Efficient and Selective Removal of Copper(II) from Aqueous Solution by a Highly Stable Hydrogen-Bonded Metal–Organic Framework

Copper­(II) is an indispensable element in nature, while exposure to excessive Cu²⁺ will potentially cause health issues. It is imperative to develop new strategies for efficient Cu²⁺ uptake from aqueous solution. Herein, a hydrogen-bonded metal–organic framework (MOF) [(Zn₃L₃(H₂O)₆]­[(Na)­(NO₃)] (<b>1</b>) with high stability was elaborately constructed. The uncoordinated carboxylate oxygen atoms in the channels of MOF were designed as active sites to recognize Cu²⁺ and further coordinate with it. Without pretreatment, MOF <b>1</b> demonstrated a relatively high adsorption capacity (379.13 mg g^–1), exceeding most Cu²⁺ adsorbents. Even with the existence of different metal ions and a high concentration of interfering ions, highly selective adsorption of Cu²⁺ can be achieved. Moreover, the excellent water stability together with the high removal efficiency in the presence of coexisting ions offers MOF <b>1</b> the possibility in practical application. The mechanism for Cu²⁺ selective adsorption was systematically investigated by UV–vis, Fourier transform infrared, and fluorescence lifetime techniques, which may originate from the strong interaction between Cu²⁺ and the carboxylate oxygen atoms. Our work may open an avenue to develop MOFs into adsorbent materials for water pollutants

High Efficiency and Fast Removal of Trace Pb(II) from Aqueous Solution by Carbomethoxy-Functionalized Metal–Organic Framework

Lead (Pb) is one of the most widespread toxic heavy metals, and how to quickly and completely remove trace Pb­(II) is a global concern. Herein, we prepared a novel metal–organic framework (MOF) {[Cd­(ADB)­L₂]·1.5DMF·2H₂O}_<i>n</i> (<b>1</b>) decorated with carbomethoxy groups and investigated the Pb­(II) removal performance as well as the underlying mechanism. The MOF exhibits a fast kinetics with the kinetic rate constant <i>k</i>₂ of 0.162 g mg^–1 min^–1, which is 1–3 orders of magnitude higher than the reported Pb­(II) adsorbent materials. In addition, even in a concentration of 0.1 ppm, a high removal efficiency (96%) was still obtained after the treatment with the metal–organic framework, and the concentration was reduced to 0.004 ppm, which is well below the drinking water standard of the World Health Organization (0.01 ppm). The possible adsorption mechanism was systematically verified by Fourier-transform infrared and X-ray photoelectron spectroscopy investigations. The significant affinity between carbomethoxy groups and Pb­(II) is responsible for the good removal performance

Guest Molecule Release Triggers Changes in the Catalytic and Magnetic Properties of a Fe^II-Based 3D Metal–Organic Framework

A Fe^II-based metal–organic framework (MOF), {[Fe₂(pbt)₂(H₂O)₂]·2H₂O}_<i>n</i>, undergoes an irreversible dehydration, which triggers changes in the catalytic and magnetic properties of the MOF. These property changes are attributed to the high-spin to low-spin transition of 7.1% center Fe^II, which is demonstrated by ⁵⁷Fe Mössbauer, X-ray photoelectron spectroscopy, and UV/vis absorption spectra

Three New Hg(II) Complexes Constructed From Mercapto- and Amino-Containing Triazole Ligands: Syntheses, Crystal Structures, and Luminescent Properties

<div><p>Three new mercury(II) complexes [HgI₂(3-aptt)₂] (1), [Hg(4-aptt)₂] (2), and [Hg(a-mtt)₂]·H₂O (3) were synthesized based on three structurally related ligands: 4-amino-3-(3-pyridyl)-1H-1,2,4-triazole-5-thione (3-Haptt), 4-amino-3-(4-pyridyl)-5-mercapto-1,2,4-triazole (4-Haptt), and 4-amino-3-methyl-1,2,4-triazoline-5-thiadone (a-Hmtt). The structures of complexes 1–3 were determined by single-crystal X-ray diffraction techniques and further characterized by elemental analyses and IR spectra. The results reveal that these three complexes take mononuclear structures. And although various weak interactions, including N‒H···I and N···H‒O H-bondings as well as N_trz···N_py and π···π stacking, play significant roles in crystal structures, just these weak interactions link the mononuclear units into higher dimensional supramolecular networks. Their thermal stabilities and the solid state luminescent properties have also been discussed.</p></div

