Recent Progress on Functionalized Nanoporous Heteropoly Acids: From Synthesis to Applications

Functionalized nanoporous heteropoly acids (HPAs) have garnered significant attention in recent years due to their enhanced surface area and porosity, as well as their potential for low-cost regeneration compared to bulk materials. This review aims to provide an overview of the recent advancements in the synthesis and applications of functionalized HPAs. We begin by introducing the fundamental properties of HPAs and their unique structure, followed by a comprehensive overview of the various approaches employed for the synthesis of functionalized HPAs, including salts, anchoring onto supports, and implementing mesoporous silica sieves. The potential applications of functionalized HPAs in various fields are also discussed, highlighting their boosted performance in a wide range of applications. Finally, we address the current challenges and present future prospects in the development of functionalized HPAs, particularly in the context of mesoporous HPAs. This review aims to provide a comprehensive summary of the recent progress in the field, highlighting the significant advancements made in the synthesis and applications of functionalized HPAs.

A CsCl-type inorganic cluster-based high-symmetry crystal built from {Mo4.55V7.45PO40}10.45- with a high ratio of vanadium to molybdenum and {(H2O)0.3@K6(H2O)12}6+ clusters exhibiting proton conduction below the freezing point of water

As a class of anionic oxoclusters of early transition metals in their highest oxidation states, polyoxometalates (POMs) show considerable structural versatility and unique chemical and physical properties, making them promising multifunctional materials. In this study, a Keggin-type POM has been achieved, with a formula of [(H2O)0.3@K6(H2O)12]H4.45[PV7.45Mo4.55O40]·11H2O (1), and its microcrystals and nanocrystals have been obtained, respectively. This POM was characterized by elemental analysis for C, H and N, ICP-MS, TG, PXRD, SEM, X-band EPR and XPS techniques. Single crystal X-ray diffraction analysis demonstrated that 1 shows a rare extended structure with a high-connected three-dimensional (3D) all inorganic network of a Keggin-type POM, built from {Mo4.55V7.45PO40}10.45- polyoxoanions and {(H2O)0.3@K6(H2O)12}6+ clusters with CsCl-type crystal structure. In addition, to the best of our knowledge, 1 shows the highest ratio of vanadium to molybdenum among Keggin-type POMs reported thus far. Most interestingly, 1 exhibits intrinsic proton conduction below the freezing point of water, with a proton conductivity of 6.90 × 10-7 S cm-1 at 249 K and further reaching 3.36 × 10-6 S cm-1 at 272 K and Ea = 0.44 eV at 249-272 K.

A "directed precursor self-assembly" strategy for the facile synthesis of heteropoly blues: crystal structures, formation mechanism and electron distribution

Recent research studies demonstrated that heteropoly blues (reduced polyoxometalates) could act as a special kind of solid material with potential functions in antiviral activity, and photocatalytic, photothermal and semiconducting properties. In this work, we develop a "directed precursor self-assembly" strategy for the facile synthesis of heteropoly blues (HPBs), so four representative HPBs [GeW₁₀MoO₄₀], [GeMoMoO₄₀], [P₂W₁₆MoO₆₂] and [P₂W₁₂MoMoO₆₂] have been synthesized and structurally characterized. These four heteropoly blue compounds were synthesized by the solution self-assembly reaction of a precursor [MoO₄(H₂O)₂(ox)₂]^2- with vacant polyoxometalates. Electrospray ionization mass spectrometry (ESI-MS) was used to analyze the assembly mechanism of these HPBs. A detailed study on the magnetic properties was also carried out, which shows that the number of Mo^V and their locations are capable of adjusting the electron distribution in HPBs.

Polyoxometalates in dye-sensitized solar cells

Dye-sensitized solar cells (DSSCs) are the third generation of photovoltaic cells developed by Grätzel and O'Regan. They have the characteristics of low cost, simple manufacturing process, tunable optical properties, and higher photoelectric conversion efficiency (PCE). With an ever increasing energy crisis, there is an urgent need to develop highly efficient, environmentally benign, and energy-saving cell materials. Polyoxometalates (POMs), a kind of molecular inorganic quasi-semiconductor, are promising candidates for use in different parts of DSSCs due to their excellent photosensitivity, redox, and catalytic properties, as well as their relative stability. Following a brief introduction to the development of DSSCs and the potential virtues of POMs in DSSCs, we attempt to make some generalizations about the energy level regulation of POMs that is the underlying theoretical basis for their application in DSSCs, and then we summarize the research progress of POMs in DSSCs in recent years. This is organized in terms of the properties of POMs, namely, electron acceptor, photosensitivity, redox and catalysis, based on the accumulation of our research into POMs over many years. Meanwhile, in view of the fact that the properties of POMs depend primarily on their electronic structural diversity, we keep this point in mind throughout the article with a view to revealing their structure-property relationships. Finally we provide a short summary and remarks on the future outlook. This review may be of interest to synthetic chemists devoted to designing POMs with specific structures, and researchers engaged in the extension of POMs to photoelectric materials.

