Srinivasulu Parshamoni

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.

Tuning CO2 Uptake and Reversible Iodine Adsorption in Two Isoreticular MOFs through Ligand Functionalization

The synthesis and characterization of two isoreticular metal-organic frameworks (MOFs), {[Cd(bdc)(4-bpmh)]}n⋅2 n(H2O) (1) and {[Cd(2-NH2bdc)(4-bpmh)]}n⋅2 n(H2O) (2) [bdc = benzene dicarboxylic acid; 2-NH2bdc = 2-amino benzene dicarboxylic acid; 4-bpmh = N,N-bis-pyridin-4-ylmethylene-hydrazine], are reported. Both compounds possess similar two-fold interpenetrated 3D frameworks bridged by dicarboxylates and a 4-bpmh linker. The 2D Cd-dicarboxylate layers are extended along the a-axis to form distorted square grids which are further pillared by 4-bpmh linkers to result in a 3D pillared-bilayer interpenetrated framework. Gas adsorption studies demonstrate that the amino-functionalized MOF 2 shows high selectivity for CO2 (8.4 wt % 273 K and 7.0 wt % 298 K) over CH4 , and the uptake amounts are almost double that of non-functional MOF 1. Iodine (I2 ) adsorption studies reveal that amino-functionalized MOF 2 exhibits a faster I2 adsorption rate and controlled delivery of I2 over the non-functionalized homolog 1.

A 2D coordination polymer based on Co3-SBU showing spin-canting ferromagnetic behaviour

A 2D MOF with the secondary building unit [Co3(CTC)6(Py)2(OH)2] is synthesized using the sodium salt of a flexible ligand, cis,cis-cyclohexane-1,3,5-tricarboxylate (Na-CTC), and a cobalt trimer ([Co3O(CH3COO)6(Py)3]·ClO4). Structural analysis shows that the complex crystallizes in the monoclinic space group P21/n and forms a 2D framework with channel sizes of 9.0 × 4.2 A2. Magnetic characterization shows spin-canting ferromagnetic behaviour at low temperatures. Frequency dependency for in-phase (χ′M) and out-of-phase (χ′′M) signals at low temperatures is observed from the AC measurements. The gas adsorption behaviour suggests selectivity towards CO2 over N2, and demonstrates enhancement of CO2 uptake (19–33 cm3 g−1) on lowering the temperature (273–195 K).

A family of three magnetic metal organic frameworks: their synthesis, structural, magnetic and vapour adsorption study

Three flexible metal–organic frameworks (MOFs) based on aldrithiol linker and pyromellitate ligand, namely, [Co(aldrithiol)(pyromellitate)0.5(H2O)2]n (1), [Ni2(aldrithiol)2(pyromellitate)(H2O)2]n·2n(C2H5OH)·11n(H2O) (2) and [Cu(aldrithiol)2(pyromellitate)]n·2n(H2O) (3) have been synthesized through slow diffusion technique and characterized by structural, magnetic and adsorption studies. Single crystal X-ray studies show that compounds 1 and 3 have two-dimensional layered structures, whereas compound 2 adopts a three-dimensional framework structure. The observed dimensionality change might be due to the different orientation of pyridine rings in the flexible aldrithiol linker and versatile bridging modes of the pyromellitate ligand. In 1 and 2, the pyromellitate ligand coordinates to the metal centre in a monodentate fashion {(κ1)-(κ1)-(κ1)-(κ1)-μ4} and in 3, it coordinates in {(κ1)-(κ1)-μ2} fashion. The magnetic properties of 1–3 were investigated in detail and show weak antiferromagnetic coupling among the metal centres. Vapour sorption studies reveal that compounds 1 and 3 show high methanol vapour uptake, whereas compound 2 shows a decent amount of H2O adsorption. The dehydrated frameworks of 1–3 regenerate the as-synthesized framework structures upon exposure to water vapour.

Selective CO2 adsorption in four zinc(II)-based metal organic frameworks constructed using a rigid N,N′-donor linker and various dicarboxylate ligands

Four new Zn(II)-based metal organic frameworks (MOFs), namely, [Zn(tdc)(4-bpmh)]n·n(H2O) (1), [Zn(2-NH2BDC)(4-bpmh)]n·n(EtOH) (2), [Zn(NDC)(4-bpmh)]n (3) and {[Zn(ADPA)(4-bpmh)(H2O)](ClO4)}n·n(MeOH) (4) (tdc = 2,5-thiophene dicarboxylic acid, 2-NH2BDC = 2-aminoterephthalic acid, NDC = 2,6-naphthalene dicarboxylic acid, ADPA = adipic acid, 4-bpmh = N,N-bis-pyridin-4-ylmethylene-hydrazine) have been synthesized through the slow diffusion technique using a 4-bpmh linker and different dicarboxylic acids. Structural analysis reveals that compounds 1–3 have 3D networks with diamondoid (dia) topologies whereas compound 4 has a 2D pillared-trilayer framework with sql/Shubnikov tetragonal plane net topology. Compounds 1–2 have 6-fold interpenetrated nets and compound 3 is a 7-fold interpenetrated net. Gas adsorption studies reveal that all the compounds 1–4 show selective adsorption of CO2 over other gases (N2, CH4) at low temperature, and the uptake amount of compound 2 is almost double in comparison with those of compounds 1, 3 and 4.

Synthesis, characterisation, water adsorption and proton conductivity of three Cd( ii ) based luminescent metal–organic frameworks

Three hydrogen bonded three-dimensional (3D) metal–organic frameworks (MOFs) namely [Cd(L-tart)(bpy)(H2O)]n·9n(H2O) (1), [Cd(D-tart)(bpy)(H2O)]n·9n(H2O) (2) and [Cd(DL-tart)(bpy)(H2O)]n·6n(H2O) (3) (tart = tartaric acid, bpy = 4,4-bipyridine) have been synthesized by the solvent diffusion technique at room temperature. Compounds 1 and 2 have been characterized by single crystal X-ray analysis, whereas the powder X-ray diffraction patterns show that the structural integrity of compound 3 is similar to 1 and 2. Structural analysis of 1 and 2 shows H-bonded homochiral 3D MOFs, fabricated by the hydrogen bonding interactions between the nearby 2D pillared-layer frameworks through the metal-bound water, metal-bound carboxylate, free carboxylic acid and the hydroxy group of L-/D- tart. The absolute configuration of all the compounds was investigated by solid state circular dichroism (CD) spectroscopy, which signifies that 1 and 2 are enantiomers whereas 3 is racemic. The adsorption studies reveal that compounds 1–3 show a significant amount of uptake for water vapor (∼239 mL g−1 for 1, ∼240 mL g−1 in 2, whereas 184 mL g−1 for 3 at P/P0 ≈ 1 bar) over other solvents (MeOH, EtOH) and an impedance measurement indicates that these compounds show proton conduction (1.3 × 10−6 S cm−1 in 1, 1.3 × 10−6 S cm−1 in 2 and 4.5 × 10−7 S cm−1 in 3) at a higher temperature (358 K) and at 95% relative humidity. The observed conductivity is explained by the so-called vehicle mechanism (activation energy (Ea) = 0.63–0.77 eV). Since all the compounds contain H3O+ cations in the interlayer space, the hydronium ions might act as vehicles to transport the protons in the interlayer space. The photoluminescence properties of all the compounds are also reported.