POM-based Hybrid Research Articles

In Situ Ligand-Transformation-Assisted Assembly of a Polyoxometalate and Silver-Phosphine Oxide Cluster for Colorimetric Detection of Phenol Contaminants.

In situ ligand transformation strategies represent an efficient pathway for constructing function-oriented polyoxometalate (POM)-based crystalline materials. Herein, three POM-based hybrid networks were synthesized through in situ transformation of the phosphine ligand, formulated as [Ag(dppeo)6][H2PMo12O40]·5H2O (1), [Ag(dedpo)]4[SiW12O40]·6H2O (2), and [Ag(dppeo)]3[PW12O40]·3H2O (3) (dedpo = (2-(diphenylphosphaneyl)ethyl)diphenylphosphine oxide; dppeo = ethane-1,2-diylbis(diphenylphosphine oxide)). During the synthesis of these compounds, the 1,2-diphenylphosphine ethane molecule underwent in situ oxidation, transforming into dppeo and dedpo ligands, respectively. Compound 1 features a supramolecular architecture assembled from [Ag(dppeo)3]+/[Ag2(dppeo)6]2+ cationic clusters with disordered Ag centers and protonated [H2PMo12O40]- anions. Compound 2 presents a 3-D POM-supported metal-organic framework consisting of binuclear [Ag(dedpo)]22+ units, {-dedpo-Ag-dedpo-} chains, and [SiW12O40]4- polyoxoanions. Compound 3 displays a 2-D layered structure formed by {-dppeo-Ag3-dppeo-} chains and [PW12O40]3- clusters. Pronounced argentophilic interactions are observed in compounds 1 and 3. The three compounds demonstrate satisfactory heterogeneous catalytic activity in the colorimetric detection reactions toward phenol pollutants with detection limits of 1.73, 1.92, and 4.6 μM, respectively. Additionally, compounds 1-3 show high anti-interference capabilities and high sensitivity in differentiating phenol from its halogenated derivatives. This work presents some guidance for designing specific function-oriented POM-based materials via an in situ ligand transformation strategy.

Synthesis, structural characterization, electrochemical, photophysical and DNA binding properties of two Anderson POM-based hybrids

In this article, two new hybrid compounds Na(C2H7N4O)2[AlMo6(OH)6O18]·2H2O (DA) and (C4H13N5)[HAlMo6(OH)6O18].10H2O (MA) were obtained from the reaction of the organic ligands (dicyandiamide and metformin) with Anderson polyoxometalate (POM) in the water solution. Anderson POM based hybrids DA and MA were characterized by the spectroscopic methods such as, FTIR, UV–vis, photoluminescence. Crystal structures of the hybrid compounds were determined by single crystal X-ray diffraction studies. In the crystal structure of MA, Anderson type polyoxometalate anions are linked by OH·····O and NH·····O hydrogen bonds forming 2D supramolecular structure in which there are solvent accessible voids. In the structure of DA, type polyoxometalate anions are connected by Na+ ions forming 2D coordination polymer type structure. The electrochemical properties of the Anderson POM and its hybrids DA and MA were investigated in the range of -2 — (+2) V, range. It is seen that Anderson type POM has two oxidation and reduction potentials. These redox processes are reversible at the 0.3 and -0.75 V (Ipa/Ipc). On the other hand, the oxidation and reduction processes of the Anderson POM based hybrids DA and MA have shifted to the lower regions and all processes are irreversible process in this potential range. Thermal properties of the hybrids DA and MA were investigated in the 20—800 °C temperature range. UV–Vis spectral and viscosity measurements revealed that hybrids DA and MA interact with DNA via groove mode.

Development of a chromatographic method for optimizing the thiol-maleimide coupling of polyoxometalate-polymer hybrids

The covalent attachment of polyoxometalates (POMs) to polymers has been developed as a strategic approach for the advancement of POM-based hybrid materials with versatile applications. In this study, we utilized thiol-maleimide Michael addition to investigate the kinetics and efficacy of the “one-to-one” conjugation between Keggin type POM and polystyrene. We explored the effects of solvent polarity, catalyst, molecular weight of PS and synthetic strategies on the reaction kinetics and efficiency, by means of reverse-phase high-performance liquid chromatography (RP-HPLC). A series of comparative analysis affirmed the superior efficiency of the one-pot method, particularly when facilitated by the addition of a high-polarity solvent and an excess of maleimide. These findings offer valuable insights into the intricate interplay between reaction conditions, kinetics, and selectivity in thiol-maleimide reactions of POMs and polymers. They hold profound implications for advancing the study of POM-based multifunctional materials and the synthesis of complex hybrid molecules.

