catalyst-electrode interplay, outlining the development roadmap of hierarchically structured electrode-based water electrolysis for minimizing energy loss in electrocatalysts for water splitting.

A Multimetal Approach for the Reticulation of Iridium into Metal-Organic Framework Building Units

Noble metal elements are ubiquitous in our everyday life, from medical applications to electronic devices and synthetic chemistry. Iridium is one of the least abundant elements, and despite its scarcity, it remains essential for efficient and active catalytic processes. Consequently, the development of heterogeneous catalysts with the presence of active iridium sites is of enormous interest as it leads to the improvement of their recyclability and reusability. Here, we demonstrate a strategy to incorporate iridium atoms into metal-organic frameworks (MOFs), as part of their secondary building units (SBUs), resulting in robust and reusable materials with heterogeneous photocatalytic activity.

Ion Exchange-Mediated 3D Cross-Linked ZIF-L Superstructure for Flexible Electrochemical Energy Storage

Metal-organic frameworks (MOFs) are considered as a promising candidate for advancing energy storage owing to their intrinsic multi-channel architecture, high theoretical capacity, and precise adjustability. However, the low conductivity and poor structural stability lead to unsatisfactory rate and cycling performance, greatly hindering their practical application. Herein, we propose a sea urchin-like Co-ZIF-L superstructure using molecular template to induce self-assembly followed by ion exchange method, which shows improved conductivity, successive channels, and high stability. The ion exchange can gradually etch the superstructure, leading to the reconstruction of Co-ZIF-L with three-dimensional (3D) cross-linked ultrathin porous nanosheets. Moreover, the precise control of Co to Ni ratios can construct effective micro-electric field and synergistically enhance the rapid transfer of electrons and electrolyte ions, improving the conductivity and stability of CoNi-ZIF-L. The Co6.53Ni-ZIF-L electrode exhibits a high specific capacity (602 F g-1 at 1 A g-1) and long cycling stability (95.3 % retention after 4,000 cycles at 5 A g-1). The Co6.53Ni-ZIF-L//AC asymmetric flexible supercapacitor employing gel electrolyte also exhibits excellent cycling stability (93.3 % retention after 4000 cycles at 5 A g-1). This discovery provides valuable insights for electrode material selection and energy storage efficiency improvement.

Impact of Synthetic Variables on the Structural Diversity of TbIII-Carboxylate Frameworks: Gas Adsorption, Magnetism, and Organocatalysis Investigations

In this work, three unique TbIII-carboxylate frameworks with the formula {[Tb2(OH)2(H2O)2(abtc)]·2H2O}n (1), {[Tb2(abtc)1.5(H2O)3(DMA)]·H2O}n (2) and {[Tb3(abtc)2.5(H2O)4]·H3O}n (3), each displaying structural variations, have been successfully synthesized by the solvothermal reactions of Tb(NO3)3·6H2O with the azo-containing ligand 3,3',5,5'-azobenzene tetracarboxylic acid (H4abtc) under varying conditions. Detailed single-crystal X-ray diffraction (SC-XRD) analysis manifested a remarkable diversity in these structures, demonstrating various coordination patterns of TbIII-metal nodes with the carboxylate groups of the organic linker, which contributed to the generation of intricate three-dimensional (3D) coordination networks with remarkable chemical resistance. Furthermore, frameworks 2 and 3, characterized by porous networks containing two and three independent TbIII-metal nodes, respectively, were both demonstrated to be efficient heterogeneous catalysts toward the cyanosilylation of imines under mild conditions with excellent reusability. In addition, direct current (Dc) magnetic susceptibility measurements conducted on frameworks 1, 2, and 3 indicated that there were obvious antiferromagnetic interactions among the TbIII-metal nodes, which suggests the involvement of intricate intra- and intertrimer exchange channels, adding another fascinating dimension to their physical properties.

A comprehensive review on the enantiomeric separation of chiral drugs using metal-organic frameworks

Chiral drugs play an important role in modern medicine, but obtaining pure enantiomers from racemic mixtures can pose challenges. When a drug is chiral, only one enantiomer (eutomer) typically exhibits the desired pharmacological activity, while the other (distomer) may be biologically inactive or even toxic. Racemic drug formulations introduce additional health risks, as the body must still process the inactive or detrimental enantiomer. Some distomers have also been linked to teratogenic effects and unwanted side effects. Therefore, developing efficient and scalable methods for separating chiral drugs into their pure enantiomers is critically important for improving patient safety and outcomes. Metal-organic frameworks (MOFs) show promise as novel materials for chiral separation due to their highly tunable structures and interactions. This review summarizes recent advancements in using MOFs for chromatographic and spectroscopic resolution of drug enantiomers. Both the opportunities and limitations of MOF-based separation techniques are discussed. A thorough understanding of these methods could aid the continued development of pure enantiomer formulations and help reduce health risks posed by racemic drug mixtures.