Effect of Organic Polycarboxylate Ligands on the Structures of a Series of Zinc(II) Coordination Polymers Based on a Conformational Bis-triazole Ligand

To explore the influence of six structurally different polycarboxylate ligands H₂L¹ to H₄L⁶ in the system Zn­(II)/btmx, six coordination polymers, formulated as [Zn­(btmx)­(L¹)]_<i>n</i> (<b>1</b>), {[Zn­(btmx)­(L²)]·2H₂O}_<i>n</i> (<b>2</b>), {[Zn­(btmx)­(L³)]·1.5H₂O}_<i>n</i> (<b>3</b>), [Zn­(btmx)­(L⁴)]_<i>n</i> (<b>4</b>), {[Zn₄(btmx)₃(L⁵)₄(H₂O)₂]·4H₂O}_<i>n</i> (<b>5</b>), and [Zn­(btmx)­(H₂L⁶)]_<i>n</i> (<b>6</b>), have been obtained under similar conditions (btmx = 1,4-bis­(1,2,4-triazol-1-ylmethyl)-2,3,5,6-tetramethylbenzene, H₂L¹ = 1,3-benzenedicarboxylic acid, H₂L² = 1,4-benzenedicarboxylic acid, H₂L³ = 1,3-adamantanedicarboxylic acid, H₂L⁴ <b>=</b> 1,3-adamantanediacetic acid, H₂L⁵ = 4,4′-oxidibenzoic acid, and H₄L⁶ = 3,3′,4,4′-benzophenone tetracarboxylic acid). The structure determination reveals that complexes <b>1</b> and <b>4</b> are two-dimensional (2D) layered networks and exhibit typical (4,4) topological nets. Complex <b>2</b> shows an undulating 2D (4,4)-network with 2-fold interpenetration. Complex <b>3</b> possesses a three-dimensional (3D) 3-fold interpenetrating 4-connected framework of 6⁶-<b>dia</b> topology. Both <b>5</b> and <b>6</b> have different 3D interpenetrated motifs generated by 2D → 3D interpenetration. Complex <b>5</b> belongs to a 3D framework built from the interpenetration of 2D bilayers in an inclined mode, while <b>6</b> involves a parallel interpenetration between the adjacent 2D (4,4) layers. This work markedly indicates that the effect of polycarboxylate ligands is significant in the construction of these networks

Polynuclear Cd^II Polymers: Crystal Structures, Topologies, and the Photodegradation for Organic Dye Contaminants

To systematically explore the effect of polynuclear complexes on photocatalytic degradation of the organic dyes, a series of coordination complexes containing Cd^II clusters, formulated as {[Cd₃L₂(H₂O)₅]·H₂O}_<i>n</i> (<b>1</b>), {[Cd₃L₂(hbmb)­(H₂O)₂]·2.5H₂O}_<i>n</i> (<b>2</b>), {[Cd₃L₂(btbb)­(H₂O)₂]·2EtOH·1.5H₂O}_<i>n</i> (<b>3</b>), and {[Cd₆L₄(bipy)₂(H₂O)₆]·3H₂O}_<i>n</i> (<b>4</b>) (H₃L = 3,4-bi­(4-carboxyphenyl)-benzoic acid, hbmb = 1,1′-(1,6-hexane)­bis­(2-methylbenzimidazole), btbb = 1,4-bis­(2-(4-thiazolyl)­benzimidazole-1-ylmethyl)­benzene, 4,4′-bipy = 4,4′-bipyridine), have been designed and synthesized. Complex <b>1</b> based on trinuclear Cd^II clusters exhibits a new (3,3,6)-connected 3D framework. <b>2</b> belongs to a (3,3,8,8)-connected tfz-d topology net with pillar-layered frameworks assembled by two kinds of trinuclear Cd^II clusters. <b>3</b> is a 3D pillar-layered framework, which features a (3,8)-connected tfz-d net based upon one kind of trinuclear Cd^II cluster. <b>4</b> presents a new 3D (3,6,10)-connected framework with dinuclear and tetranuclear clusters. The photocatalytic properties of complexes <b>1</b>–<b>4</b> have been studied in detail. Remarkably, <b>1</b>–<b>4</b> all reveal good photocatalytic activity in MB/MO degradation. The optical energy gap calculated by the diffuse reflectivity spectra of <b>1</b>–<b>4</b> are consistent with their degradation rates. Moreover, the experimental results further demonstrate that the cluster complexes containing different kinds of nuclei may exert different impact on the decomposition of disparate organic dyes