Copper-containing POM-based hybrid P2Mo22V4Cu4 nanocluster as heterogeneous catalyst for the light-driven hydroxylation of benzene to phenol.

The current traditional phenol production process has many shortcomings, and the efficient and clean photocatalytic one-step oxidation to phenol is gradually attracting attention. Heteropolyacids (PMo10V2) with high-density Lewis acid active sites and excellent photoelectron transfer ability are ideal choices for catalytic reactions. In this study, a copper-modified isolated dimeric hybrid nanocluster, [Cu(pyim)2]2[Cu(pyim)2(P2MoVI20MoV2VIV4O82)]2·(H2O) (pyim = [2-(pyridin-2-yl)imidazole]), was synthesized by a convenient hydrothermal method. The structural analysis demonstrated that the compound was composed of metal-organic complexes containing pyim ligands, Keggin-type heteropolyacids, and transition metal copper ions. Remarkably, this not only solves the difficulty that the heteropolymeric acid cannot be recovered by dissolving in the solvent but also introduces the copper atom as a second active center. The catalyst exhibited a benzene conversion of 15.6% and a selectivity of 85.2% in a mixed solution of acetonitrile and acetic acid under optimal reaction conditions. After four catalytic cycles, the PXRD pattern proved that the catalyst was still stable. This study provides a good idea for photocatalytic reactions and other environmental applications.

An iron-containing POM-based hybrid compound as a heterogeneous catalyst for one-step hydroxylation of benzene to phenol.

It is a major challenge to perform one-pot hydroxylation of benzene to phenol under mild conditions, which replaces the environmentally harmful cumene method. Thus, finding highly efficient heterogeneous catalysts that can be recycled is extremely significant. Herein, a (POM)-based hybrid compound {[FeII(pyim)2(C2H5O)][FeII(pyim)2(H2O)][PMoV2MoVI9VIV3O42]}·H2O (pyim = 2-(2-pyridyl)benzimidazole) (Fe2-PMo11V3) was successfully prepared by hydrothermal synthesis using typical Keggin POMs, iron ions and pyim ligands. Single-crystal diffraction shows that the Fe-pyim unit in Fe2-PMo11V3 forms a stable double-supported skeleton by Fe-O bonding to the polyacid anion. Remarkably, due to the introduction of vanadium, Fe2-PMo11V3 forms a divanadium-capped conformation. Benzene oxidation experiments indicated that Fe2-PMo11V3 can catalyze the benzene hydroxylation reaction to phenol in a mixed solution of acetonitrile and acetic acid containing H2O2 at 60 °C, affording a phenol yield of about 16.2% and a selectivity of about 94%.

Accordion-like polyoxometalate hybrid architectures for capacity-dense and flexible Zn-Ion battery cathodes

Polyoxometalates (POMs) have received significant attention as functional materials owing to their tunable structures and sizes, versatile electronic properties, and multiple electrochemical redox behaviours. However, the hierarchical architecture of POMs and their unique Zn storage mechanism have yet to be explored for Zn-ion battery (ZIB) applications. Herein, we demonstrate an accordion-like hierarchical architecture of POM-based hybrids (L-rGO/PPy@POM) via a redox-relay Heck reaction, where multi-layered reduced graphene oxide (rGO)/polypyrrole (PPy) hybrid nanosheets are assembled with ultrafine POM nanoparticles through specific interaction. As confirmed through in situ and ex situ spectroscopic methods, the Mo=O bond is more implicated in Zn2+ insertion than the two Mo–O single bonds and two edge-sharing and corner-sharing Mo–Mo bonds. Owing to a fast and facile redox kinetics, the ZIB cells with l-rGO/PPy@POM delivered high specific capacity of 269.3 mAh g−1 at 100 mA g−1, high-rate capacity of 68.0 mAh g−1 at 10,000 mA g−1, and 80.4% of capacity retention over 22,000 cycles in water-in-bisalt electrolytes. Furthermore, flexible quasi-solid-state ZIB full cells with l-rGO/PPy@POM cathode achieved the maximum volumetric energy and power densities of 51.1 mWh cmcell−3 and 1159.9 mW cmcell−3, demonstrating long-term cyclic stability and functional operation of various electronic devices.