Thorium Cluster Synthesized by a Solvent-Free Flux Approach: The Richest Coordination Diversity and Application Exploration

The renaissance of research interests in actinide oxo clusters in the past decade arises from both the concerns of radioactive contamination and their potential utility as nanoscale materials. Compared to the uranium cluster, the thorium (Th) cluster shows less coordination variation. Herein, we presented a unique Th cluster (ThC-1) that exhibits the most diverse coordination chemistry found within a single Th cluster via a solvent-free flux synthesis approach. The melt triazole not only offers a unique solvation environment that may be responsible for the coordination diversity in ThC-1 but also represents the first nitrogen-donor capping ligand in Th clusters. The potential utility of ThC-1 as a heterogeneous catalyst was also explored for a classical CO2 cycloaddition reaction. This work offers a novel approach in synthesizing Th clusters, broadening the realm of the structural diversity of Th.

Parsimonious Topology Based on Frank-Kasper Polyhedra in Metal-Organic Frameworks

A new topology previously unknown in metal-organic frameworks (MOFs) provides an important clue to uncovering a new series of polyhedral MOFs. We report a novel MOF crystallized in a parsimonious mep topology based on Frank-Kasper (FK) polyhedra. The distribution of angles in a tetrahedral arrangement (T-O-T) is crucial for the formation of FK polyhedra in mep topology. This finding led us to investigate the T-O-T angle distribution in related zeolites and zeolitic imidazolate frameworks (ZIFs). Unlike zeolites, it is extremely difficult to achieve high T-O-T angles in ZIFs, which prevents the formation of some FK topologies. Density functional theory (DFT) total energy calculations support a correlation between T-O-T angles and the feasibility of new tetrahedron-based FK frameworks. This result may lead to innovative ways of accessing new cellular topologies by simple chemical tweaking of T-O-T angles.

Avoiding the Kinetic Inertness of Chromium Ions Using a Coordination Substitution Strategy for the Rapid Synthesis of Chromium-Based Metal-Organic Frameworks

Chromium-based metal-organic frameworks (Cr-MOFs) are very attractive in a wide range of applications due to their robustness and high porosity. However, the kinetic inertness of chromium ions results in the synthesis of Cr-MOFs often taking prolonged reaction times, which limit their industrial applications. Herein, we report a novel synthesis strategy based on coordination substitution, which overcomes the kinetic inertness of chromium ions and can synthesize Cr-MOFs in a shorter time. The versatility of this strategy has been demonstrated by producing several known Cr-MOFs, such as TYUT-96Cr, MIL-100Cr, MIL-101Cr, and MIL-53Cr. PXRD, SEM, TEM, 77 K N2 adsorption, and TGA have proved that the Cr-MOFs synthesized using this new strategy have good crystallinity, high porosity, and excellent thermal stability. The synthesis mechanism was investigated using theoretical calculations.

Mining for Metal-Organic Systems: Chemistry Frontiers of Th-, U-, and Zr-Materials

The conceptual framework presented in this Perspective overviews the design principles of innovative thorium-based materials that could address urgent needs of the medicinal, nuclear energy, and waste remediation sectors from the lens of zirconium and uranium analogs. We survey the intersections of Zr, Th, and U chemistry with a focus on how the intrinsic behavior of each metal translates to broader material properties, including, but not limited to, structural and topological diversity, preferential metal-ligand binding, and reactivity. On the example of several classes of materials, including organometallic complexes, polyoxometalates, and the primary focus of this Perspective, metal-organic frameworks (MOFs), the design principles that govern the preparation of Zr-, Th-, and U-compounds, including oxophilicity, variation in oxidation states, and stable coordination environments have been considered. Further, we highlight how the impact of the mentioned variables may shift throughout the progression from discrete molecular systems to extended structures. We discuss the common assumption that zirconium-organic materials are typically considered a close analog of thorium-based congeners in areas such as material design and preparation. Through consideration of fundamental chemistry principles, we shed light on the relationships between Zr-, Th-, and U-based materials and highlight how a critical analysis of their distinct properties can be used to target a desired material performance. As a result, we provide a detailed understanding of Th-based materials chemistry by anchoring their fundamental properties between two well-studied reference points, zirconium- and uranium-containing analogs.

