Study of Proton Conductivity of a 2D Flexible MOF and a 1D Coordination Polymer at Higher Temperature

We report the proton conduction properties of a 2D flexible MOF and a 1D coordination polymer having the molecular formulas {[Zn­(C₁₀H₂O₈)_0.5(C₁₀S₂N₂H₈)]·5H₂O]}_<i>n</i> (<b>1</b>) and {[Zn­(C₁₀H₂O₈)_0.5(C₁₀S₂N₂H₈)]·2H₂O]}_<i>n</i> (<b>2</b>), respectively. Compounds <b>1</b> and <b>2</b> show high conductivity values of 2.55 × 10^–7 and 4.39 × 10^–4 S cm^–1 at 80 °C and 95% RH. The conductivity value of compound <b>1</b> is in the range of those for previously reported flexible MOFs, and compound <b>2</b> shows the highest proton conductivity among the carboxylate-based 1D CPs. The dimensionality and the internal hydrogen bonding connectivity play a vital role in the resultant conductivity. Variable-temperature experiments of both compounds at high humidity reveal that the conductivity values increase with increasing temperature, whereas the variable humidity studies signify the influence of relative humidity on high-temperature proton conductivity. The time-dependent measurements for both compounds demonstrate their ability to retain conductivity up to 10 h

Third-Generation Breathing Metal–Organic Framework with Selective, Stepwise, Reversible, and Hysteretic Adsorption Properties

A new 2D interdigitated and highly flexible, breathing metal–organic framework has been synthesized through a diffusion technique by using the aldrithiol linker and pyromellitate ligand. The compound shows selective, stepwise, reversible, and hysteretic adsorption properties for CO₂ gas and H₂O, MeOH, and CH₃CN vapors

Study of Proton Conductivity of a 2D Flexible MOF and a 1D Coordination Polymer at Higher Temperature

We report the proton conduction properties of a 2D flexible MOF and a 1D coordination polymer having the molecular formulas {[Zn­(C₁₀H₂O₈)_0.5(C₁₀S₂N₂H₈)]·5H₂O]}_<i>n</i> (<b>1</b>) and {[Zn­(C₁₀H₂O₈)_0.5(C₁₀S₂N₂H₈)]·2H₂O]}_<i>n</i> (<b>2</b>), respectively. Compounds <b>1</b> and <b>2</b> show high conductivity values of 2.55 × 10^–7 and 4.39 × 10^–4 S cm^–1 at 80 °C and 95% RH. The conductivity value of compound <b>1</b> is in the range of those for previously reported flexible MOFs, and compound <b>2</b> shows the highest proton conductivity among the carboxylate-based 1D CPs. The dimensionality and the internal hydrogen bonding connectivity play a vital role in the resultant conductivity. Variable-temperature experiments of both compounds at high humidity reveal that the conductivity values increase with increasing temperature, whereas the variable humidity studies signify the influence of relative humidity on high-temperature proton conductivity. The time-dependent measurements for both compounds demonstrate their ability to retain conductivity up to 10 h

Single-Molecule Magnet Behavior of Confined Dy(III) in a Mixed Heteroatom-Substituted Polyoxotungstate

Two heteroatom-templated Dy(III)-confined polyoxotungstates [H2N(CH3)2]7Na7[Dy2(H2O)7(W4O9)(HPSeW15O54)(α-SeW9O33)2]·31H2O (1) and [H2N(CH3)2]14K2Na18{[Dy2(H2O)13W14O40]2[α-SeW9O33]4[HPSeW15O54]2}·44H2O (2) were synthesized by a one-pot aqueous reaction and structurally characterized. The most distinctive structural feature of complexes 1 & 2 is the simultaneous presence of both trivacant Keggin [α-SeW9O33]8– and Dawson [HPSeW15O54]10– building blocks containing P(III)–Se(IV) heteroatoms. The trimeric polyanion of 1 can be represented as a fusion of two trivacant Keggin [α-SeW9O33]8– and Dawson [HPSeW15O54]10– building units encapsulating the [Dy2(H2O)7(W4O9)]12+ cluster. On the other hand, hexameric polyoxoanions of 2 are described as four trivacant Keggin [α-SeW9O33]8– and two Dawson [HPSeW15O54]10–, building units anchoring a [Dy4(H2O)26W28O80]20+ cluster. The magnetic investigation revealed the presence of significant magnetic anisotropy and slow relaxation of magnetization behavior for complex 1 with a phenomenological energy barrier, Ueff = 13.58 K in the absence of an external magnetic field, and Ueff = 24.57 K in the presence of a 500 Oe external dc magnetic field. On the other hand, complex 2 favors the QTM relaxation process in the absence of an external magnetic field and shows field-induced slow relaxation of magnetization with Ueff = 11.11 K at 1500 Oe applied dc field. The in-depth analysis of magnetic relaxation dynamics shows that the relaxation process follows the Orbach as well as Raman relaxation pathways. Further, the ab initio calculation of the studied complexes confirms that the highly axial ground and first excited energy states (containing pure highest mJ states) are responsible for the observed single-molecule magnet (SMM) behavior. Remarkably, this is the first example of a mixed heteroatom-based Dy(III)-substituted polyoxotungstate with both trimeric Keggin [α-SeW9O33]8– and Dawson [HPSeW15O54]10– building units showing SMM behavior