A Calix[4]resorcinarene-Copper(II) Based Supramolecular Nanocapsule with Encapsulated Polyoxometalates for Enhanced Photocatalytic Activity

The research on improving the photocatalytic activity of polyoxometalates (POMs) has attracted considerable attention. In this work, a functionalized calix[4]resorcinarene ligand with four terpyridine groups (TPYR4A) was rationally designed, and then a POM-calix[4]resorcinarene based inorganic–organic complex [Cu4Cl4(TPYR4A)]2[PWVI10WV2O40][PWVI12O40]·6DMA·8H2O (DMA= N,N′-dimethylacetamide) (1) was achieved by a self-assembly process. Strikingly, POM clusters were successfully encapsulated in noncovalent dimeric calix[4]resorcinarene-copper(II) based nanocapsules with a size of 3 nm. Markedly, 1 features a visible light absorption response with an optical band gap of 2.3 eV. More importantly, 1 exhibits obviously enhanced photocatalytic activity for oxidation of benzaldehyde upon simulated solar light excitation. Particularly, the photocatalytic performance of 1 is better than that of pure H3PW12O40 or a mixture of TPYR4A and H3PW12O40. This work offers a feasible strategy for designing POM-based hybrid materials with enhanced photocatalytic activity.

Synthesis and Structural Elucidation of Pom-based Hybrid with a Common Cobalt Centre: It’s Antibacterial Activity and Future Perspectives

A novel hybrid Keggin tungstocobaltate [Co(H2O)6][C5H6N] H4[CoW12O40][NO3].3H2O was prepared by the hydrothermal method and was characterized by elemental analyses, IR spectra, TG-DTA and single crystal X-ray diffraction techniques. This might be the first example of transition metal fuctionalised POM where the same cobalt metal resides at the centre of both of the cationic and anionic complexes. Furthermore, their antibacterial efficacy was determined by MIC and MBC on Gram-negative (Escherichia coli, Salmonella typhi) and Gram-positive (Streptococcus pneumoniae, Bacillus cereus) bacteria. The results indicated an acceptable bacteriostatic and bactericidal effects of this hybrid polyoxometalate.

Dynamic co-assembly behaviors of polyoxometalates and giant surfactants in dual solvents

Inorganic-organic hybridization is a widely used method to develop new functional materials involving polyoxometalates (POMs), affording them with unique synergistic physical and chemical properties. As one of the core topics in hybrid materials, the study of their assembly structures is critical for the optimization of their performances.In the present work, dynamic co-assembly behaviors of several giant surfactants XPOSS-PS (X, POSS and PS denote different polar groups, polyhedral oligomeric silsesquioxane and polystyrene, respectively) and Keggin-type silicotungstic acid H4SiW12O40 (H4SiW for short) were investigated. We designed and synthesized three series of giant surfactants that possess heads bearing cationic (NPOSS-PS, N for ammonium group), neutral (DPOSS-PS, D for dihydroxyl group) and anionic charges (APOSS-PS, A for carboxylic acid group), respectively. The different charge types of POSS heads lead to different electrostatic interactions with the anionic POM clusters, resulting in different co-assembly structures in dual mixed solvents. Moreover, we found the POM's loading content and PS chain length are another two important factors that can determine the morphology of co-assembly structures. This work expands the scope of co-assembled structures of POM-based hybrid materials, and provides a platform for the study of the basic physical principles of their co-assembly behaviors.

Insights into the Structure of Keggin-Type Polyoxometalate-Based Organic-Inorganic Hybrid Materials: The Actual Ratio of Organic Cations to Heteropolyanions.

Polyoxometalate (POM)-based organic-inorganic hybrid materials possess versatile properties and applications; however, the ratios of organic cations to POM anions still remain to be solved. In this work, 14 POM-based organic-inorganic hybrid materials were synthesized by the precipitation, hydrothermal, and solvent-evaporation methods. These hybrid materials consisted of a wide range of quaternary ammonium and imidazolium cations with different alkyl chains and different Keggin-type heteropolyanions [i.e., phosphotungstic ([PW12O40]3-), phosphomolybdic ([PMo12O40]3-), silicotungstic ([SiW12O40]4-), and silicomolybdic ([SiMo12O40]4-) anions]. Their compositions and structures were characterized complementarily by elemental analysis, powder X-ray diffraction, single-crystal X-ray diffraction, and Fourier transform infrared spectroscopy. The actual ratios of organic cations to heteropolyanions of [PW12O40]3-, [PMo12O40]3-, [SiW12O40]4-, and [SiMo12O40]4- were found to always be 3:1, 3:1, 4:1, and 4:1, respectively, independent of the organic cations, synthesis methods, and reaction parameters. This finding demonstrates that the organic cations completely substituted the protons of the heteropolyacid precursors in the hybrid materials, which thus hardly possessed Brønsted acidity probed by the pyridine adsorption and cellulose hydrolysis reaction. Such complete substitution of the protons arose apparently from the strong noncovalent interactions between the organic cations and heteropolyanions (such as electrostatic and C-H···O interactions) in the POM-based hybrid materials.

