Modular construction, magnetism and photocatalytic properties of two new metal-organic frameworks based on a semi-rigid tetracarboxylate ligand

Rational Design and Synthesis of Fe-Doped Co-Based Coordination Polymer Composite Photocatalysts for the Degradation of Norfloxacin and Ciprofloxacin

The solar light-responsive Fe-doped Co-based coordination polymer (Fe@Co-CP) photocatalyst was synthesized under mild conditions. [Co(4-padpe)(1,3-BDC)]n (Co-CP) was first constructed using mixed ligands through the hydrothermal method. Then, Fe was introduced into the Co-CP framework to achieve the enhanced photocatalytic activity. The optimal Fe@Co-CP-2 exhibited excellent catalytic degradation performance for norfloxacin and ciprofloxacin under sunlight irradiation without auxiliary oxidants, and the degradation rates were 91.25 and 92.66% in 120 min. These excellent photocatalytic properties were ascribed to the generation of the Fe-O bond, which not only enhanced the light absorption intensity but also accelerated the separation efficiency of electrons and holes, and hence significantly improved the photocatalytic property of the composites. Meanwhile, Fe@Co-CP-2 displayed excellent stability and reusability. In addition, the degradation pathways and intermediates of antibiotic molecules were effectively analyzed. The free radical scavenging experiment and ESR results confirmed that •OH, •O2-, and h+ active species were involved in the catalytic degradation reaction; the corresponding mechanisms were deeply investigated. This study provides a fresh approach for constructing Fe-doped Co-CP-based composite materials as photocatalysts for degradation of antibiotic contaminants.

Design and Solvothermal Synthesis of Polyoxometalate-Based Cu(II)-Pyrazolate Photocatalytic Compounds for Solar-Light-Driven Hydrogen Evolution

Polyoxometalates (POMs) are known for their photocatalytic hydrogen production activity, but their solubility and limited stability often restrict their practical applications. Herein, we designed and solvothermally synthesized two new Cu-H₂bpz (3,3',5,5'-tetramethyl-4,4'-bipyrazole, abbreviated as H₂bpz) compounds, namely, Cu_0.5(H₂bpz)(NO₃) (1) and Cu(Hbpz)(Cl)·DMF (2), and three new polyoxometalate-based Cu(II)-pyrazolate compounds, namely, Cu(PW₁₂O₄₀)_0.5(H₂bpz)₂(H₂O)·(OH)_0.5(H₂O)_5.5 (3), Cu(HPMo₁₂O₄₀)(H₂bpz)₂(H₂O)₂·(H₂O)₄ (4), and Cu₂(SiW₁₂O₄₀)(H₂bpz)₃(H₂O)₃·(H₂O)₆ (5). Compound 3 (Cu(PW₁₂O₄₀)_0.5(H₂bpz)₂(H₂O)·(OH)_0.5(H₂O)_5.5) exhibits the best photocatalytic activity of 44.4 μ L h^-1 g^-1, which may be related to the stability of compounds. Herein, the solvothermal method has been proven to be an effective method in synthesizing stable organic-inorganic hybrid compounds with soluble POMs, metal ions, and organic ligands. Thus, heterogeneous catalysts with outstanding solar-light-driven photocatalytic properties were obtained.

Four structural diversity MOF-photocatalysts readily prepared for the degradation of the methyl violet dye under UV-visible light

The photocatalytic results demonstrated that all of them displayed efficient photocatalytic performances towards the degradation of methyl violet. The mechanism has been proposed.

Tuning dimensionality between 2D and 1D MOFs by lanthanide contraction and ligand-to-metal ratio

2D/1D dimensionality tuning in LnMOFs is related to both (i) ligand-to-metal ratio and (ii) lanthanide contraction, this is only possible with Er/Tm, lighter lanthanides e.g. Pr only produced 2D MOFs, despite different ligand-to-metal ratios were used.

Homocoupling Reactions of Azoles and Their Applications in Coordination Chemistry

Pyrazole, a member of the structural class of azoles, exhibits molecular properties of interest in pharmaceuticals and materials chemistry, owing to the two adjacent nitrogen atoms in the five-membered ring system. The weakly basic nitrogen atoms of deprotonated pyrazoles have been applied in coordination chemistry, particularly to access coordination polymers and metal-organic frameworks, and homocoupling reactions can in principle provide facile access to bipyrazole ligands. In this context, we summarize recent advances in homocoupling reactions of pyrazoles and other types of azoles (imidazoles, triazoles and tetrazoles) to highlight the utility of homocoupling reactions in synthesizing symmetric bi-heteroaryl systems compared with traditional synthesis. Metal-free reactions and transition-metal catalyzed homocoupling reactions are discussed with reaction mechanisms in detail.

H-Bonded and metal(ii)-organic architectures assembled from an unexplored aromatic tricarboxylic acid: structural variety and functional properties

This study reports the application of an aromatic tricarboxylic acid, 2,5-di(4-carboxylphenyl)nicotinic acid (H3dcna) as a versatile and unexplored organic building block for assembling a new series of metal(ii) (M = Co, Ni, Zn, Fe, and Mn) complexes and coordination polymers, namely [M(Hdcna)(phen)2(H2O)]·H2O (M = Co (1), Ni (2)), [Zn(μ-Hdcna)(phen)]n (3), [Co(μ-Hdcna)(bipy)(H2O)2]n·nH2O (4), [Zn2(μ-Hdcna)2(bipy)2(H2O)4]·6H2O (5), [Zn(μ3-Hdcna)(H2biim)]n (6), [Ni2(Hdcna)2(μ-bpb)(bpb)2(H2O)4] (7), [Fe(μ4-Hdcna)(μ-H2O)]n·nH2O (8), and [Mn3(μ5-dcna)2(bipy)2(H2O)2]n·2nH2O (9). Such a diversity of products was hydrothermally prepared from the corresponding metal(ii) salts, H3dcna as a principal multifunctional ligand, and N-donor mediators of crystallization (1,10-phenanthroline, phen; 2,2'-bipyridine, bipy; 2,2'-biimidazole, H2biim; or 1,4-bis(pyrid-4-yl)benzene, bpb). The obtained products 1-9 were fully characterized by standard methods (elemental analysis, FTIR, TGA, PXRD) and the structures were established by single-crystal X-ray diffraction. These vary from the discrete monomers (1, 2) and dimers (5, 7) to the 1D (3, 4, 6) and 2D (8, 9) coordination polymers (CPs). Structural and topological characteristics of hydrogen-bonded or metal-organic architectures in 1-9 were highlighted, revealing that their structural multiplicity depends on the type of metal(ii) source and crystallization mediator. Thermal stability as well as luminescent, magnetic, or catalytic properties were explored for selected compounds. In particular, the zinc(ii) derivatives 3, 5, and 6 were applied as efficient heterogeneous catalysts for the cyanosilylation of aldehydes with trimethylsilyl cyanide at room temperature. The catalytic reactions were optimized by tuning the different reaction parameters (solvent composition, time, catalyst loading) and the substrate scope was also explored. Compound 5 revealed superior catalytic activity leading to up to 75% product yields, while maintaining its original performance upon recycling for at least four reaction cycles. Finally, the obtained herein products represent the unique examples of coordination compounds derived from H3dcna, thus opening up the use of this multifunctional tricarboxylic acid for generating complexes and coordination polymers with interesting structures and functional properties.