Guest-Induced Irreversible Sliding in a Flexible 2D Rectangular Grid with Selective Sorption Characteristics

A 2D noninterpenetrated flexible metal-organic porous solid, {[Cu2(cis-chdc)2(bpee)]·H2O}n (1) based on a paddle-wheel building unit has been constructed using a mixed-ligand system. Guest-induced irreversible internetwork displacements of the 2D grids result in permanent porosity in the framework, as realized by the selective CO2 sorption over N2. The different affinity and selectivity of the solvent molecules was correlated with the internal polarity of the pore surfaces

Guest-Induced Irreversible Sliding in a Flexible 2D Rectangular Grid with Selective Sorption Characteristics

A 2D noninterpenetrated flexible metal-organic porous solid, {[Cu2(cis-chdc)2(bpee)]·H2O}n (1) based on a paddle-wheel building unit has been constructed using a mixed-ligand system. Guest-induced irreversible internetwork displacements of the 2D grids result in permanent porosity in the framework, as realized by the selective CO2 sorption over N2. The different affinity and selectivity of the solvent molecules was correlated with the internal polarity of the pore surfaces

Guest-Specific Double- or Single-Step Adsorption in a Flexible Porous Framework Based on a Mixed-Ligand System

A 2D flexible metal−organic porous solid, {[Ni(1,3-adc)(bpp)(H2O)2](H2O)(EtOH)}n (1), has been synthesized using flexible organic linkers. The desolvated framework, {[Ni(1,3-adc)(bpp)]}n (1′), undergoes structural contraction and exhibits double-step hysteretic adsorption for CO2, H2O, and MeOH and single-step gate-opening behavior with EtOH. These observations are correlated with the effect of the polarity and window dimension of the pore to the corresponding adsorbate molecules

Temperature- and Stoichiometry-Controlled Dimensionality in a Magnesium 4,5-Imidazoledicarboxylate System with Strong Hydrophilic Pore Surfaces

1D, 2D, and 3D three metal−organic hybrid frameworks of MgII have been synthesized using 4,5-imidazoledicarboxylic acid (H3idc) with control of the temperature and stoichiometry in a hydrothermal technique. All of the frameworks show high thermal stability, and frameworks 1D and 3D provide highly hydrophilic pore surfaces, correlated by the selective sorption of water molecules over the organic vapor and other gases like N2 and CO2

Stoichiometry-Controlled Two Flexible Interpenetrated Frameworks: Higher CO₂ Uptake in a Nanoscale Counterpart Supported by Accelerated Adsorption Kinetics

Here, we report the synthesis, structural characterizations, and gas storage properties of two new 2-fold interpenetrated 3D frameworks, {[Zn2(bpdc)2(azpy)]·2H2O·2DMF}n (1) and {[Zn3(bpdc)3(azpy)]·4H2O·2DEF}n (2) [bpdc = 4,4′-biphenyldicarboxylate; azpy = 4,4′-azobipyridine], obtained from the same set of organic linkers. Furthermore, 1 has been successfully miniaturized to nanoscale (MOF1N) of spherical morphology to study size dependent adsorption properties through a coordination modulation method. The two different SBUs, dinuclear paddle-wheel {Zn2(COO)4} for 1 and trinuclear {Zn3(μ2-OCO)2(COO)4 }­for 2, direct the different network topologies of the frameworks that render different adsorption characteristics into the systems. Both of the frameworks show guest induced structural transformations as supported by PXRD studies. Adsorption studies of 1 and 2 show CO2 selectivity over several other gases (such as N2, H2, O2, and Ar) under identical experimental conditions. Interestingly, MOF1N exhibits significantly higher CO2 storage capacity compared to bulk crystals of 1 and that can be attributed to the smaller diffusion barrier at the nanoscale that is supported by studies of adsorption kinetics in both states. Kinetic measurement based on water vapor adsorption clearly distinguishes between the rate of diffusion of bulk (1) and nanospheres (MOF1N). The respective kinetic rate constant (k, s–1) for MOF1N (k = 1.29 × 10–2 s–1) is found to be considerably higher than 1 (k = 7.1 × 10–3 s–1) as obtained from the linear driving force (LDF) model. This is the first account where a new interpenetrated MOF has been scaled down to nanoscale through a coordination modulation method, and their difference in gas uptake properties has been correlated through a higher rate of mass diffusion as obtained from kinetics of adsorption

Temperature-Controlled Synthesis of Metal-Organic Coordination Polymers: Crystal Structure, Supramolecular Isomerism, and Porous Property