Copper-Vit B3 MOF preparation, characterization and catalytic evaluation in a one-pot synthesis of benzoxanthenones with docking validation as anti H. pylori

Copper-Vit B3 MOF was successfully prepared by efficient and eco hydrothermal method. The prepared MOF was characterized as a tetragonal crystal copper-MOF nanoparticles by FTIR, SEM, TEM, EDX and XRD. The prepared nanoparticles were used as an effective, inexpensive and low-toxic catalyst in the one-pot synthesis of some new benzoxanthenone derivatives. As example 4-(9,9-dimethyl-11-oxo-8,10,11,12-tetrahydro-9H-benzo[a]xanthen-12-yl)phenyl benzoate (4h) was synthesized in high yield 92%. The MOF catalyst's role is activating the nucleophilic attack by increasing the carbonyl polarization, and this generally improves the reaction time, which ranges between 20-60 minutes and products' yields ranging between 80-92%. Prepared compounds (4a-4j) undergo molecular docking scanning as Helicobacter pylori type II dehydroquinase inhibitors, and the data obtained showed that there are three promises of the prepared compounds 4d, 4e, 4h and 4j compared with amoxicillin.

Uranyl-Tc(VII)/Tc(V) hybrid clusters

Pertechnetate (99TcVIIO4-), reduced Tc, and actinides co-exist in spent nuclear fuel and legacy wastes. They co-transport in fuel reprocessing and waste disposal scenarios, necessitating an understanding of co-speciation. Here, we report five new molecular cluster/framework structures with pentameric and tetrameric uranyl building units decorated by TcO4-/ReO4- oxoanions, or fused with the reduced technetyl cation Tc(V)O. The latter, obtained by Tc auto-reduction (without the intentional introduction of a reducing environment), broadens the basis for Tc-reduction and the burgeoning polyoxometalate-like behavior of technetium.

Immobilization of Amino-site into a Pore-Partitioned Metal-Organic Framework for Highly Efficient Separation of Propyne/Propylene

Adsorptive separation of propyne/propylene (C3H4/C3H6) is a crucial yet complex process, however, it remains a great difficulty in developing porous materials that can meet the requirements for practical applications, particularly with an exceptional ability to bind and store trace amounts of C3H4. Functionalization of pore-partitioned metal-organic frameworks (ppMOFs) is methodically suited for this challenge owing to the possibility of dramatically increasing binding sites on highly porous and confined domains. We here immobilized Lewis-basic (-NH2) and Lewis-acidic (-NO2) sites on this platform. Along with an integrated nature of high uptake of C3H4 at 1 kPa, high uptake difference of C3H4-C3H6, moderated binding strength, promoted kinetic selectivity, trapping effect and high stability, the NH2-decorated ppMOF (NTU-100-NH2) can efficiently produce polymer-grade C3H6 (99.95 %, 8.3 mmol ⋅ g-1) at room temperature, which is six times more than the NO2-decorated crystal (NTU-100-NO2). The in situ infrared spectroscopy, crystallographic analysis, and sequential blowing tests showed that the densely packed amino group in this highly porous system has a unique ability to recognize and stabilize C3H4 molecules. Moving forward, the strategy of organic functionalization can be extended to other porous systems, making it a powerful tool to customize advanced materials for challenging tasks.

Synergistic Nitrogen Binding Sites in a Metal-Organic Framework for Efficient N2 /O2 Separation

Porous materials with d3 electronic configuration open metal sites have been proved to be effective adsorbents for N2 capture and N2 /O2 separation. However, the reported materials remain challenging to address the trade-off between adsorption capacity and selectivity. Herein, we report a robust MOF, MIL-102Cr, that features two binding sites, can synergistically afford strong interactions for N2 capture. The synergistic adsorption site exhibits a benchmark Qst of 45.0 kJ mol-1 for N2 among the Cr-based MOFs, a record-high volumetric N2 uptake (31.38 cm3  cm-3 ), and highest N2 /O2 selectivity (13.11) at 298 K and 1.0 bar. Breakthrough experiments reveal that MIL-102Cr can efficiently capture N2 from a 79/21 N2 /O2 mixture, providing a record 99.99 % pure O2 productivity of 0.75 mmol g-1 . In situ infrared spectroscopy and computational modelling studies revealed that a synergistic adsorption effect by open Cr(III) and fluorine sites was accountable for the strong interactions between the MOF and N2 .

