Water vapour sorption properties of a family of square lattice topology porous coordination networks.

Porous coordination networks (PCNs) such as metal-organic frameworks are of topical interest thanks to their potential utility as sorbents for gas and vapour separations and/or storage. Interpenetrated PCNs, some of which offer promise for gas separations, remain relatively understudied in the context of water vapour sorption. Herein, we report an in-depth study of the water vapour sorption properties of a family of square lattice topology () PCNs of general formula (, M = Mn, Co, Ni, Zn, bipy = 4,4-bipyridine, squa = squarate).

A Diazo Linker Ligand Promotes Flexibility and Induced Fit Binding in a Microporous Copper Coordination Network.

Flexible organic linkers represent an intuitive and effective strategy to design flexible metal-organic materials. We report herein a systematic study concerning the effect of varying the central bond of mixed pyridyl-benzoate linkers, L, upon the flexibility of three isostructural kdd topology microporous coordination networks (CNs) of formula ML: X-kdd-1-Cu, 1 = L = (E)-4-(pyridin-4-yldiazenyl)benzoate; X-kdd-2-Cu, 2 = L = (E)-4-(2-(pyridin-4-yl)vinyl)benzoate; the previously reported X-kdd-3-Cu, 3 = L = 4-(pyridin-4-ylethynyl)benzoate. As revealed by single crystal x-ray diffraction (SCXRD) and gas sorption studies, X-kdd-1-Cu, exhibited gate-opening during CO and hydrocarbon (C2 and C8) sorption experiments whereas the other two CNs did not.

A pcu topology metal-organic framework, Ni(1,4-bib)(inca), that exhibits high CO/N selectivity and low water vapour affinity.

Herein we report the synthesis of a new metal-organic framework, Ni(1,4-bib)(inca) or pcu-1-Ni, where 1,4-bib = 1,4-bis(imidazole-1-yl)benzene, inca = indazole-5-carboxylic acid, through the crystal engineering strategy of using an N-donor linker to pillar a square lattice, sql, topology net. pcu-1-Ni adopts pcu topology and features two types of hydrophobic pore, small pore A and large pore B. The biporous nature of pcu-1-Ni is reflected in its stepped CO and HO adsorption isotherms, highlighting the influence of pore size and chemistry on gas and water vapour sorption properties.

One Step Further: A Flexible Metal-Organic Framework that Functions as a Dual-Purpose Water Vapor Sorbent.

We report a water induced phase transformation in a flexible MOF, [Zn(OH)(btca)] (Hbtca = 1H-benzotriazole-5-carboxylic acid), that exhibits a two-step water vapor sorption isotherm associated with water-induced phase transformations. Variable temperature X-ray diffraction studies revealed that the dehydrated phase, LP-β, is almost isostructural with the previously reported solvated phase, LP-α. LP-β reversibly transformed to a partially hydrated phase, NP, at 5% RH, and a fully hydrated phase, LP-γ, at 47% RH.

An Ultramicroporous Physisorbent Sustained by a Trifecta of Directional Supramolecular Interactions.

2D and 3D porous coordination networks (PCNs) as exemplified by metal-organic frameworks, MOFs, have garnered interest for their potential utility as sorbents for molecular separations and storage. The inherent modularity of PCNs has enabled the development of crystal engineering strategies for systematic fine-tuning of pore size and chemistry in families of related PCNs. The same cannot be said about one-dimensional (1D) coordination polymers, CPs, which are understudied with respect to porosity.

Crystal engineering of a new platform of hybrid ultramicroporous materials and their CH/CO separation properties.

Hybrid ultramicroporous materials (HUMs) comprised of combinations of organic and inorganic linker ligands are a leading class of physisorbents for trace separations involving C1, C2 and C3 gases. First generation HUMs are modular in nature since they can be self-assembled from transition metal cations, ditopic linkers and inorganic "pillars", as exemplified by the prototypal variant, SIFSIX-3-Zn (3 = pyrazine, SIFSIX = SiF ). Conversely, HUMs that utilise chelating ligands such as ethylenediamine derivatives are yet to be explored as sorbents.

Modulation of Water Vapor Sorption by Pore Engineering in Isostructural Square Lattice Topology Coordination Networks.

We report a crystal-engineering study conducted upon a platform of three mixed-linker square lattice () coordination networks of general formula [Zn(Ria)(bphy)] [bphy = 1,2-bis(pyridin-4-yl)hydrazine, HRia = 5-position-substituted isophthalic acid, and R = -Br, -NO, and -OH; compounds -]. Analysis of single-crystal X-ray diffraction data of - and the simulated crystal structure of revealed that - are isomorphous and sustained by bilayers of networks linked by hydrogen bonds. Although similar pore shapes and sizes exist in -, distinct isotherm shapes (linear and S shape) and uptakes (2.

