Control of Channel Size for Selective Guest Inclusion with Inlaid Anionic Building Blocks in a Porous Cationic Metal-Organic Host Framework

Integrating Molecular Simulations with Machine Learning Guides in the Design and Synthesis of [BMIM][BF4]/MOF Composites for CO2/N2 Separation

Considering the existence of a large number and variety of metal-organic frameworks (MOFs) and ionic liquids (ILs), assessing the gas separation potential of all possible IL/MOF composites by purely experimental methods is not practical. In this work, we combined molecular simulations and machine learning (ML) algorithms to computationally design an IL/MOF composite. Molecular simulations were first performed to screen approximately 1000 different composites of 1-n-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF₄]) with a large variety of MOFs for CO₂ and N₂ adsorption. The results of simulations were used to develop ML models that can accurately predict the adsorption and separation performances of [BMIM][BF₄]/MOF composites. The most important features that affect the CO₂/N₂ selectivity of composites were extracted from ML and utilized to computationally generate an IL/MOF composite, [BMIM][BF₄]/UiO-66, which was not present in the original material data set. This composite was finally synthesized, characterized, and tested for CO₂/N₂ separation. Experimentally measured CO₂/N₂ selectivity of the [BMIM][BF₄]/UiO-66 composite matched well with the selectivity predicted by the ML model, and it was found to be comparable, if not higher than that of all previously synthesized [BMIM][BF₄]/MOF composites reported in the literature. Our proposed approach of combining molecular simulations with ML models will be highly useful to accurately predict the CO₂/N₂ separation performances of any [BMIM][BF₄]/MOF composite within seconds compared to the extensive time and effort requirements of purely experimental methods.

Modular Assembly of Isostructural Mixed-Ligand Uranyl Coordination Polymers Based on a Patterning Strategy

Controlling the orderly assembly of molecular building blocks for the formation of the desired architectural, chemical, and physical properties of the resulting solid-state materials remains a long-term goal and deserves to be examined. In this work, we propose a patterning strategy for modular assembly and structural regulation of mixed-ligand uranyl coordination polymers (CPs) through the combination of couples of organic ligands with complementary molecular geometry and well-matched coordination modes. By using a 5-(p-tolyldiazenyl)isophthalic acid ligand (H₂ptdi) with different rigid linear bicarboxylic acid linkers to construct a well-defined ladder-like pattern, five novel isostructural uranyl coordination polymers, [(UO)₂(ptdi)(bdc)_0.5](dma) (1), [(UO)₂(ptdi)(bpdc)_0.5](dma) (2), [(UO)₂(ptdi)(tpdc)_0.5](dma) (3), [(UO)₂(ptdi)(ndc)_0.5](dma) (4), and [(UO)₂(ptdi) (pdc)_0.5](dma) (5) {H₂bdc, 1,4-dicarboxybenzene; H₂bpdc, 4,4'-biphenyldicarboxylic acid; H₂tpdc, terphenyl-4,4″-dicarboxylic acid; H₂ndc, 2,6-naphthalenedicarboxylic acid; H₂pdc, 1,6-pyrenedicarboxylic acid; [dma]⁺, [(CH₃)₂NH₂]⁺}, were successfully synthesized. Structural analysis reveals that 1-5 have similar ladder-like units but different sizes of one-dimensional nanochannels and interlayer spacing due to the different lengths and widths of the linkers. Because of the changes in interlayer spacing of these isostructural cationic frameworks, differences in the performance of Eu³⁺ ion exchange with [dma]⁺ are observed. Moreover, those compounds with high phase purity have been further characterized by thermogravimetric analysis, infrared spectroscopy, and luminescence spectroscopy, element analysis, PXRD and UV spectroscopy. Among them, compound 3 with strong fluorescence can selectively detect Fe³⁺ over several competing metal cations in aqueous solution. This work not only provides a feasible patterning method for effectively regulating the modular synthesis of functional coordination polymers but also enriches the library of uranyl-based coordination polymers with intriguing structures and functionality.

A unique multi-functional cationic luminescent metal–organic nanotube for highly sensitive detection of dichromate and selective high capacity adsorption of Congo red

In this work a flexible multi-dentate 1-(4-aminobenzyl)-1,2,4-triazole (abtz) ligand has been employed, a unique cationic triazole–Ag(i) metal–organic nanotube {[Ag(μ₃-abtz)]·(NO₃)·(0.125H₂O)}_n (MONT-1) has been isolated under solvo-thermal conditions.

Triazole based Ag coordination clusters: synthesis, structural diversity and anion exchange properties

In this work three novel triazole based cluster-based silver(i) clusters have been isolated. 2 and 3 can effectively capturing the anion pollutants Cr₂O₇²⁻, MnO₄⁻ in water solutions and Congo Red in methanol solutions.

Syntheses, structures and luminescent properties of six divalent metal terephthalate coordination polymers based on three new flexible bis(imidazole) ligands

Six coordination polymers based on terephthalate and one of three bis(imidazole) ligands are reported.

