High-Nuclear Co-Added Polyoxometalate-Based Chain: Electrocatalytic Oxygen Production

A high-nuclear Co-added polyoxometalate (CoAP) was synthesized via a hydrothermal reaction: H14.5K9Na7.5-{[Co8(μ2-OH)(μ3-OH)2(H2O)2(Co(H2O)GeW6O26)(B-α-GeW9O34)2][BO(OH)2][Co12(μ2-OH)(μ3-OH)5(H2O)3(Co(H2O)GeW6O26)(GeW6O26)(B-α-GeW9O34)]}·46H2O (1). The polyoxoanion of 1 contains a large Co20 cluster gathered by lacunary GeW6O26 and GeW9O34 subunits. 1 represents a one-dimensional (1D) chain formed by adjacent polyoxoanions coupling through a CoO6 double bridge, showing the first example of a high-nuclear CoAP-based inorganic chain. 1 served as an efficient electrocatalyst in oxygen evolution reactions (OERs).

Research on the Construction of a Series of Transition Metal-Substituted Keggin-Type TMSPOMs@PCN-224 Composites through the Encapsulation Method and Their Electron Transfer Mechanism in CO2RR

In order to take advantage of the distinct reversible multielectron transfer properties of polyoxometalates (POMs) and increase the electron density at the active sites during the electrochemical reduction of CO2 (CO2RR), a range of transition metal-doped polyoxometalates (TMSPOMs) was entrapped within the porphyrin-based framework of PCN-224 via an encapsulation method, known as TMSPOMs@PCN-224 (TMSPOMs = [XW11O39MII(H2O)]n-, [XW11O40VIV]n-, M = CoII, MnII; X = Si, n = 6; X = P, n = 5). The central elements (Si, P) and the incorporated transition metals (VIV, CoII, and MnII) both play a role in adjusting the electronic structure and electron transfer during the CO2RR process. Remarkably, the composite material with cobalt substitution displayed significantly improved performance. Through fine-tuning the POM loading, the electrocatalytic activity was optimized, leading to an impressive Faradaic efficiency for CO production (FECO) of 89.9% for SiW11Co@PCN-224, a significant improvement compared to the 12.1% FECO of PCN-224. Furthermore, the electrochemical stability of this catalyst was demonstrated over 20 h. Comparative analyses involving six composite materials indicated a relationship between the negative charge of the polyanions and their ability to facilitate effective electron transfer, ultimately enhancing the catalyst's performance. Meanwhile, these findings were supported by density functional theory (DFT) calculations.

Designed Syntheses of Three {Ni6PW9}-Based Polyoxometalates, from Isolated Cluster to Cluster-Organic Helical Chain

Three new hexa-Ni-substituted Keggin-type polyoxometalates (POMs), [Ni6(OH)3- (DACH)3(H2O)6(PW9O34)]·31H2O (1), [Ni(DACH)2][Ni6(OH)3(DACH)3(HMIP)2(H2O)2(PW9O34)]·56 H2O (2), and [Ni(DACH)2][Ni6(OH)3(DACH)2(AP)(H2O)5(PW9O34)]·2H2O (3) (DACH = 1,2-Diami- nocyclohexane, MIP = 5-Methylisophthalate, AP = Adipate) were successfully made in the presence of DACH under hydrothermal conditions. 1 is an isolated hexa-Ni-substituted Keggin unit decorated by DACH. In order to further construct POM cluster-organic frameworks (POMCOFs) on the basis of 1, by analyzing the steric hindrances and orientations of the POM units, the rigid HMIP and flexible AP ligands were successively incorporated, and another anionic monomeric POM 2 and the new 1D POM cluster organic chain (POMCOC) 3 were obtained. HMIP ligand still acts as a decorating group on the Ni6 core of 2 but results in the different spatial arrangement of the {Ni6PW9} units. AP ligands in 3 successfully bridge adjacent isolated POM cluster units to 1D POMCOC with left-hand helices. The AP in 3 is the longest aliphatic carboxylic acid ligand in POMs, and the 1D POM cluster-AP helical chain represents the first 1D POMCOC with a helical feature.