A new 3D POMOF with two channels consisting of Wells–Dawson arsenotungstate and {Cl4Cu10(pz)11} complexes: synthesis, crystal structure, and properties

A new 3D POMOF based on Wells–Dawson arsenotungstate was prepared using a hydrothermal reaction. The POMOF exhibits a novel topological structure, photoluminescence properties, and excellent photocatalytic activity.

Efficient and robust photocatalysts based on {P2W18} modified by an Ag complex

Ag⁺ and the flexible ligand bimb were introduced into Dawson phosphomolybdate systems as linkage units to induce two fascinating 3-D inorganic–organic networks, which exhibit excellent electro- and photo-catalytic behavior.

Evans–Showell-type polyoxometalate constructing novel 3D inorganic architectures with alkaline earth metal linkers: syntheses, structures and catalytic properties

Two 3D frameworks and two 2D networks with an excellent catalytic effect of cyanosilylation were successfully obtained, originating from Evans–Showell-type polyoxoanions [Co₂Mo₁₀H₄O₃₈]⁶⁻ and alkaline earth metal cations (Sr²⁺, Ba²⁺).

A novel 3D POMOF based on Wells–Dawson arsenomolybdates with excellent photocatalytic and lithium-ion battery performance

A novel 3D POMOF based on Wells–Dawson arsenomolybdates exhibits fluorescence property and efficient and stable photocatalytic activity for MB and RhB under UV irradiation and has also been evaluated as the anode material for LIBs.

Two unusual 3D honeycomb networks based on Wells–Dawson arsenomolybdates with d10 transition-metal-pyrazole connectors

Two unusual 3D honeycomb networks based on Wells–Dawson arsenomolybdates were first reported, which have highly efficient catalytic ability for the degradation of organic dyes under UV irradiation and obvious electrocatalytic activities for the reduction of H₂O₂.

A Series of Multifunctional Metal-Organic Frameworks Showing Excellent Luminescent Sensing, Sensitization, and Adsorbent Abilities

A series of highly luminescent-active metal-organic frameworks (MOFs) 1-3 with hierarchical pores have been rationally constructed and fully characterized. The predesigned semi-rigid hexacarboxylate ligand hexa[4-(carboxyphenyl)oxamethyl]-3-oxapentane acid (H6 L) has been adapted with various space-directed N donors (i.e., 2,2'-bipyridine, 4,4'-di(1H-imidazol-1-yl)-1,1'-biphenyl, and 1,3,5-tri(1H-imidazol-1-yl)benzene) from a bidentate V-shape to a tridentate Y-shape. This family of multifunctional MOF materials represents a variety of potential applications in the following aspects: first, as luminescent sensors that show a fast and sensitive detection for pollutant CrO4 (2-) and Cr2 O7 (2-) ions in aqueous media; second, as adsorbents that can rapidly remove harmful organic dyes; third, as an antenna that can effectively sensitize visible-light-emitting Tb(3+) ions. These multifunctional MOF materials combine optical-sensing, adsorption, and sensitization properties, thus are very useful in many potential applications. Furthermore, these materials have proved to be reusable.

Recent developments in heterogeneous photocatalytic water treatment using visible light-responsive photocatalysts: a review

This review summarizes the recent progress in the design, fabrication, and application of visible light-responsive photocatalysts.

Assembly of a basket-like {Sr ⊂ P6Mo18O73} cage from 0D dimmer to 2D network and its photo-/electro-catalytic properties

Five semiconductor materials based on basket-like POM have been hydrothermally synthesized, which show high-efficient degradation ability for organic dyes RhB, MB, and AP in short time and bifunctional electrocatalytic behavior for oxidation of AA and reduction of NO₂⁻.

Polyoxometalates-based heterometallic organic–inorganic hybrid materials for rapid adsorption and selective separation of methylene blue from aqueous solutions

A series of POMs-based hybrid materials exhibit rapid adsorption rate, high uptake capacity and excellent selective separation towards cationic dye.

High-efficiency photo- and electro-catalytic material based on a basket-like {Sr⊂P6Mo18O73} cage

The first 8-connected 2D layer based on basket-liked {Sr⊂P₆Mo₁₈O₇₃} cage was prepared, which exhibits high-efficient photodegradation ability for MB, RhB, and AP under visible and UV light, as well as bifunctional electrocatalytic behavior.