Geometry-Modulated Self-Assembly Structures of Covalent Polyoxometalate–Polymer Hybrid in Bulk and Thin-Film States

This work reports the synthesis, characterization, and self-assembled structures of three series of Keggin-type polyoxometalate (POM)-based hybrid molecules KPOM-mPSn (m = 1, 2 and 3), in which one, two, or three polystyrene (PS) chains are covalently attached to a POM head, respectively. The classical “click” reaction was applied to prepare samples with predesigned molecular geometry, which were further purified by C18 reversed-phase high-performance liquid chromatography (RP-HPLC). Strong chemical incompatibility between inorganic POMs and organic PS chains drives the hybrid molecules to microphase separate into versatile nanostructures in both bulk and thin-film states. In thermally annealed bulk samples, four phase morphologies were found depending on both the overall molecular geometry and the volume fractions of PS tails, including lamellae (LAM), hexagonal packed cylinders (HEX), disordered micelles (DM), and body-centered cubic (BCC) packed spheres, as revealed by small-angle X-ray scattering (SAXS). In the thin-film state, LAM, HEX, and BCC structures were observed and proved by transmission electron microscopy (TEM) images and grazing incidence SAXS (GISAXS). This work expands the scope of self-assembled nanostructures of POM-based hybrid materials to spherical phases and provides a platform for the study of the basic physical principles of their self-assembly behavior.

Polyoxometalates in Extraction and Sorption Processes

ABSTRACT Polyoxometalates (POMs) represent a fascinating class of inorganic cluster compounds. Due to the almost unlimited possibilities to tailor size, shape and charge of this compound class and to perform various surface functionalization, they are discussed for different applications, especially in the fields of catalysis, material sciences, and biomedicine. In contrast, the systematic study of extraction and sorption properties of POMs has received relatively little attention so far. This review article provides a brief overview of relevant POM structures used for effective and selective phase transfer of metal ions from aqueous into organic media as well as for the development of efficient sorption processes. The use of inorganic-organic POM-based hybrid materials for extraction and sorption processes is also discussed.

Two Polyoxometalate-Based Hybrid Compounds Modified by Iron Schiff Base Complexes: Syntheses, Crystal structures, Cyclic Voltametric Studies and Nonlinear Optical Properties.

Two new polyoxometalate (POM)-based hybrid compounds modified by a Schiff base, [Fe(DAPSC)(H2 O)2 ]2 [HPMo2 V Mo10 VI O40 ] ⋅ 5H2 O (1) and [Fe(DAPSC)(H2 O)]2 [HPV3 IV Mo4 V Mo7 VI O42 ] ⋅ 6H2 O (2), (DAPSC=2,6-diacetylpyridine bis-(semicarbazone)), have been successfully constructed from typical Keggin POMs, iron ions, and DAPSC ligands under hydrothermal condition. Structural analysis demonstrates that the Fe-Schiff base ligand units are free from polyacid anions in compound 1. While in compound 2, the Fe-Schiff base ligand units are bridged with polyacid anions via Fe-O bonds to emerge a stable double-supported skeleton. Noticeably, owing to the introduction of vanadium in H5 PMo10 V2 O40 ⋅ 32.5H2 O, a divanadium-capped configuration is shaped in compound 2. Besides, the third-order nonlinear optical (NLO) properties of two compounds were explored. It should be noted that both compounds 1 and 2 have two-photon absorption properties, which indicates that the two compounds are potential nonlinear optical materials.

