Assembly of three organic–inorganic hybrid supramolecular materials based on reduced molybdenum(V) phosphates

Two {CuI[P4Mo6]2}-Based Coordination Polymers Incorporating In Situ Converted Tetrapyridyl Ligands for Trace Analysis of Nitrofuran Antibiotics

Nitrofurans are important synthetic broad-spectrum antibacterial drugs with the basic structure of 5-nitrofuran. Due to their toxicity, it is essential to develop a sensitive sensor with strong anti-interference capabilities for their detection. In this work, two {P4Mo6O31}12--based compounds, [H4(HPTTP)]2{CuI[Mo12O24(OH)6(PO4)3(HPO4)(H2PO4)4]}·xH2O (x = 13 for (1), 7 for (2); HPTTP = 4,4',4″,4‴-(1H-pyrrole-2,3,4,5-tetrayl)tetrapyridine), exhibiting similar coordination but distinct stacking modes. Both compounds were synthesized and used for the electrochemical detection of nitrofuran antibiotics. The tetrapyridine-based ligand was generated in situ during assembly, and its potential mechanism was discussed. Composite electrode materials, formed by mixing graphite powder with compounds 1-2 and physically grinding them, proved to be highly effective in the electrochemical trace detection of furazolidone (FZD) and furaltadone hydrochloride (FTD·HCl) under optimal conditions. Besides, the possible electrochemical detection mechanisms of two nitro-antibiotics were studied.

Hourglass shaped polyoxometalate-based materials as electrochemical sensors for the detection of trace Cr(VI) in a wide pH range

Due to Chromium hexavalent Cr(VI) is one of the most carcinogenic toxic ions, it is essential for finding a low-cost, efficient and highly selective detection method. Considering the wide range of pH detection in water, a major issue is exploring high sensitive electrocatalyst. Thus, two crystalline materials with hourglass {P₄Mo₆} clusters in different metal centers were synthesized and had fabulous Cr(VI) detection performance in a wide pH range. At pH = 0, the sensitivities of CUST-572 and CUST-573 were 133.89 μA μM^-1 and 30.05 μA μM^-1, and the detection limits (LODs) of Cr(VI) were 26.81 nM and 50.63 nM which met World Health Organization (WHO) standard for drinking water. CUST-572 and CUST-573 also had good detection performance at pH = 1-4. In actual water samples, CUST-572 and CUST-573 also possessed sensitivities of 94.79 μA μM^-1 and 20.09 μA μM^-1 and LODs were 28.25 nM and 52.24 nM, showing high selectivity and chemical stability. The difference of the detection performance of CUST-572 and CUST-573 were mainly attributed to the interaction between {P₄Mo₆} and different metal centers of crystalline materials. In this work, electrochemical sensors for Cr(VI) detection in a wide pH range were explored, providing important guidance for the design of efficient electrochemical sensors for ultra-trace detection of heavy metal ions in practical environments.

Two three-dimensional polyanionic clusters [M(P4Mo6)2] (M = Co, Zn) exhibiting excellent photocatalytic CO2 reduction performance

Two captivating {P4Mo6}-based compounds, formulated as (H2bbi)2{[Co2(bbi)][Co2.33(H2O)4][H9.33CoP8Mo12O62]}·4H2O (1) and (H2bbi){[Zn(Hbbi)]2[Zn0.75(bbi)][K2Zn(H2O)4][H8.5ZnP8Mo12O62]} (2) [bbi = 1,1'-(1,4-butanediyl)bis(imidazole)], were successfully synthesized under hydrothermal conditions. Structural analysis demonstrates that compounds 1 and 2 are constructed from hourglass-shaped structures [M(P4Mo6O31)2]n- (M = Co, Zn), which are all made up of molybdophosphates and one transition metal ion as the central connecting node. Compounds 1 and 2 feature three-dimensional (3D) frameworks, which are all connected to form a 3D structure by metal ions and bbi ligands. More interestingly, compound 1 exhibits higher catalytic activity than 2 in CO2 photoreduction due to the suitable energy band structure of Co species in {P4Mo6} clusters. The CO yield was 3261 μmol g-1 with high selectivity in 8 h for compound 1 in photocatalytic CO2 reduction, which is highly promising in the photocatalytic field. Additionally, the photoluminescence properties of 2 were investigated.

Assembling [M(P4Mo6)2] (M = Na, Mn, Na/Cu) dimeric clusters via transition metal/sodium ions into 0D to 3D phosphomolybdates

Six novel molybdenum(v) phosphates with structures ranging from a zero-dimensional cluster to three-dimensional frameworks have been solvothermally synthesized.