Chiral Metallocycles Templated Novel Chiral Water Frameworks

An intentionally synthesized chiral terpyridyl ligand <i>S</i>-2­(4-(2,6-di­(pyridin-2-yl)­pyridin-4-yl)-benzylamino)­propanoic acid (H₂L) was used to construct two chiral Ni^II complexes, [Ni₂­(HL)₂­(N₃)­(H₂O)]­(N₃)·19H₂O (<b>1</b>) and [Ni₂­(HL)₂­(N₃)₂]·7H₂O (<b>2</b>). Both complexes are dinuclear metallocyclic complexes. The monoanionic form (HL)⁻ of the chiral ligand coordinates to the metal centers in a bichelating antiparallel fashion to form the metallomacrocycles where the chiral metallocycles Ni₂(HL)₂ template the formation of a novel chiral 3D zeolite-like water framework with nanometer cages trapping the metallocycles or anchor chiral water chains in the 1D channels of a resulting chiral 3D supermolecule, respectively

Ni(II) Coordination Polymers Constructed from the Flexible Tetracarboxylic Acid and Different N‑Donor Ligands: Structural Diversity and Catalytic Activity

To seek the effect that condition of the complexes has on the manufacture of the biaryl compounds, seven Ni­(II) complexes, namely, {[Ni­(L)_0.5(bpa)­(H₂O)]·2H₂O}_<i>n</i> (<b>1</b>), {[Ni₂(L)­(dpp)₂­(H₂O)]·4H₂O}_<i>n</i> (<b>2</b>), {[Ni­(L)_0.5(pbmb)­(H₂O)]·H₂O}_<i>n</i> (<b>3</b>), {[Ni₂(L)­(bmp)₂­(H₂O)]·7H₂O}_<i>n</i> (<b>4</b>), {[Ni­(L)_0.5­(pbib)_1.5]·2H₂O}_<i>n</i> (<b>5</b>), {[Ni₂(L)­(pbib)_1.5]·3H₂O}_<i>n</i> (<b>6</b>), and [Ni­(L)_0.5­(beb)₂­(H₂O)]_<i>n</i> (<b>7</b>) (bpa = 1,2-bis­(4-pyridyl)­ethane, dpp = 1,3-di­(4-pyridyl)­propane, pbmb = 1,1′-(1,3-propane)­bis­(2-methylbenzimidazole), bmp = 1,5-bis­(2-methylbenzimidazol) pentane, pbib = 1,4-bis­(imidazol-1-ylmethyl)­benzene, beb = 1,4-bis­(2-ethylbenzimidazol-1-ylmethyl)­benzene), have been gained through hydro­(solvo)­thermal reactions of 5,5′-(hexane-1,6-diyl)-bis­(oxy)­diisophthalic acid ligand (H₄L) with Ni­(II) metal ions under the regulation and control of six N-donor ligands. 3-fold interpenetrating complex <b>1</b> belongs to a (4,4)-connected 3D <i>bbf</i> net with a vertex symbol of (6⁴·8²)­(6⁶) topology. 3-fold interpenetrating complex <b>2</b> presents a (4,4,4)-connected 3D <i>bbf</i> net with a Schläfli symbol of (6⁶)₂(6⁴·8²) topology. <b>3</b> features a (3,4)-connected <i>3,4L13</i> topology with a Schläfli symbol of (4·6²)­(4²·6²·8²) topology. <b>4</b> possesses a (4,4,4)-connected <i>mog Moganite</i> 3D network fabric, and the vertex symbol is (4·6⁴·8)₂­(4²·6²·8²). <b>5</b> takes on a (4,5)-connected architecture, and the point symbol is (4·6⁹)­(4²·6⁶·8²). <b>6</b> is a (4,7)-connected framework, and the Schläfli symbol is (4⁵·5)­(4⁷·5³·6¹¹). <b>7</b> has a (4,4)-connected <i>4,4L28</i> topology, and the point (Schläfli) symbol is (4²·6⁴)­(4·6⁴·8). A systematic structural comparison of <b>1</b>–<b>7</b> signifies that their frameworks can be regulated through varied conformations of the flexible H₄L ligand and diverse N-donor ligands. Between the proximal Ni­(II) ions, the variable-temperature (2–300 K) magnetic susceptibilities of <b>6</b> display overall weak antiferromagnetic coupling. In the complexes-catalyzed homocoupling reaction of iodobenzene, <b>3</b>, <b>5</b>, <b>6</b>, and <b>7</b> have been verified to be effectual catalysts for the synthesis of the biaryl compounds