Study of Heterogeneous Catalysis by Iron-Squarate based 3D Metal Organic Framework for the Transformation of Tetrazines to Oxadiazole derivatives

We present here a simple, milder, and environmentally benign heterogeneous catalytic method for the transformation of tetrazines to oxadiazole derivatives at room temperature (25 °C) using our earlier synthesized iron-squarate based 3D metal organic framework, [Fe₃(OH)₃(C₄O₄)­(C₄O₄)_0.5]_<i>n</i> (FeSq-MOF)

Densely Packed Lanthanide Cubane Based 3D Metal–Organic Frameworks for Efficient Magnetic Refrigeration and Slow Magnetic Relaxation

Two isostructural densely packed squarato-bridged lanthanide-based 3D metal–organic frameworks (MOFs) [Ln₅(μ₃-OH)₅(μ₃-O)­(CO₃)₂(HCO₂)₂(C₄O₄)­(H₂O)₂] [Ln = Gd (<b>1</b>) and Dy (<b>2</b>)] show giant cryogenic magnetic refrigeration (for <b>1</b>) and slow magnetic relaxation (for <b>2</b>). The structural analyses reveal the presence of a self-assembled crown-shaped building unit with a cubane-based rectangular moiety that leads to a special array of metal centers in 3D space in the complexes. Magnetic investigations confirm that complex <b>1</b> exhibits one of the largest cryogenic magnetocaloric effects among the molecular magnetic refrigerant materials reported so far (−Δ<i>S</i>_m = 64.0 J kg^–1 K^–1 for Δ<i>H</i> = 9 T at 3 K). The cryogenic cooling effect (of <b>1</b>) is also quite comparable with that of the commercially used magnetic refrigerant gadolinium–gallium garnet, whereas for complex <b>2</b>, slow relaxation of magnetization was observed below 10 K

Densely Packed Lanthanide Cubane Based 3D Metal–Organic Frameworks for Efficient Magnetic Refrigeration and Slow Magnetic Relaxation

Two isostructural densely packed squarato-bridged lanthanide-based 3D metal–organic frameworks (MOFs) [Ln₅(μ₃-OH)₅(μ₃-O)­(CO₃)₂(HCO₂)₂(C₄O₄)­(H₂O)₂] [Ln = Gd (<b>1</b>) and Dy (<b>2</b>)] show giant cryogenic magnetic refrigeration (for <b>1</b>) and slow magnetic relaxation (for <b>2</b>). The structural analyses reveal the presence of a self-assembled crown-shaped building unit with a cubane-based rectangular moiety that leads to a special array of metal centers in 3D space in the complexes. Magnetic investigations confirm that complex <b>1</b> exhibits one of the largest cryogenic magnetocaloric effects among the molecular magnetic refrigerant materials reported so far (−Δ<i>S</i>_m = 64.0 J kg^–1 K^–1 for Δ<i>H</i> = 9 T at 3 K). The cryogenic cooling effect (of <b>1</b>) is also quite comparable with that of the commercially used magnetic refrigerant gadolinium–gallium garnet, whereas for complex <b>2</b>, slow relaxation of magnetization was observed below 10 K

Densely Packed Lanthanide Cubane Based 3D Metal–Organic Frameworks for Efficient Magnetic Refrigeration and Slow Magnetic Relaxation

Two isostructural densely packed squarato-bridged lanthanide-based 3D metal–organic frameworks (MOFs) [Ln₅(μ₃-OH)₅(μ₃-O)­(CO₃)₂(HCO₂)₂(C₄O₄)­(H₂O)₂] [Ln = Gd (<b>1</b>) and Dy (<b>2</b>)] show giant cryogenic magnetic refrigeration (for <b>1</b>) and slow magnetic relaxation (for <b>2</b>). The structural analyses reveal the presence of a self-assembled crown-shaped building unit with a cubane-based rectangular moiety that leads to a special array of metal centers in 3D space in the complexes. Magnetic investigations confirm that complex <b>1</b> exhibits one of the largest cryogenic magnetocaloric effects among the molecular magnetic refrigerant materials reported so far (−Δ<i>S</i>_m = 64.0 J kg^–1 K^–1 for Δ<i>H</i> = 9 T at 3 K). The cryogenic cooling effect (of <b>1</b>) is also quite comparable with that of the commercially used magnetic refrigerant gadolinium–gallium garnet, whereas for complex <b>2</b>, slow relaxation of magnetization was observed below 10 K

Synthesis and Characterization of Polyhedral-Based Metal–Organic Frameworks Using a Flexible Bipyrazole Ligand: Topological Analysis and Sorption Property Studies