Double-stranded metallo-triangles: from anion-templated nonanuclear to cation-templated tetraicosanuclear dysprosium clusters

Two double-stranded metallo-triangles, Dy9 and Dy24, with hexaple-C10H7PO32- bridges were constructed, and their magnetic properties were explored. Compared with the field-induced relaxation phenomenon of Dy9 templated with a chloride anion, Dy24 templated with a sodium cation exhibited zero-field single-molecule-magnet behavior.

Crystal structure and photocatalytic activity of luminescent 3D-Supramolecular metal organic framework of dysprosium

A 3D supramolecular metal organic framework of dysprosium has been fabricated through a facile hydrothermal procedure with the ligand, 2,6-naphthalene disulphonic acid and the co-ligand, 4,4'-bipyridine. The MOF has been characterized as [C60H81DyN8O30S4] by routine analytical procedures. SXRD studies of the MOF show the existence of a hydrogen-bonded 3D supramolecular structure with high porosity. It crystallizes in monoclinic space group P21/n with unit cell parameters, a = 16.5424(6) Å, b = 37.0052(14) Å, c = 24.4361(9) Å, β = 100.7410°, α = γ = 90°. The Dy-MOF has eight coordinated water molecules around the metal centre and exhibits square anti-prismatic geometry. The band gap is 3.11 eV. The degradation experiments under visible light confirmed that Dy-MOF can act as a photocatalyst. Addition of hydrogen peroxide remarkably increases the degradation efficiency of the MOF through an advanced oxidation process. The newly synthesized MOF produced sharp emission peaks characteristic of dysprosium ion.

The effective regulation of heterogeneous N-heterocyclic carbenes: structures, electronic properties and transition metal adsorption

Heterogeneous N-heterocyclic carbene materials have attracted increasing interest in the fields of materials science and catalysis due to their unique properties and potential applications. However, current heterogeneous systems primarily focus on a single class of carbene. In this work, we simultaneously introduce two classes of typical five-membered carbenes into a graphene lattice, forming a series of novel two-dimensional heterogeneous N-heterocyclic carbene nanomaterials (2D-NCMs) composed of multiple carbenes. First-principles calculations demonstrate the thermodynamic stability of the designed 2D-NCMs, as well as their diverse electronic properties ranging from metallic to semiconducting. The incorporation of carbenes in the 2D-NCMs enables them to adsorb both acidic BCl3 and basic CO molecules, thus exhibiting unique amphoteric properties. Furthermore, the 2D-NCMs exhibit remarkable adsorption capacities for ten transition metals, highlighting their promising potential for future catalytic applications. By adjusting the proportions of the two classes of carbenes, we can effectively regulate the electronic properties and adsorption capacities of small molecules and transition metals in the 2D-NCMs. This study presents a novel strategy for designing and regulating the properties of heterogeneous N-heterocyclic carbenes, offering significant implications in the fields of catalysis and materials science.

Gold(I)-Organic Frameworks as Catalysts for Carboxylation of Alkynes with CO2

Construction of gold-based metal-organic frameworks (Au-MOFs) would bring the merits of gold chemistry into MOFs. However, it still remains challenging because gold cations are easily reduced to metallic gold under solvothermal conditions. Herein, we present the first example of Au-MOFs prepared from the networking of cyclic trinuclear gold(I) complexes by formal transimination reaction in a rapid (<15 min) and scalable (up to 1 g) fashion under ambient condition. The Au-MOFs feature uniform porosity, high crystallinity, and superior chemical stability toward base (i.e., 20 M NaOH). With open Au(I) sites in the skeleton, the Au-MOFs as heterogeneous catalysts delivered good performance and substrate tolerance for the carboxylation reactions of alkynes with CO2. This work demonstrates a facile approach to reticularly synthesize Au-MOFs by combining the coordination and dynamic covalent chemistry.

Mesoporous Metal-Organic Frameworks for Catalytic RNA Deprotection and Activation

A metal-organic framework (MOF) with mespores (2 to 50 nm) allows the inclusion of large biomolecules, such as nucleic acids. However, chemical reaction on the nucleic acids, to further regulate their bioactivity, is yet to be demonstrated within MOF pores. Here, we report the deprotection of carbonate protected RNA molecules (21 to 102 nt) to restore their original activity using a MOF as a heterogeneous catalyst. Two MOFs, MOF-626 and MOF-636 are designed and synthesized, with mesopores of 2.2 and 2.8 nm, respectively, carrying isolated metal sites (Ni, Co, Cu, Pd, Rh and Ru). The pores favor the entrance of RNA, while the metal sites catalyze C-O bond cleavage at the carbonate group. Complete conversion of RNA is achieved by Pd-MOF-626, 90 times more efficiently than Pd(NO3 )2 . MOF crystals are also removable from the aqueous reaction media, leaving a negligible metal footprint, 3.9 ppb, only 1/55 of that using homogeneous Pd catalysts. These features make MOF potentially suited for bioorthogonal chemistry.