Effect of Organic Polycarboxylate Ligands on the Structures of a Series of Zinc(II) Coordination Polymers Based on a Conformational Bis-triazole Ligand

To explore the influence of six structurally different polycarboxylate ligands H₂L¹ to H₄L⁶ in the system Zn­(II)/btmx, six coordination polymers, formulated as [Zn­(btmx)­(L¹)]_<i>n</i> (<b>1</b>), {[Zn­(btmx)­(L²)]·2H₂O}_<i>n</i> (<b>2</b>), {[Zn­(btmx)­(L³)]·1.5H₂O}_<i>n</i> (<b>3</b>), [Zn­(btmx)­(L⁴)]_<i>n</i> (<b>4</b>), {[Zn₄(btmx)₃(L⁵)₄(H₂O)₂]·4H₂O}_<i>n</i> (<b>5</b>), and [Zn­(btmx)­(H₂L⁶)]_<i>n</i> (<b>6</b>), have been obtained under similar conditions (btmx = 1,4-bis­(1,2,4-triazol-1-ylmethyl)-2,3,5,6-tetramethylbenzene, H₂L¹ = 1,3-benzenedicarboxylic acid, H₂L² = 1,4-benzenedicarboxylic acid, H₂L³ = 1,3-adamantanedicarboxylic acid, H₂L⁴ <b>=</b> 1,3-adamantanediacetic acid, H₂L⁵ = 4,4′-oxidibenzoic acid, and H₄L⁶ = 3,3′,4,4′-benzophenone tetracarboxylic acid). The structure determination reveals that complexes <b>1</b> and <b>4</b> are two-dimensional (2D) layered networks and exhibit typical (4,4) topological nets. Complex <b>2</b> shows an undulating 2D (4,4)-network with 2-fold interpenetration. Complex <b>3</b> possesses a three-dimensional (3D) 3-fold interpenetrating 4-connected framework of 6⁶-<b>dia</b> topology. Both <b>5</b> and <b>6</b> have different 3D interpenetrated motifs generated by 2D → 3D interpenetration. Complex <b>5</b> belongs to a 3D framework built from the interpenetration of 2D bilayers in an inclined mode, while <b>6</b> involves a parallel interpenetration between the adjacent 2D (4,4) layers. This work markedly indicates that the effect of polycarboxylate ligands is significant in the construction of these networks

Template-Assisted Synthesis of Co,Mn-MOFs with Magnetic Properties Based on Pyridinedicarboxylic Acid

To investigate the influence of organic molecules with reactive functional groups as templates on the structures of the resulting MOFs, four novel complexes based on the pyridyl carboxylic acid ligand 5-(pyridin-4-yl)­isophthalic acid (H₂pyip), namely, [Mn₃(pyip)₂(HCOO)₂(H₂O)₂]_<i>n</i> (<b>1</b>), {[Co­(pyip)­(H₂O)]·H₂O}_<i>n</i> (<b>2</b>), {[Mn₂(pyip)₂(H₂O)₄]·5H₂O}_<i>n</i> (<b>3</b>), and [Co­(pyip)­(EtOH)­(H₂O)]_<i>n</i> (<b>4</b>), have been synthesized under solvothermal conditions. In the presence of 4,4′-bipyridyl as the template, 3D coordination framework <b>1</b> with the Schläfli symbol of (4·6·7) (4²·5·6⁵·7³·8²·9·11) was obtained. Using cyanoacetic acid as the template, we obtained 2D double-layered structure <b>2</b> with the Schläfli symbol of (4³) (4⁶·6⁶·8³). <b>3</b> and <b>4</b> are prepared in the absence of a templating agent. <b>3</b> features an infinite 2D network with a 1D water chain penetrating the 1D channel and further results in a 3D supramolecule through hydrogen-bond interactions. <b>4</b> contains two independent 2D networks that are further connected to a 2D double-layered supramolecular framework by hydrogen bonds. The template-assisted method is a potential approach for obtaining specific intriguing complexes that might be difficult to access by routine synthetic methods. Magnetic investigations revealed that both <b>1</b> and <b>2</b> exhibit weak antiferromagnetic interactions mediated by pyip^2–