Size-Controlled Synthesis of Luminescent Few-Atom Silver Clusters via Electron Transfer in Isostructural Redox-Active Porous Ionic Crystals

In Situ Reducible Ionic Frameworks for Dual-Site and Photothermal Catalysis

Ionic frameworks (IFs), characterized by ionic bonds and periodic framework structures, find extensive applications in several fields. However, the inherent high bond energy of ionic bonds often leads to the formation of close-packed structures rather than open frameworks. Consequently, the selection of suitable building units is pivotal for the successful synthesis of IFs. Utilizing the large size and negative charge of polyoxometalates (POMs), along with their combination with metal cations, offers an effective approach for constructing IFs. In this study, 2D IFs are fabricated using {Na4O18} cluster formed by sodium ions and Anderson-type polyanions. Polyoxovanadates are integrated into the framework voids, resulting in a uniform distribution of the two clusters. The catalytic performance of IFs is evaluated through two reactions, revealing that two clusters IFs act as dual-site catalysts, thereby enhancing reaction efficiency. In the presence of strong reductants, polyoxovanadates undergo partial reduction, inducing a single-crystal-to-single-crystal transformation. The reduced IFs display pronounced photothermal conversion capabilities and serve as efficient photothermal-catalytic agents for the cycloaddition of epoxides and carbon dioxide. This research not only enhances the structural diversity of IFs and achieves uniform cluster distribution but also pioneeringly demonstrates the in situ reduction of IFs and their application in near-infrared photothermal catalysis.

Selective Separation of Thorium from Rare Earth Ions Using Bisphosphonate-Functionalized Ionic Single Crystals Co-Self-Assembled via π-π and Ionic Interactions

In this study, new bisphosphonate-functionalized ionic organic crystals (IOCs) were developed by π-π and ionic interactions with the high oxygen content of the phosphonic acid group. Meanwhile, this novel material achieved an extremely high selectivity of Th adsorption with a saturation adsorption capacity of 426 mg/g. In addition, the heat resistance (400 °C) and the recyclability (more than five cycles) make the IOCs economical for their extraordinary stability. Moreover, we use single-crystal X-ray diffraction to determine the monomer connections and the ionic bonds. We used kinetic fitting and X-ray photoelectron spectroscopy testing to explain the adsorption mechanism, which reveals a monolayer adsorption process with a distinct O-Th bond post-adsorption. This study not only gave an example to develop new ionic single crystals based on different functional groups but also expanded the potential application to use these new types of nanomaterials.

Recent Advances in Polyoxometalate‒Metal Nanocluster Hybrids

Polyoxometalates (POMs) are structurally well-defined anionic metal-oxo clusters with diverse structural forms and distinctive physicochemical properties, including acidity/basicity, redox activity, and optical behavior. Over the past two decades, POMs have garnered increasing attention in metal nanocluster synthesis owing to their ability to impart unique structural and functional characteristics to these compounds. Initially, research in this field primarily focused on hybrid materials composed of POMs and metal nanoclusters stabilized by organic ligands. However, more recently, studies have demonstrated that POMs can themselves act as effective stabilizing ligands for the synthesis of atomically precise metal nanoclusters. These POM-stabilized metal nanoclusters exhibit synergistic and cooperative properties of metal nanocluster and POM components, enabling novel applications in fields such as catalysis, photochemistry, sensing, and electrochemistry. Notably, recent investigations into POM-metal nanocluster hybrids have demonstrated their potential as atomically precise counterparts to metal nanoparticle catalysts supported on bulk metal oxides, exhibiting the unique cooperative catalysis. This review provides a concise overview of POM‒metal nanocluster hybrids, with an emphasis on recent advancements in synthetic methodologies, properties, and applications. Additionally, solid-state synthetic strategies leveraging the rigid structures and redox properties of POMs for the controlled formation of metal nanoclusters are discussed.

Co-Assembly of Polyoxometalates and Porphyrins as Anode for High-Performance Lithium-Ion Batteries

Polyoxometalates (POMs) have been considered one of the most promising anode candidates for lithium-ion batteries (LIBs) in virtue of their high theoretical capacity and reversible multielectron redox properties. However, the poor intrinsic electronic conductivity, low specific surface area, and high solubility in organic electrolytes hinder their widespread applications in LIBs. Herein, a novel hybrid nanomaterial is synthesized by co-assembling POMs and porphyrins (PMo12/CoTPyP) through a facile solvothermal method. The POM clusters are stabilized by porphyrin units through electrostatic interactions, which simultaneously realize the uniform dispersion of POMs and porphyrin units. Benefiting from the generated sub-1 nm channels for fast ion transport and the synergistic effect between evenly distributed PMo12 clusters and high-conductive CoTPyP units, the LIB based on the optimized PMo12/CoTPyP anode exhibits significantly improved Li+ storage capability as well as superior rate and cycling performance. The results of density functional theory simulations further reveal that the co-assembly of PMo12 and CoTPyP can accelerate the mobility of Li+ and electrons, which in turn promotes the enhancement of LIBs performance. This work paves a strategy for synthesizing POMs-based anode materials with simultaneously high dispersibility, redox activity, and stability.