Five new supramolecular metal-organic coordination polymers (MOCPs), {[Ni(bipy) (H2O)4](2,6-nds)·4H2O} (1), {[Ni(bipy)(H2O)4](2,6-nds)·2H2O} (2), {[Ni (bipy)(H2O)4](2,6-nds)} (3), {[Ni (bipy)(H2O)4](2,6-nds)} (4), {[Cu (bipy)(H2O)4](2,6-nds)} (5) (bipy = 4,4′-bipyridyl; 2,6-nds = 2,6-naphthalenedisulphonate) have been synthesized and structurally characterized. Compounds 1 and 5 were synthesized at room temperature in H2O/EtOH medium, whereas 2−4 were isolated under hydrothermal conditions. Compounds 1−4 were synthesized maintaining the same stoichiometric ratio of metal and ligand under different reaction temperatures, and the different structures of the compounds indicate that the temperature plays a significant role in the construction of the coordination polymers. Structural characterization reveals that the one-dimensional [M(bipy)(H2O)4]2+ cationic chain is a basic building unit for all of the MOCPs, while 2,6-nds remains as a counteranion. In all cases, 2,6-nds counteranions interact with water and bipy molecules through strong hydrogen-bonding and π−π interactions to afford three-dimensional supramolecular structures. Compounds 1−4 have the same building unit with different network superstructures and are related as supramolecular isomers. Supramolecular isomerism in 3 and 4 is very interesting since they have the same molecular formula, {[Ni(bipy)(H2O)4](2,6-nds)}, and are polymorphs. Compounds 4 and 5 are isomorphous. The thermogravimetric study suggests that the dehydrated compounds are stable up to 300 °C. Furthermore, sorption studies suggest that dehydrated compounds of 1 and 2 are permanently porous

Bifunctional Co(II)–Ag(I) and Ni(II)–Ag(I) Frameworks: Modulation of Magnetic Property and CO₂ Uptake Based on Organic Pillars

This report articulates synthesis, characterization, adsorption, and magnetic properties of four bimetallic Co­(II)– or Ni­(II)–Ag­(I) 3D porous frameworks based on mixed-ligand systems. The cyanide-bridged M­(II)–Ag­(I) bimetallic compounds with the general formula [M^II(L)­{Ag­(CN)₂}₂·<i>x</i>H₂O]_<i>n</i> [<b>1</b>, L = piperazine, M = Co; <b>2</b>, L = piperazine, M = Ni; <b>3</b>, L = 1,4-diazabicyclo[2.2.2]­octane (dabco), M = Co; <b>4</b>, L = pyrazine, M = Co] have been synthesized by liquid phase diffusion method at room temperature. Structure determination revealed that all these compounds have α-polonium type structural topology. The Ag­(CN)₂^– metallo-ligand has been used to generate 2D −M­(II)–CN–Ag­(I)–CN–M­(II)– layers, which are further linked by different organic pillars to construct a 3D bimetallic Co­(II)– or Ni­(II)–Ag­(I) porous pillared-layered structure. The magnetic and adsorption properties of these systems have been tuned by systematic variation of the pillars such as piperazine, pyrazine, and dabco. Temperature dependent magnetic study reveals that at low temperature, magnetized states exist for <b>1</b>, <b>2</b>, and <b>3</b> and spin canting behavior is evident; while <b>4</b> exhibits dominant antiferromagnetism. The degree of spin canting/antiferromagnetism depends on the organic spacers. These compounds contain water filled channels, and desolvated frameworks show high thermal stability and structural rigidity. Compounds <b>1</b>, <b>2</b>, and <b>4</b> exhibit permanent porosity as established by gas adsorption studies whereas <b>3</b> does not adsorb any gas unveiling that pore size could be modulated by changing the organic pillars. In the case of <b>3</b>, the larger pillar dabco reduces pore size significantly resulting in a nonporous structure. Furthermore, compound <b>1</b> reveals selective CO₂ uptake properties at 195 K as other gases (N₂, H₂, O₂, and Ar) show only surface adsorption, suggesting that quadrupolar CO₂ molecules interact effectively with the pore surfaces decorated with polar −CN groups

Transformation from a 2D Stacked Layer to 3D Interpenetrated Framework by Changing the Spacer Functionality: Synthesis, Structure, Adsorption, and Magnetic Properties