Influence of Linker Identity on the Photochemistry of Uranyl-Organic Frameworks

While uranyl-based metal-organic frameworks (MOFs) boast impressive photocatalytic abilities, significant questions remain regarding their excitation pathways and methods to fine-tune their performance due to the lack of information regarding heterogeneous uranyl catalysis. Herein, we investigated how linker identity and photoexcitation impact uranyl photocatalysis when the uranyl coordination environment remains constant. Toward this end, we prepared three uranyl-based MOFs (NU-1301, NU-1307, and ZnTCPP-U2) and then examined the structural and photochemical properties of each through X-ray diffraction, X-ray absorption, and photoluminescence. We then correlated our observations to the photocatalytic performance for fluorination of cyclooctane. The excitation profile from NU-1301 and NU-1307 exhibited spin-forbidden linker transitions and uranyl vibronic progressions, with uranyl excitation and emission being most dominant in NU-1301. Consequently, NU-1301 was a more active photocatalyst than NU-1307. In contrast, the excitation profile from ZnTCPP-U2 contained transitions associated with the porphyrin linker exclusively. Photocatalytic activity from ZnTCPP-U2 significantly underperformed in comparison to that of the other two MOFs. These data suggest that linkers' photophysical properties can be used to predict the photocatalytic behavior of uranyl-containing MOFs.

Nanotubule inclusion in the channels formed by a six-fold interpenetrated, triperiodic framework

When reacted together with uranyl ions under solvo-hydrothermal conditions, a bis(pyridiniumcarboxylate) zwitterion (L) and tricarballylic acid (H3tca) give the complex [NH4]2[UO2(L)2][UO2(tca)]4·2H2O (1). The two ligands are segregated into different units, an anionic nanotubule for tca3- and a six-fold interpenetrated cationic framework with lvt topology for L. The entangled framework defines large channels which contain the square-profile nanotubules. Complex 1 has a photoluminescence quantum yield of 19% and its emission spectrum shows the superposition of the signals due to the two independent species.

Extremely Large 3D Cages in Metal-Organic Frameworks for Nucleic Acid Extraction

Three-dimensional (3D) cages in the mesopore regime (2-50 nm) assembled from molecular building blocks are highly desirable in biological applications; however, their synthesis in crystalline form is quite challenging, as well as their structure characterization. Here, we report the synthesis of extremely large 3D cages in MOF crystals, with internal cage sizes of 6.9, and 8.5 nm in MOF-929; 9.3 and 11.4 nm in MOF-939, in cubic unit cells, a = 17.4 and 22.8 nm, respectively. These cages are constructed from relatively short organic linkers with the lengths of 0.85 and 1.3 nm, where the influence from molecular motion is minimized, thus favoring their crystallization. A 0.45 nm linker length elongation leads to a maximum 2.9 nm increase in cage size, giving a supreme efficiency in cage expansion. The spatial arrangements of these 3D cages were visualized by both X-ray diffraction and transmission electron microscopy. The efforts to obtain these cages in crystals pushed forward the size boundary for the construction of 3D cages from molecules and also exploited the limit of the area in space possibly supported per chemical bond, where the expansion efficiencies of the cages were found to play a critical role. These extremely large 3D cages in MOFs were useful in the complete extraction of long nucleic acid, such as total RNA and plasmid from aqueous solution.

Energy-structure-property relationships in uranium metal-organic frameworks

Located at the foot of the periodic table, uranium is a relatively underexplored element possessing rich chemistry. In addition to its high relevance to nuclear power, uranium shows promise for small molecule activation and photocatalysis, among many other powerful functions. Researchers have used metal-organic frameworks (MOFs) to harness uranium's properties, and in their quest to do so, have discovered remarkable structures and unique properties unobserved in traditional transition metal MOFs. More recently, (e.g. the last 8-10 years), theoretical calculations of framework energetics have supplemented structure-property studies in uranium MOFs (U-MOFs). In this Perspective, we summarize how these budding energy-structure-property relationships in U-MOFs enable a deeper understanding of chemical phenomena, enlarge chemical space, and elevate the field to targeted, rather than exploratory, discovery. Importantly, this Perspective encourages interdisciplinary connections between experimentalists and theorists by demonstrating how these collaborations have elevated the entire U-MOF field.