Assembly and luminescent property of a new polyoxometalate-based hybrid compound showing entangled double helical and porous motifs

A new polyoxometalate (POM)-based compound, (H3O)2[CuII3(btb)6][H4W12O40]2∙2H2O (btb = 1,4-bis(1,2,4-triazol-1-yl)butane) was hydrothermally synthesized, and characterized by elemental analyses, FT-IR spectrum, thermogravimetry analysis, powder X-Ray diffraction and single X-ray diffraction. Compound 1 is an unusual example of POM-based hybrid that consists of both helical and porous structural features. Moreover, luminescent property of compound 1 is investigated in the solid state at room temperature. In contrast to free btpe ligand, compound 1 exhibits an enhanced luminescent property, attributed to an internal heavy metal effect.

Hydrothermal assembly, structural diversity, and photocatalytic characterization of two polyoxometalates-based hybrid CuII and CuI coordination polymers with 2,6-(1,2,4-triazole-4-yl)pyridine

In this work, under hydrothermal conditions, two novel polyoxometalates (POMs)-based CuII and CuI hybrid materials with 2,6-(1,2,4-triazole-4-yl)pyridine (L1), namely yellow block crystals [Cu2(L1)2(Mo4O13)] (1) and blue block crystals [Cu2(L1)3(H2O)2(Mo4O13)2] (2) have been designed and synthesized. These POM-based CuII and CuI hybrid materials 1–2 have been determined by single crystal X-ray diffraction analyses. In 1, these Mo8O26 4− anions and CuI centers are inter-linked by bidentate L1, which are arranged into the 1 D POMs-based CuI hybrid metal-organic framework. In 2, these L1 ligands bridge neighboring CuII centers and Mo8O26 4− anions, which ultimately form the unique 3 D POM-based CuII hybrid coordination framework of 2. Photocatalytic activities for decomposition of different organic dyes (Rhodamine B (RhB), methylene blue (MB) and methyl orange (MO)) have been investigated for 2, indicating that 2 are good candidates for the photocatalytic degradation of these organic dyes.

Isomeric organic ligand dominating polyoxometalate-based hybrid compounds: synthesis and as electrocatalysts and pH-sensitive probes

By introducing isomeric organic ligands into polyoxometalate (POM) systems, two new POM-based hybrid compounds, [Cu6(m-pyttz)2(H2O)][HPMo12O40] (1) and [Ag3(p-H2pyttz)(p-Hpyttz)Cl][H2PMo12O40]·6H2O (2) (m-/p-H2pyttz = 3-(pyrid-3/4-yl)-5(1H-1,2,4-triazol-3-yl)-1,2,4-triazolyl), have been hydrothermally synthesized and characterized. Single-crystal structural analysis shows the m-pyttz ligands link CuI ions to generate a two-dimensional layer with hanger-like rhombus, which is pillared by the PMo12 anions in 1. Compound 2 exhibits a three-dimensional supramolecular framework, in which PMo12 anions are building blocks facilitating the extension of the whole structure. The influence of the coordination modes of m-/p-H2pyttz on the structures is discussed in detail. Furthermore, electrochemical properties of 1 and 2 have been studied and they display excellent electrocatalytic activities toward the reduction of nitrite and hydrogen peroxide and pH-dependent electrochemical behaviors.

Are Keggin's POMs Charged Nanocolloids or Multicharged Anions?

Owing to their multiple charges and their nanometric size, polyoxometalates (POMs) are at the frontier between ions and charged colloids. We investigated here the effect of POM-POM electrostatics repulsions on their self-diffusion in water by varying POM and supporting salt concentrations. The self-diffusion coefficients of two Keggin's POMs [silicotungstate (SiW12O404-) and phosphotungstate (PW12O403-)] were determined by dynamic light scattering (DLS) and 1H/31P DOSY NMR, whereas POM-POM electrostatic repulsions were investigated by the determination of the static structure factors using small-angle X-ray scattering (SAXS). The self-diffusion coefficients for the two POMs and for different POM/background salt concentrations were collected in a master curve by comparing the averaged POM-POM distance in solution to the Debye length. As for classical charged colloids, we show that the POM's counterions should not be considered in the calculation of the ionic strength that governs POM-POM electrostatic repulsions. This result was confirmed by fitting the POM-POM structure factor by considering a pair potential of spherical charged particles using the well-known Hayter mean spherical approximation (MSA). These Keggin POMs also behave as (super)chaotropic anions (i.e., they have a strong propensity to adsorb on (neutral polar) surfaces, which was also investigated) here on the surface of octyl-β-glucoside (C8G1) micelles. The variations of (i) the chemical shift of 1H/31P NMR signals and (ii) the self-diffusion coefficients obtained by DOSY 1H/31P NMR of PW3- and of C8G1 were in good agreement, confirming the strong adsorption of POMs on the micelle polar surface from static and dynamic points of view. We concluded that Keggin's POMs behave (i) as anions because they adsorb on surfaces as chaotropic anions and (ii) as colloids because they can be described by a classical colloidal approach by dynamic and static scattering techniques (i.e., by the investigation of their interparticle electrostatic structure factor and self-diffusion without considering the POM's counterions in the ionic strength calculation). This work highlights the dynamic properties of POMs at soft interfaces compared to bulk aqueous solution, which is essential in the understanding of functional properties of POMs, such as (photo)catalysis and the rational design of POM-based hybrid nanomaterials from soft templating routes (i.e., in aqueous solutions at room temperature).