Chiral {Ni6PW9} Cluster-Organic Framework: Synthesis, Structure, and Properties

A chiral three-dimensional polyoxometalate cluster-organic framework (POMCOF) H₃[(btc)Ni₆(μ₃-OH)₃(H₂O)₅(B-α-PW₉O₃₄)]·17H₂O (1, btc = 1,2,4-benzenetricarboxylate) has been made under hydrothermal conditions in the absence of amine or chiral starting reagents. 1 shows high stability in CH₃CN/DMF (1:3), acidic, and basic solutions with the pH ranging from 2 to 12 for 5 days. The UV-vis reflectance spectra and Mott-Schottky measurements reveal that 1 could be a suitable catalyst for photocatalysis. Visible-light-driven H₂ evolution studies have demonstrated that 1 is an ecofriendly, efficient, and recyclable catalyst with a H₂ evolution rate of 1058.24 μmol h^-1g^-1. Nonlinear optical (NLO) measurement reveals that 1 exhibits a second-harmonic generation (SHG) response of about 1.4 times that of KH₂PO₄ (KDP), indicating that 1 is a potential NLO material as well.

Three new POM-based coordination polymers with 1,3,5-tris(1-imidazolyl)benzene ligand: syntheses, structures and proton conductivity

Three POM-based coordination polymers with 1,3,5-tris(1-imidazolyl)benzene have been synthesized. 1 exhibits a rare 3,6-connected pyr topology; 2 and 3 reveal 3D hydrogen-bonded structures with good proton conductivity.

Syntheses, structures and properties of three organic–inorganic hybrid polyoxotungstates constructed from {Ni6PW9} building blocks: from isolated clusters to 2-D layers

Three organic–inorganic hybrid POMs were prepared and characterized, exhibiting 0-D to 2-D assemblies made by {Ni₆PW₉} SBUs and organic ligands.

Steam-assisted assemblies of {Ni6PW9}-based inorganic–organic hybrid chains: synthesis, crystal structures and properties

Three hexa-Ni-substituted Keggin phosphotungstate chains have been obtained through the SAC method, where H₂N-bdc and unprecedented {(Ni₆PW₉)PW₁₂} is reported for the first time.

A robust polyoxometalate-templated four-fold interpenetrating metal–organic framework showing efficient organic dye photodegradation in various pH aqueous solutions

A polyoxometalate-templated four-fold interpenetrating 3-D MOF of 1 acts as a photocatalyst, which can efficiently degrade the organic dyes under UV-Vis light irradiation in aqueous solutions over a wide pH range.

Hybrid dimers based on metal-substituted Keggin polyoxometalates (metal = Ti, Ln) for cyanosilylation catalysis

Six hybrid dimers 1–6 constructed from [PW₁₀Ti₂O₄₀]⁷⁻/[PW₁₁LnO₃₉]⁴⁻ and lanthanide–organic units are reported, which as heterogeneous catalysts show high activity for cyanosilylation under solvent-free conditions.

Influence of pendant 2-[1,2,4]triazol-4-yl-ethylamine and symmetrical bis(pyrazol) ligands on dimensional extension of POM-based compounds

By using pendant tea and bis(pyrazole) ligands H₂bdpm and H₂bhpe, five new Mo₈-based compounds have been synthesized. The tea induces low dimensional subunits of 1–3, while the H₂bdpm and H₂bhpe ligands induce high dimensional structures of 4 and 5.

A series of organic–inorganic hybrid materials consisting of flexible organic amine modified polyoxomolybdates: synthesis, structures and properties

A series of hybrid materials consisting of Tris[(2-pyridyl)methyl]amine modified polyoxomolybdates were obtained and some complexes have efficient photocatalytic activities to degrade pararosaniline hydrochloride dye molecules.

Architectural chemistry of polyoxometalate-based coordination frameworks constructed from flexible N-donor ligands

Polyoxometalate-based coordination frameworks (POMCFs) constructed from flexible N-donor ligands can exhibit diverse properties and fascinating architectures, extending the families of material chemistry and structural chemistry.

Organic–inorganic hybrid assemblies based on Ti-substituted polyoxometalates for photocatalytic dye degradation

New organic–inorganic hybrid compounds based on Ti-substituted polyoxometalates exhibit high photocatalytic dye (MB) degradation activities.

Polyoxometalate-directed assembly of various multinuclear metal–organic complexes with 4-amino-1,2,4-triazole and selective photocatalysis for organic dye degradation

Five POM-based metal–organic complexes ranging from 0D trinuclear cluster, 1D chain, 2D network, to 3D framework have been successfully prepared in the presence/absence of citric or boric acid.