Advances of Electroactive Metal-Organic Frameworks

The preparation of electroactive metal-organic frameworks (MOFs) for applications of supercapacitors and batteries has received much attention and remarkable progress during the past few years. MOF-based materials including pristine MOFs, hybrid MOFs or MOF composites, and MOF derivatives are well designed by a combination of organic linkers (e.g., carboxylic acids, conjugated aromatic phenols/thiols, conjugated aromatic amines, and N-heterocyclic donors) and metal salts to construct predictable structures with appropriate properties. This review will focus on construction strategies of pristine MOFs and hybrid MOFs as anodes, cathodes, separators, and electrolytes in supercapacitors and batteries. Descriptions and discussions follow categories of electrochemical double-layer capacitors (EDLCs), pseudocapacitors (PSCs), and hybrid supercapacitors (HSCs) for supercapacitors. In contrast, Li-ion batteries (LIBs), Lithium-sulfur batteries (LSBs), Lithium-oxygen batteries (LOBs), Sodium-ion batteries (SIBs), Sodium-sulfur batteries (SSBs), Zinc-ion batteries (ZIBs), Zinc-air batteries (ZABs), Aluminum-sulfur batteries (ASBs), and others (e.g., LiSe, NiZn, H⁺ , alkaline, organic, and redox flow batteries) are categorized for batteries.

Record Ultralarge-Pores, Low Density Three-Dimensional Covalent Organic Framework for Controlled Drug Delivery

The unique structural characteristics of three-dimensional (3D) covalent organic frameworks (COFs) like high surface areas, interconnected pore system and readily accessible active sites render them promising platforms for a wide set of functional applications. Albeit promising, the reticular construction of 3D COFs with large pores is a very demanding task owing to the formation of interpenetrated frameworks. Herein we report the designed synthesis of a 3D non-interpenetrated stp net COF, namely TUS-64, with the largest pore size of all 3D COFs (47 Å) and record-low density (0.106 g cm^-3 ) by reticulating a 6-connected triptycene-based linker with a 4-connected porphyrin-based linker. Characterized with a highly interconnected mesoporous scaffold and good stability, TUS-64 shows efficient drug loading and controlled release for five different drugs in simulated body fluid environment, demonstrating the competency of TUS-64 as drug nanocarriers.

Single-Crystal Superstructures via Hierarchical Assemblies of Giant Rubik's Cubes as Tertiary Building Units

Intricate superstructures possess unusual structural features and promising applications. The preparation of superstructures with single-crystalline nature are conducive to understanding the structure-property relationship, however, remains an intriguing challenge. Herein we put forward a new hierarchical assembly strategy towards rational and precise construction of intricate single-crystal superstructures. Firstly, two unprecedented superclusters in Rubik's cube's form with a size of ≈2×2×2 nm³ are constructed by aggregation of eight {Pr₄ Sb₁₂ } oxohalide clusters as secondary building units (SBUs). Then, the Rubik's cubes further act as isolable tertiary building units (TBUs) to assemble diversified single-crystal superstructures. Importantly, intermediate assembly states are captured, which helps illustrate the evolution of TBU-based superstructures and thus provides a profound understanding of the assembly process of superstructures at the atomic level.

f-block MOFs: A Pathway to Heterometallic Transuranics

A novel series of heterometallic f-block-frameworks including the first examples of transuranic heterometallic ²³⁸ U/²³⁹ Pu-metal-organic frameworks (MOFs) and a novel monometallic ²³⁹ Pu-analog are reported. In combination with theoretical calculations, we probed the kinetics and thermodynamics of heterometallic actinide(An)-MOF formation and reported the first value of a U-to-Th transmetallation rate. We concluded that formation of uranyl species could be a driving force for solid-state metathesis. Density of states near the Fermi edge, enthalpy of formation, band gap, proton affinity, and thermal/chemical stability were probed as a function of metal ratios. Furthermore, we achieved 97 % of the theoretical maximum capacity for An-integration. These studies shed light on fundamental aspects of actinide chemistry and also foreshadow avenues for the development of emerging classes of An-containing materials, including radioisotope thermoelectric generators or metalloradiopharmaceuticals.