The antibacterial activity of polyoxometalates: structures, antibiotic effects and future perspectives.

Polyoxometalates (POMs) are, mostly anionic, metal oxide compounds that span a wide range of tunable physical and chemical features rendering them very interesting for biological purposes, an continuously emerging but little explored field. Due to their biological and biochemical effects, including antitumor, -viral and -bacterial properties, POMs and POM-based systems are considered as promising future metallodrugs. In this article, we focus on the antibacterial activity of POMs and their therapeutic potential in the battle against bacteria and their increasing resistance against pharmaceuticals. Recent advances in the synthesis of POMs are highlighted, with emphasis on the development and properties of biologically active POM-based hybrid and nanocomposite structures. By analysing the antibacterial activity and structure of POMs, putative mode of actions are provided, including potential targets for POM-protein interactions, and a structure-activity-relationship was established for a series of POMs against two bacteria, namely Helicobacter pylori and Streptococcus pneumoniae.

Two New Preyssler-Type Polyoxometalate-Based Coordination Polymers and Their Application in Horseradish Peroxidase Immobilization.

Enzyme immobilization is of increasing importance for biocatalysis, for which good supports are critical. Herein, two new Preyssler-type polyoxometalate (POM)-based coordination polymers, namely, {[Cu(H2 biim)2 ][{Cu(H2 biim)2 (μ-H2 O)}2 Cu(H2 biim)(H2 O)2 ]H[({Cu(H2 biim)(H2 O)2 }0.5 )2 ((μ-C3 HN2 Cl2 ){Cu(H2 biim)}2 ){Z(H2 O)P5 W30 O110 }]⋅x H2 O}n (1: Z=Na, x=9; 2: Z=Ag, x=10; H2 biim=2,2'-biimidazole) were designed and synthesized. Compounds 1 and 2 exhibit the same skeletons, which contain multiple CuII complex fragments and penta-supported {ZP5 W30 } (Z=Na, Ag) clusters. They were first employed to immobilize horseradish peroxidase (HRP). Results show that compounds 1 and 2 are good supports for HRP immobilization, and exhibit higher enzyme loading, lower loading times, and excellent reusability. The immobilized HRP (HRP/1 or HRP/2) was further applied to detect H2 O2 , and good sensitivity, wide linear range, low detection limit, and fast response were achieved. This work shows that POM-based hybrid materials are a new kind of promising support for enzyme immobilization.

Two new Keggin-type polyoxometalate-based organic-inorganic hybrid compounds with metal ions and chelate ligands

Two new hybrid compounds with chemical formulas [Co(L1)2(H2O)2]2[SiW12O40]·6H2O (1) and [Cu2(C9H22 N)2(L2)2][SiW12O40]·2H2O (2) (L1 = 3,3′-diamino-5,5′-bis(1H-1,2,4-triazole), L2 = 1,2-bis(3-(2-pyridyl)pyrazole-1-ylmethyl)benzene, C9H22 N = tripropylamine) were prepared in a hydrothermal reaction system containing Keggin-type polyoxometalates (POMs), transition metal (TM) salts (cobalt salts and copper salts), and chelate L1/L2 ligands. X-ray structural analysis reveals that 1 and 2 possess 3-D supramolecular host frameworks with large cavities and the polyoxoanions SiW12 reside in these cavities as the guest templates. The photocatalytic activities of 1 and 2 were investigated. Both compounds show efficient catalytic activity for degradation of RhB with 1 > 2. The loading amount of the POM units and the structural features of these POM-based organic-inorganic hybrid compounds may be necessary factors that affect the activity of catalysts in the photocatalytic degradation.