Influence of Pb element on the catalytic properties of {P4Mo6}-polyoxometalate for redox reactions

To introduce Pb element into the crystal framework of a polyoxoanion, a series of hybrid compounds were synthesized and characterized: (H₂bpp)₅[PbMn(H₂O)₂]₂H₂{Mn[Mo₆O₁₂(OH)₃(HPO₄)₃(PO₄)]₂}₂·8H₂O (1), (H₂bpp)₃[PbM(H₂O)₂]₂H₆{M[Mo₆O₁₂(OH)₃(HPO₄)₃(PO₄)]₂}₂·6H₂O (M = Ni (2), Co (3)) and (H₂bpp)₃[PbCd(H₂O)₂]₂H₆{Cd[Mo₆O₁₂(OH)₃(HPO₄)₃(PO₄)]₂}₂·4H₂O (4) (bpp = 1,3-bis(4-pyridyl)propane). Crystal structures were determined and characterized by IR, TG, XPS and single-crystal X-ray diffraction. Hybrids 1-4 have similar compositions; the inorganic moiety has a high-dimensional polyanionic arrangement formed from bi-metallic {PbM} subunits covalently bridging negative {M(P₄Mo)₂} clusters; the organic moiety is made up of protonated bpp cations that surround anionic clusters through many complex supramolecular interactions. Experimental results showed that the introduction of Pb can modulate the electrochemical properties of crystal materials, leading to the more reversible redox process of {M(P₄Mo₆)₂}-based hybrids. Hybrids 1-4 were employed as heterogeneous catalysts for redox reactions to evaluate their activity involving the transfer of electrons. It was found that these kinds of hybrids were catalytically active in the reduction reaction of [Fe(CN)₆]^3- (+S₂O₃^2-) → [Fe(CN)₆]^4-, but were inactive for Cr(vi) (+HCOOH) → Cr(iii) at 25-70 °C. The effect of temperature on the catalytic ability of hybrids was studied, and it was found that 50 °C was the optimal reaction condition for the four compounds to catalyze [Fe(CN)₆]^3- → [Fe(CN)₆]^4-. The reduction percentages of Fe(iii) in 270 min were about 95.7% (1), 76.95% (2), 89.39% (3) and 80.8% (4). The well-defined polyanionic structure with tunable structural features might be beneficial for exploring the mechanism of catalytic redox reactions at the molecular level.

Novel fully reduced phosphomolybdates for highly efficient removal of inorganic hexavalent chromium and the organic dye methylene blue

New Na-bridged phosphomolybdates as heterogeneous catalysts exhibit efficient catalytic performance on the reduction of hexavalent chromium and photodegradation of methylene blue.

Transition Metal Titanophosphates with Intercalated Molecular Photoluminescence and Catalytic Properties

In this study, α-TiP layered structure incorporating a heterometal center for organic ligand binding to enhance structural complexity and functionality were prepared. The protons of the α-TiP layer were replaced with zinc ions coordinated by 4-pyridinecarboxylic acid (PCA) and water to form a layer structure, TiZn(PO₄ )₂ (H₂ O)(PCA) (1). The tetrahedral zinc center with coordinated water in 1 is unprecedented in zincophosphate or zinc-MOF systems and is usually only found in metalloenzyme systems. The neutral zincotitanophosphate layers, tightly stacked through hydrogen bonds, showed velcro-like behavior on intercalating 4,4'-trimethylenedipyridine (TMDP) reversibly. It rendered a remarkable luminescence property to 1, emitting blue-to-white light under UV excitation. Surprisingly, the replacement of TMDP for PCA in the hydrothermal synthesis still resulted in 1, plus another structure, Ti₄ Zn₂ (H₂ TPB)(PO₄ )₄ (HPO₄ )₄ (H₂ PO₄ )₂ (2) (TPB=1,2,4,5-tetra(4-pyridyl)benzene). Clearly, in situ C-C cracking and C-C coupling of TMDP simultaneously occurred to generate PCA and TPB and thereafter the oxidant, Zn(NO₃ )₂ , was quantitatively determined to isolate crystal 1 from 2. The structure of 2 also featured α-TiP layers with pedant Zn tetrahedra but formed a three-dimensional neutral framework through TPB. For the first time, α-TiP-derived structures and their properties have been elucidated, which help in understanding intriguing in situ ligand formation and intercalation-induced luminescence, to exploit potential photocatalysis in polymerization.

Models to predict the magnetic properties of single- and multiple-bridged phosphate CuII systems: a theoretical DFT insight

Models for the 1,1 and 1,3-bridging modes of phosphate for copper(ii) compounds were developed. Using unrestricted corresponding orbitals (UCO), a graphical identification of the predominant exchange pathway was described.

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.