Metal-organic frameworks as chemical nanoreactors for the preparation of catalytically active metal compounds

Since the emergence of metal-organic frameworks (MOFs), a myriad of thrilling properties and applications, in a wide range of fields, have been reported for these materials, which mainly arise from their porous nature and rich host-guest chemistry. However, other important features of MOFs that offer great potential rewards have been only barely explored. For instance, despite the fact that MOFs are suitable candidates to be used as chemical nanoreactors for the preparation, stabilization and characterization of unique functional species, that would be hardly accessible outside the functional constrained space offered by MOF channels, only very few examples have been reported so far. In particular, we outline in this feature recent advances in the use of highly robust and crystalline oxamato- and oxamidato-based MOFs as reactors for the in situ preparation of well-defined catalytically active single atom catalysts (SACS), subnanometer metal nanoclusters (SNMCs) and supramolecular coordination complexes (SCCs). The robustness of selected MOFs permits the post-synthetic (PS) in situ preparation of the desired catalytically active metal species, which can be characterised by single-crystal X-ray diffraction (SC-XRD) taking advantage of its high crystallinity. The strategy highlighted here permits the always challenging large-scale preparation of stable and well-defined SACs, SNMCs and SCCs, exhibiting outstanding catalytic activities.

Effectively Decontaminating Protein-Bound Uremic Toxins in Human Serum Albumin Using Cationic Metal-Organic Frameworks

In the field of replacement of conventional dialysis treatment, searching superior materials for removal of protein-bound uremic toxins is a challenge on account of strong interactions between proteins and uremic toxins. Herein, we first adopted cationic metal-organic frameworks (MOFs), ZJU-X6 and ZJU-X7, as sorbents to decontaminate uremic toxins (p-cresyl sulfate and indoxyl sulfate). ZJU-X6 and ZJU-X7 exhibited innate advantage for sequestration of uremic toxins by utilizing a positive charge framework with exchangeable anions. Especially, ZJU-X6 showed a higher sorption capacity and faster sorption kinetics than those of most reported materials. Moreover, the cationic MOF materials could selectively remove uremic toxins even if in the presence of competitive chloride ions and proteins. Meanwhile, pair distribution function (PDF) and density functional theory (DFT) were employed to elucidate the sorption mechanism between uremic toxins and sorbents. This work suggests an attractive avenue for constructing new types of sorbents to eliminate uremic toxins for uremia treatment.

Creating High-Number Defect Sites through a Bimetal Approach in Metal-Organic Frameworks for Boosting Trace SO2 Removal

Herein, we represent a bimetallic approach to enhance the defect number, leading to eight defect sites per node in a metal-organic framework, showing both a higher SO₂ adsorption capacity and higher SO₂/CO₂ selectivity. The results can be further strongly supported by density functional theory calculations.

Template-Mediated Synthesis of Hierarchically Porous Metal–Organic Frameworks for Efficient CO2/N2 Separation

Carbon dioxide (CO₂) is generally unavoidable during the production of fuel gases such as hydrogen (H₂) from steam reformation and syngas composed of carbon monoxide (CO) and hydrogen (H₂). Efficient separation of CO₂ from these gases is highly important to improve the energetic utilization efficiency and prevent poisoning during specific applications. Metal–organic frameworks (MOFs), featuring ordered porous frameworks, high surface areas and tunable pore structures, are emerging porous materials utilized as solid adsorbents for efficient CO₂ capture and separation. Furthermore, the construction of hierarchical MOFs with micropores and mesopores could further promote the dynamic separation processes, accelerating the diffusion of gas flow and exposing more adsorptive pore surface. Herein, we report a simple, efficient, one-pot template-mediated strategy to fabricate a hierarchically porous CuBTC (CuBTC-Water, BTC = 1,3,5-benzenetricarboxylate) for CO₂ separation, which demonstrates abundant mesopores and the superb dynamic separation ability of CO₂/N₂. Therefore, CuBTC-Water demonstrated a CO₂ uptake of 180.529 cm³ g⁻¹ at 273 K and 1 bar, and 94.147 cm³ g⁻¹ at 298 K and 1 bar, with selectivity for CO₂/N₂ mixtures as high as 56.547 at 273 K, much higher than microporous CuBTC. This work opens up a novel avenue to facilely fabricate hierarchically porous MOFs through one-pot synthesis for efficient dynamic CO₂ separation.

Enhancing photosensitivity via the assembly of a uranyl coordination polymer

Synergistic assembly of uranyl centres and luminescent 2,6-bis(pyrazol-1-yl)pyridine-4-carboxylates (bppCOOH) gives rise to a uranyl coordination polymer, namely U-bppCOO, which exhibits a luminescence quenching response toward UV or X-ray irradiation doses. Notably, the photosensitivity of U-bppCOO has been significantly enhanced via metal-ligand assembly compared with that of the naked bppCOOH ligand.