The oriented and patterned growth of fluorescent metal-organic frameworks onto functionalized surfaces

A metal-organic framework (MOF) material, [Zn(2)(adc)(2)(dabco)] (adc = anthracene-9,10-dicarboxylate, dabco = 1,4-diazabicyclo[2.2.2]-octane), the fluorescence of which depends on the loading of its nanopores, was synthesized in two forms: as free-flowing nanocrystals with different shapes and as surface-attached MOFs (SURMOFs). For the latter, we used self-assembled monolayers (SAMs) bearing functional groups, such as carboxylate and pyridyl groups, capable of coordinating to the constituents of the MOF. It could be demonstrated that this directed coordination also orients the nanocrystals deposited at the surface. Using two different patterning methods, i.e., microcontact printing and electron-beam lithography, the lateral distribution of the functional groups could be determined in such a way that the highly localized deposition of the SURMOF films became possible.

catena-Poly[[[bis-(acetato-κ(2)O,O')aqua-cadmium]-μ-[(pyridin-3-yl)(pyridin-4-yl)methanone]-κ(2)N:N'] dihydrate]

In the title complex, {[Cd(CH₃COO)₂(C₁₁H₈N₂O)(H₂O)]·2H₂O}_n, the Cd^II ion adopts an O₅N₂ penta­gonal–bipyramidal coordination geometry with four acetate O atoms and one water O atom at the equatorial sites and two pyridine N atoms at the axial sites. The (pyridin-3-yl)(pyridin-4-yl)methanone ligand acts in a μ₂-bridging mode, linking the metal atoms, leading to an infinite chain along [-110]. O—H⋯O hydrogen bonds involving the lattice water mol­ecules connect these chains into a three-dimensional network.

Poly[[(μ(2)-di-3-pyridyl-methanone-κN:N')(μ(2)-hexa-fluoro-silicato-κF:F')copper(II)] dihydrate]

In the title complex, {[Cu(SiF(6))(C(11)H(8)N(2)O)(2)]·2H(2)O}(n), the Cu(II) atom adopts an N(4)F(2)-octa-hedral coordination geometry with four pyridine N atoms in the equatorial sites and two F atoms in the axial sites. The di-3-pyridyl-methanone and hexa-fluoro-silicate ligands act as bidentate ligands, linking symmetry-related Cu(II) atoms. Water mol-ecules form O-H⋯O and O-H⋯F hydrogen bonds with the di-3-pyridyl-methanone and hexa-fluoro-silicate ligands. The Cu(2+) and SiF(6) (2-) ions are each located on a twofold axis.

catena-Poly[(dichloridozinc)-μ-bis(pyridin-3-yl)methanone-κ2N:N′]

In the title polymer, [ZnCl₂(C₁₁H₈N₂O)]_n, the Zn^II atom lies on a twofold rotation axis and has a distorted tetra­hedral ZnCl₂N₂ geometry involving two chloride donors and two N-atom donors from μ₂-bridging bis­(pyridin-3-yl)methanone ligands, which also have twofold symmetry. A zigzag chain structure is formed, extending along (001). Each chain is surrounded by three others which are inter­connected through weak C=O⋯π_pyrid­yl [O⋯centroid = 2.999 (3) Å] and π_pyrid­yl–π_pyrid­yl inter­actions [minimum ring centroid separation = 4.014 (2) Å], giving a three-dimensional framework.

catena-Poly[[copper(II)-bis-[μ-bis-(pyridin-3-yl)methanone-κN:N']] bis-(tetra-fluorido-borate)]

In the title complex, {[Cu(C(11)H(8)N(2)O)(2)](BF(4))(2)}(n), the Cu(II) ion is situated on an inversion centre and adopts an N(4)F(2) octa-hedral coordination geometry with four N atoms from four different bis-(pyridin-3-yl)methanone ligands at the equatorial sites and two independent tetra-fluoridoborate anions weakly bonded at the axial sites via two F atoms [Cu⋯F = 2.613 (3) Å]. Chains with the bridging ligands are formed along the a axis. C-H⋯F inter-actions stabilize the structure. C-O⋯π inter-actions also occur.

catena-Poly[[(5-carb-oxy-2H-1,2,3-triazole-4-carboxyl-ato-κN,O)sodium]-di-μ-aqua-κO:O]

In the title coordination polymer, [Na(C₄H₂N₃O₄)(H₂O)₂]_n, the Na^I atom is six-coordinated by one O atom and one N atom from a 2H-1,2,3-triazole-4-carb­oxy-5-carboxyl­ate ligand and four O atoms from four water mol­ecules, forming a distorted octa­hedal geometry. The Na^I atoms are bridged by water mol­ecules into a chain structure along [100]. Inter­molecular N—H⋯O, O—H⋯N and O—H⋯O hydrogen bonds connect the chains. An intra­molecular O—H⋯O hydrogen bond between the carboxyl­ate groups is observed.