Six porous metal–organic frameworks (MOFs), {[Ni­(BTC)_0.66­(BPz)₂]­·2MeOH­·4H₂O}_<i>n</i> (<b>1</b>), {[Co­(BTC)_0.66­(BPz)₂]­·2MeOH­·4H₂O}<i>_n</i> (<b>2</b>), {[Mn­(BTC)_0.66­(BPz)₂]­·2MeOH­·4H₂O}_<i>n</i> (<b>3</b>), {[Cd­(BDC)­(BPz)­(H₂O)]­·2MeOH­·DMF}<i>_n</i> (<b>4</b>), {[Cd₂(NH₂-BDC)₂­(BPz)­(H₂O)]­·MeOH­·H₂O­·DMF}<i>_n</i> (<b>5</b>), and {[Co­(BDC)­(BPz)­(H₂O)]}<i>_n</i> (<b>6</b>) (where H₃BTC = 1,3,5-benzenetricarboxylic acid, H₂BDC = 1,4-benzenedicarboxylic acid, NH₂-H₂BDC = 2-amino-1,4-benzenedicarboxylic acid, and BPz = 3,3′,5,5′-tetramethyl-4,4′-bipyrazole), were obtained through a solvent diffusion technique and characterized. The networks exhibit a variety of topologies: <b>1</b>, <b>2</b>, and <b>3</b> are isostructural and possess octahedral and cuboctahedra type cages and exhibit 3,6-c binodal net having <i><b>loh</b></i><b>1</b> topology, <b>4</b> is a two-dimensional MOF having one-dimensional open channels with a 4-c uninodal net having <i><b>sql</b></i> topology, <b>5</b> exhibits a three-dimensional (3D) porous MOF having a 3,3,4,8-c net with a new topology having the name, <i><b>skr</b></i><b>1</b>, whereas <b>6</b> discloses a 3D nonporous network which exhibits a 4-c uninodal net having CdSO₄ topology. Being isostructural, gas sorption studies of <b>1</b>–<b>3</b> show nearly the same CO₂ sorption at 195 K of ∼90 mL g^–1, whereas <b>4</b> and <b>5</b> show a maximum uptake of 42 and 37 mL g^–1 at 195 K. Vapor sorption studies of <b>1</b>–<b>3</b> reveal stepwise uptake of water with a final amount reached to nearly 350 mL g^–1, whereas <b>4</b> and <b>5</b> show maximum uptake of 110 and 90 mL g^–1, respectively. Compared to the free ligand BPz, photoluminescence studies of <b>4</b> and <b>5</b> show red shifts and emit in the blue-green region with λ_max at 430 and 472 nm for <b>4</b> and <b>5</b>, respectively

A Family of Metal–Organic Frameworks Based on Carboxylates and a Neutral, Long, and Rigid Ligand: Their Structural Revelation, Magnetic, and Luminescent Property Study

Four new two-dimensional/three-dimensional (2D/3D) bpmh-based metal organic frameworks, namely, {[Zn­(1,3-adaa)­(bpmh)]}_<i>n</i> (<b>1</b>), {[Cd­(1,3-adaa)­(bpmh)]}<i>_n</i> (<b>2</b>), {[Zn­(1,4-pdaa)­(bpmh)]}_<i>n</i> (<b>3</b>), and {[Co­(1,4-pdaa)­(bpmh)]}_<i>n</i> (<b>4</b>) (bpmh = <i>N</i>,<i>N</i>-bis-pyridin-4-ylmethylene-hydrazine, 1,3-adaa = 1,3-adamantane diacetic acid, 1,4-pdaa = 1,4-phenylene diacetic acid) have been synthesized through the slow diffusion technique. Structural determination reveals that compounds <b>1</b> and <b>2</b> have 2D layered architectures with similar framework topology, whereas <b>3</b> and <b>4</b> are isostuctural 3D frameworks. Both <b>1</b> and <b>2</b> perceives a common secondary building unit (SBU) [M₂(adaa)₄(bpmh)₄] [M = Zn­(<b>1</b>) and Cd­(<b>2</b>)]. In compound <b>1</b>, 1,3-adaa exhibits both μ- 1,1 and μ- 1,2 bridging modes, whereas in <b>2</b> it shows both μ-1,1 and μ-1,1,2 bridging modes. The difference in the bridging mode of 1,3-adaa in <b>1 </b>(Zn) and <b>2 </b>(Cd) is responsible for the shorter M···M contacts in <b>2</b> (3.872 Å) than in <b>1</b> (4.13 Å) in the SBU. The 1,3-adaa ligands are sandwiched between the bpmh linkers in compounds <b>1</b> and <b>2.</b> In compounds <b>3</b> and <b>4</b>, 1,4-pdaa exhibits both μ-1 and μ-1,1 bridging modes and are isostructural in nature. The metal centers are arranged in a helical fashion around 2₁ screw axis in <b>3</b> and <b>4</b>. In compounds <b>1</b>–<b>4</b>, the used dicarboxylic acids act as pillars between the metal-bpmh layers. Solid-state photoluminescent properties of compounds <b>1</b>–<b>3</b> show ligand (n → π* and π → π*)-based florescence. The magnetic studies of compound <b>4</b> show presence of the antiferromagnetic exchange between the metal centers