Combined and Single Doxorubicin/Naproxen Drug Loading and Dual-Responsive pH/Ultrasound Release from Flexible Metal-Organic Framework Nanocarriers

In this study, the flexible aluminum-based MIL-53(Al) metal-organic framework was loaded with doxorubicin (DOX) and naproxen (NAP) and was examined as a promising pH/ultrasound dual-responsive drug delivery system. The two drugs were encapsulated in MIL-53(Al) individually to produce the DOX@MIL-53(Al) and NAP@MIL-53(Al) nanocarriers. They were also encapsulated as a dual-drug formulation to produce the DOX* + NAP*@MIL-53(Al) nanocarrier. The MOF nanoparticles were characterized using the Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), and Dynamic Light Scattering (DLS) techniques. In the case of the DOX@MIL, the nanocarriers’ drug Encapsulation Efficiency (EE) and Encapsulation Capacity (EC) were 92% and 16 wt.%, respectively, whereas, in the case of NAP@MIL-53(Al), the average NAP EE and EC were around 97.7% and 8.5 wt.%, respectively. On the other hand, in the DOX* + NAP*@MIL-53(Al) nanoparticles, the average DOX* EE and EC were 38.9% and 6.22 wt.%, respectively, while for NAP*, the average EE and EC were 70.2% and 4.49 wt.%, respectively. In vitro release experiments demonstrated the good pH and Ultrasound (US) dual-responsiveness of these nanocarriers, with a maximum US-triggered DOX and NAP release, at a pH level of 7.4, of approximately 53% and 95%, respectively. In comparison, the measured release was around 90% and 36% at pH 5.3 for DOX and NAP, respectively. In the case of the dualdrug formulation, the nanocarrier displayed similar pH/US dual-responsive behavior. Finally, the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) results confirmed the biocompatibility and low cytotoxicity of MIL-53(Al) at concentrations up to 1000 μg/ml.

The topology of crystalline matter

In this chapter an overview is given in which way framework-like crystalline compounds can be regarded as nets, how a net is derived out of a particular crystal structure, what nets actually are, how they can be appropriately described, what the characteristics of nets are, and how this topological approach helps to categorize framework compounds. Finally the term reticular chemistry is explained and a number of examples are given how the topology-guided approach opens up new possibilities to intentionally develop new framework structures on a rational basis.

Design Rules of Hydrogen-Bonded Organic Frameworks with High Chemical and Thermal Stabilities

Hydrogen-bonded organic frameworks (HOFs), self-assembled from strategically pre-designed molecular tectons with complementary hydrogen-bonding patterns, are rapidly evolving into a novel and important class of porous materials. In addition to their common features shared with other functionalized porous materials constructed from modular building blocks, the intrinsically flexible and reversible H-bonding connections endow HOFs with straightforward purification procedures, high crystallinity, solution processability, and recyclability. These unique advantages of HOFs have attracted considerable attention across a broad range of fields, including gas adsorption and separation, catalysis, chemical sensing, and electrical and optical materials. However, the relatively weak H-bonding interactions within HOFs can potentially limit their stability and potential use in further applications. To that end, this Perspective highlights recent advances in the development of chemically and thermally robust HOF materials and systematically discusses relevant design rules and synthesis strategies to access highly stable HOFs.

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.

Role of Lewis Acid Metal Centers in Metal–Organic Frameworks for Ultrafast Reduction of 4-Nitrophenol

Metal–Organic Frameworks (MOFs) can be a good alternative to conventional catalysts because they are non-toxic and can be selective without compromising efficiency. Nano MOFs such as UiO-66 have proven themselves to be competitive in the catalytic family. In this study, we report the excellent catalytic behavior of UiO-66 MOF in the reduction of a model reaction: 4-Nitrophenol (4-NP) to 4-Aminophenol (4-AP) over MOF-5 (Zn-BDC) and MIL-101 (Fe-BDC). Nano UiO-66 crystals were synthesized by a hydrothermal process and characterized by Powder X-ray Diffraction, Diffused Reflectance UV-Vis spectroscopy, Scanning Electron Microscopy, and Transmission Electron Microscopy. The catalysts’ performance during the hydrogenation reduction reaction from 4-NP to 4-AP was investigated in the presence of a reducer, NaBH4. The UiO-66 nano crystals exhibited excellent catalytic behavior owing to its large surface area and Lewis acidic nature at the metal nodes. Furthermore, UiO-66 showed excellent recyclability behavior, verified during repeated consecutive use in a sequence. The catalyst yielded similar catalytic behavior during the reduction of nitrophenols at each cycle, which is a novel finding.