2,5-Thiophenedicarboxylic Acid Bridging Hexameric CeIII-Substituted Selenotungstate and Its Application for Detecting Mucin 1

The development of polyoxometalate chemistry not only is derived from the continuous discovery of novel polyoxometalates (POMs) but also stems from the exploitation of their new functionalities. In this work, we obtained a rigid sulfur-containing heterocyclic ligand-linking aggregate [N(CH3)4]10Na6H6[Ce8(H2O)26W8(HTDA)2(TDA)2O20][SeW4O18]2[SeW9O33]4·112H2O (1) (H2TDA = 2,5-thiophenedicarboxylic acid). Its polyanionic unit consists of one [Ce4(H2O)13W4O10(HTDA)(TDA)O10]18+ cluster and two kinds of Keggin-type [SeW4O18] and [SeW9O33] segments. It is noteworthy that H2TDA ligands not only work as connectors to link two symmetrical {[Ce4(H2O)13W4(HTDA)(TDA)O10][SeW4O18][SeW9O33]2}11- units but also function as ornaments to graft to the polyanionic backbone. Furthermore, 1 and 3,4-ethylenedioxythiophene (EDOT) were deposited on the glassy carbon electrode (GCE) by the electropolymerization (EPM) method, resulting in a 1-poly(3,4-ethylenedioxythiophene) (1-PEDOT) composite film, which can provide sufficient binding sites to immobilize Au nanoparticles (Au NPs). Hereafter, the Au NPs-immobilized 1-PEDOT modified electrode (Au/1-PEDOT/GCE) was used to construct an electrochemical aptasensor to detect mucin 1, showing a low detection limit of 29.5 fM in the Tris solution. This work not only demonstrates that rigid heterocyclic ligands are beneficial for the creation of novel rare-earth-substituted selenotungstate hybrids but also provides more enlightenment for POM-based materials used for electrochemical detection of cancer markers.

Al8 Cluster-Based Metal Halide Frameworks: Balancing Singlet-Triplet Excited States to Achieve White Light and Multicolor Luminescence

Luminescent metal clusters have attracted great interest in current research; however, the design synthesis of Al clusters with color-tunable luminescence remains challenging. Herein, an [Al8 (OH)8 (NA)16 ] (Al8 , HNA = nicotinic acid) molecular cluster with dual luminescence properties of fluorescence and room-temperature phosphorescence (RTP) is synthesized by choosing HNA ligand as phosphor. Its prompt photoluminescence (PL) spectrum exhibits approximately white light emission at room temperature. Considering that halogen atoms can be used to regulate the RTP property by balancing the singlet and triplet excitons, different CdX2 (X- = Cl- , Br- , I- ) are introduced into the reactive system of the Al8 cluster, and three new Al8 cluster-based metal-organic frameworks, {[Al8 Cd3 Cl5 (OH)8 (NA)17 H2 O]·2HNA}n (CdCl2 -Al8 ), {[Al8 Cd4 Br7 (OH)8 (NA)16 CH3 CN]·NA·HNA}n (CdBr2 -Al8 ) and {[Al8 Cd8 I16 (OH)8 (NA)16 ]}n (CdI2 -Al8 ) are successfully obtained. They realize the color tunability from blue to yellow at room temperature. The origination of fluorescence and phosphorescence has also been illustrated by structure-property analysis and theoretical calculation. This work provides new insights into the design of multicolor luminescent metal cluster-based materials and develops advanced photo-functional materials for multicolor display, anti-counterfeiting, and encryption applications.

Small luminescent silver clusters stabilized in porous crystalline solids

Subnanometric or small metal clusters (SMCs) have been extensively researched due to their unique electronic, optical, catalytic, and magnetic properties, which differ from those of bulk samples. Among the SMCs, silver (Ag) clusters have received significant interest due to their affordability and unique luminescent properties. Currently, two major approaches, gas-phase and liquid-phase synthesis, have been employed to obtain Ag clusters with precise control of size and structure. More recently, attention has been directed toward the utilization of porous crystalline solids such as metal-organic frameworks (MOFs), zeolites, and porous ionic crystals (PICs) to synthesize and stabilize Ag clusters. In this review, we aim to provide a comprehensive overview of the synthesis, structures, and luminescent properties of Ag clusters in porous crystalline solids.

Ce-mediated molecular tailoring on gigantic polyoxometalate {Mo132} into half-closed {Ce11Mo96} for high proton conduction

Precise synthesis of polyoxometalates (POMs) is important for the fundamental understanding of the relationship between the structure and function of each building motif. However, it is a great challenge to realize the atomic-level tailoring of specific sites in POMs without altering the major framework. Herein, we report the case of Ce-mediated molecular tailoring on gigantic {Mo132}, which has a closed structural motif involving a never seen {Mo110} decamer. Such capped wheel {Mo132} undergoes a quasi-isomerism with known {Mo132} ball displaying different optical behaviors. Experiencing an 'Inner-On-Outer' binding process with the substituent of {Mo2} reactive sites in {Mo132}, the site-specific Ce ions drive the dissociation of {Mo2*} clipping sites and finally give rise to a predictable half-closed product {Ce11Mo96}. By virtue of the tailor-made open cavity, the {Ce11Mo96} achieves high proton conduction, nearly two orders of magnitude than that of {Mo132}. This work offers a significant step toward the controllable assembly of POM clusters through a Ce-mediated molecular tailoring process for desirable properties.