Effect of Polymorphism on the Sorption Properties of a Flexible Square-Lattice Topology Coordination Network.

The stimulus-responsive behavior of coordination networks (CNs), which switch between closed (nonporous) and open (porous) phases, is of interest because of its potential utility in gas storage and separation. Herein, we report two polymorphs of a new square-lattice () topology CN, , of formula [Cu(Imibz)] (HImibz = {[4-(1-imidazol-1-yl)phenylimino]methyl}benzoic acid), isolated from the as-synthesized CN , which subsequently transformed to a narrow pore solvate, , upon mild activation (drying in air or heating at 333 K under nitrogen). contains MeOH in cavities, which was removed through exposure to vacuum for 2 h, yielding the nonporous (closed) phase .

Dinuclear Copper Sulfate-Based Square Lattice Topology Network with High Alkyne Selectivity.

Porous coordination networks (PCNs) sustained by inorganic anions that serve as linker ligands can offer high selectivity toward specific gases or vapors in gas mixtures. Such inorganic anions are best exemplified by electron-rich fluorinated anions, e.g.

Switching Adsorbent Layered Material that Enables Stepwise Capture of C Aromatics via Single-Crystal-to-Single-Crystal Transformations.

Separation of the C aromatic isomers, xylenes (PX, MX, and OX) and ethylbenzene (EB), is important to the petrochemical industry. Whereas physisorptive separation is an energy-efficient alternative to current processes, such as distillation, physisorbents do not generally exhibit strong C selectivity. Herein, we report the mixed-linker square lattice () coordination network [Zn(sba)(bis)]·DMF (, Hsba or = 4,4'-sulfonyldibenzoic acid, bis or = trans-4,4'-bis(1-imidazolyl)stilbene) and its C sorption properties.

Effect of Extra-Framework Anion Substitution on the Properties of a Chiral Crystalline Sponge.

Chiral metal-organic materials, CMOMs, are of interest as they can offer selective binding sites for chiral guests. Such binding sites can enable CMOMs to serve as chiral crystalline sponges (CCSs) to determine molecular structure and/or purify enantiomers. We recently reported on the chiral recognition properties of a homochiral cationic diamondoid, dia, network {[Ni(-IDEC)(bipy)(HO)][NO]} (-IDEC = -indoline-2-carboxylicate, bipy = 4,4'-bipyridine), .

Water vapour induced structural flexibility in a square lattice coordination network.

Herein, we introduce a new square lattice topology coordination network, sql-(1,3-bib)(ndc)-Ni, with three types of connection and detail its gas and vapour induced phase transformations. Exposure to humidity resulted in an S-shaped isotherm profile, suggesting potential utility of such materials as desiccants.

Supramolecular isomerism and structural flexibility in coordination networks sustained by cadmium rod building blocks.

Bifunctional N-donor carboxylate linkers generally afford and topology coordination networks of general formula ML that are based upon the MN(CO) molecular building block (MBB). Herein, we report on a new N-donor carboxylate linker, β-(3,4-pyridinedicarboximido)propionate (PyImPr), which afforded Cd(PyImPr) reaction of PyImPrH with Cd(acetate)·2HO. We observed that, depending upon whether Cd(PyImPr) was prepared by layering or solvothermal methods, 2D or 3D supramolecular isomers, respectively, of Cd(PyImPr) were isolated.

Crystal Engineering of a Chiral Crystalline Sponge That Enables Absolute Structure Determination and Enantiomeric Separation.

Chiral metal-organic materials (CMOMs), can offer molecular binding sites that mimic the enantioselectivity exhibited by biomolecules and are amenable to systematic fine-tuning of structure and properties. Herein, we report that the reaction of Ni(NO), -indoline-2-carboxylic acid (-IDECH), and 4,4'-bipyridine (bipy) afforded a homochiral cationic diamondoid, , network, [Ni(-IDEC)(bipy)(HO)][NO], . Composed of rod building blocks (RBBs) cross-linked by bipy linkers, the activated form of adapted its pore structure to bind four guest molecules, 1-phenyl-1-butanol (1P1B), 4-phenyl-2-butanol (4P2B), 1-(4-methoxyphenyl)ethanol (MPE), and methyl mandelate (MM), making it an example of a chiral crystalline sponge (CCS).

Control over Phase Transformations in a Family of Flexible Double Diamondoid Coordination Networks through Linker Ligand Substitution.