Two novel coordination polymers of Cu(II), viz. [Cu(bipy)(1,4-napdc)(H2O)2]n (1) and {[Cu(bpe)1.5(1,4-napdc)](H2O)}n (2) (bipy = 4,4‘-bipyridine; bpe = 1,2-bis(4-pyridyl)ethane; 1,4-napdc2- = 1,4-naphthalenedicarboxylate), have been synthesized and structurally characterized by changing only the pillar motifs. Both the compounds crystallize by slow evaporation from the ammoniacal solution of the as-synthesized solid. Framework 1 crystallizes in monoclinic crystal system, space group P2/n (No. 13), with a = 11.028(19) Å, b = 11.16(3) Å, c = 7.678(13) Å, β = 103.30(5)°, and Z = 2. Framework 2 crystallizes in triclinic system, space group, P1̄ (No. 2), a = 10.613(4) Å, b = 10.828(10) Å, c = 13.333(9) Å, α = 85.25(9)°, β = 82.59(6)°, γ = 60.37(5)°, and Z = 2. The structure determination reveals that 1 has a 2D network based on rectangular grids, where each Cu(II) is in 4 + 2 coordination mode. The 2D networks stacked in a staggered manner through the π−π interaction to form a 3D supramolecular network. In the case of 2, a {Cu(bpe)1.5}n ladder connected by 1,4-napdc2- results a 2D cuboidal bilayer network and each bilayer network is interlocked by two adjacent identical network (upper and lower) forming 3-fold interpenetrated 3D framework with small channel along the c-axis, which accommodates two water molecules. The TGA and XRPD measurements reveal that both the frameworks are stable after dehydration. Adsorption measurements (N2, CO2, and different solvents, like H2O, MeOH, etc.) were carried out for both frameworks. Framework 1 shows type-II sorption profile with N2 in contrast to H2O and MeOH, which are chemisorbed in the framework. In case of 2, only H2O molecules can diffuse into the micropore, whereas N2, CO2, and MeOH cannot be adsorbed, as corroborated by the smaller channel aperture. The low-temperature (300−2 K) magnetic measurement of 1 and 2 reveals that both are weakly antiferromagnetically coupled (J = −1.85 cm-1, g = 2.02; J = −0.153 cm-1, g = 2.07), which is correlated by the magnetic pathway to the corresponding structure

Transformation from a 2D Stacked Layer to 3D Interpenetrated Framework by Changing the Spacer Functionality: Synthesis, Structure, Adsorption, and Magnetic Properties

Two novel coordination polymers of Cu(II), viz. [Cu(bipy)(1,4-napdc)(H2O)2]n (1) and {[Cu(bpe)1.5(1,4-napdc)](H2O)}n (2) (bipy = 4,4‘-bipyridine; bpe = 1,2-bis(4-pyridyl)ethane; 1,4-napdc2- = 1,4-naphthalenedicarboxylate), have been synthesized and structurally characterized by changing only the pillar motifs. Both the compounds crystallize by slow evaporation from the ammoniacal solution of the as-synthesized solid. Framework 1 crystallizes in monoclinic crystal system, space group P2/n (No. 13), with a = 11.028(19) Å, b = 11.16(3) Å, c = 7.678(13) Å, β = 103.30(5)°, and Z = 2. Framework 2 crystallizes in triclinic system, space group, P1̄ (No. 2), a = 10.613(4) Å, b = 10.828(10) Å, c = 13.333(9) Å, α = 85.25(9)°, β = 82.59(6)°, γ = 60.37(5)°, and Z = 2. The structure determination reveals that 1 has a 2D network based on rectangular grids, where each Cu(II) is in 4 + 2 coordination mode. The 2D networks stacked in a staggered manner through the π−π interaction to form a 3D supramolecular network. In the case of 2, a {Cu(bpe)1.5}n ladder connected by 1,4-napdc2- results a 2D cuboidal bilayer network and each bilayer network is interlocked by two adjacent identical network (upper and lower) forming 3-fold interpenetrated 3D framework with small channel along the c-axis, which accommodates two water molecules. The TGA and XRPD measurements reveal that both the frameworks are stable after dehydration. Adsorption measurements (N2, CO2, and different solvents, like H2O, MeOH, etc.) were carried out for both frameworks. Framework 1 shows type-II sorption profile with N2 in contrast to H2O and MeOH, which are chemisorbed in the framework. In case of 2, only H2O molecules can diffuse into the micropore, whereas N2, CO2, and MeOH cannot be adsorbed, as corroborated by the smaller channel aperture. The low-temperature (300−2 K) magnetic measurement of 1 and 2 reveals that both are weakly antiferromagnetically coupled (J = −1.85 cm-1, g = 2.02; J = −0.153 cm-1, g = 2.07), which is correlated by the magnetic pathway to the corresponding structure