In this work, we present the first metal-organic framework (MOF) platform with a self-penetrated double diamondoid () topology that exhibits switching between closed (nonporous) and open (porous) phases induced by exposure to gases. A crystal engineering strategy, linker ligand substitution, was used to control gas sorption properties for CO and C3 gases. Specifically, bimbz (1,4-bis(imidazol-1-yl)benzene) in the coordination network ([Ni(bimbz)(bdc)(HO)], Hbdc = 1,4-benzenedicarboxylic acid) was replaced by bimpz (3,6-bis(imidazol-1-yl)pyridazine) in ([Ni(bimpz)(bdc)(HO)]).

One Atom Can Make All the Difference: Gas-Induced Phase Transformations in Bisimidazole-Linked Diamondoid Coordination Networks.

Coordination networks (CNs) that undergo gas-induced transformation from closed (nonporous) to open (porous) structures are of potential utility in gas storage applications, but their development is hindered by limited control over their switching mechanisms and pressures. In this work, we report two CNs, [Co(bimpy)(bdc)] () and [Co(bimbz)(bdc)] () (Hbdc = 1,4-benzendicarboxylic acid; bimpy = 2,5-bis(1H-imidazole-1-yl)pyridine; bimbz = 1,4-bis(1H-imidazole-1-yl)benzene), that both undergo transformation from closed to isostructural open phases involving at least a 27% increase in cell volume. Although and only differ from one another by one atom in their -donor linkers (bimpy = pyridine, and bimbz = benzene), this results in different pore chemistry and switching mechanisms.

Structural Phase Transformations Induced by Guest Molecules in a Nickel-Based 2D Square Lattice Coordination Network.

Herein, we report the crystal structure and guest binding properties of a new two-dimensional (2D) square lattice () topology coordination network, , which is comprised of two linker ligands with diazene (azo) moieties, ()-1,2-di(pyridin-4-yl)diazene(azpy) and ()-5-(phenyldiazenyl)isophthallate(pdia). underwent guest-induced switching between a closed (nonporous) phase and several open (porous) phases, but unlike the clay-like layer expansion to distinct phases previously reported in switching networks, a continuum of phases was formed. In effect, exhibited elastic-like properties induced by adaptive guest binding.

A Robust Molecular Porous Material for C H /CO Separation.

A molecular porous material, MPM-2, comprised of cationic [Ni (AlF )(pzH) (H O) ] and anionic [Ni Al F (pzH) (H O) ] complexes that generate a charge-assisted hydrogen-bonded network with pcu topology is reported. The packing in MPM-2 is sustained by multiple interionic hydrogen bonding interactions that afford ultramicroporous channels between dense layers of anionic units. MPM-2 is found to exhibit excellent stability in water (>1 year).

Flexible Coordination Network Exhibiting Water Vapor-Induced Reversible Switching between Closed and Open Phases.

That physisorbents can reduce the energy footprint of water vapor capture and release has attracted interest because of potential applications such as moisture harvesting, dehumidification, and heat pumps. In this context, sorbents exhibiting an S-shaped single-step water sorption isotherm are desirable, most of which are structurally rigid sorbents that undergo pore-filling at low relative humidity (RH), ideally below 30% RH. Here, we report that a new flexible one-dimensional (1D) coordination network, [Cu(HQS)(TMBP)] (HHQS = 8-hydroxyquinoline-5-sulfonic acid and TMBP = 4,4'-trimethylenedipyridine), exhibits at least five phases: two as-synthesized open phases, α ⊃ HO and β ⊃ MeOH; an activated closed phase (γ); CO (δ ⊃ CO) and CH (ϵ ⊃ CH) loaded phases.

CO Capture by Hybrid Ultramicroporous TIFSIX-3-Ni under Humid Conditions Using Non-Equilibrium Cycling.

Although pyrazine-linked hybrid ultramicroporous materials (HUMs, pore size <7 Å) are benchmark physisorbents for trace carbon dioxide (CO ) capture under dry conditions, their affinity for water (H O) mitigates their carbon capture performance in humid conditions. Herein, we report on the co-adsorption of H O and CO by TIFSIX-3-Ni-a high CO affinity HUM-and find that slow H O sorption kinetics can enable CO uptake and release using shortened adsorption cycles with retention of ca. 90 % of dry CO uptake.

Improving Ethane/Ethylene Separation Performance under Humid Conditions by Spatially Modified Zeolitic Imidazolate Frameworks.

Gas separation performances are usually degraded under humid conditions for many crystalline porous materials because of the lack of water stability and/or the competition of water vapor toward the interaction sites (e.g., open metal sites).