Bidentate Linkage Research Articles

Construction of Cobalt-Containing Polyoxovanadate-Based Inorganic-Organic Hybrids as Heterogeneous Catalysts for the Selective Oxidation of Sulfides.

In order to develop efficient catalysts for the selective oxidation of sulfides, in this work, two polyoxovanadate-based inorganic-organic hybrids, [Co(H2O)3(3-bpfb)0.5(V2O6)]·(3-bpfb)0.5 (1) and [Co(H2O)2(4-bpfb)0.5(V2O6)] (2) [3-bpfb = N, N'-bis(3-pyridylformamide)-1, 4-benzenediamine, 4-bpfb = N, N'-bis(4-pyridylformamide)-1, 4-benzenediamine], were isolated under hydrothermal conditions. The structures of 1 and 2 embodied two kinds of different cobalt-containing polyoxovanadate-based inorganic chains. Compound 1 contained a one-dimensional inorganic zigzag chain created by the aggregation of {V2O6} clusters with each other, on which Co (II) ions were fixed. But it was an inorganic dimeric chain constructed from two linear {V2O6} cluster-based chains gathered by Co (II) ions in 2. The 3-bpfb and 4-bpfb ligands, as the bidentate linkers, coordinated with two Co (II) ions from adjacent chains to organize them into two-dimensional layers. The hydrogen bonds made important contributions to the formation of supramolecular structures of the two compounds. The two compounds served as heterogeneous catalysts and exhibited efficient activity for the selective oxidation of sulfide to sulfoxide and could be reused at least six times without loss of catalytic activity and stability.

Comparison of Electrical Conductivity and Schottky Behavior of 4‐[2‐(9‐anthryl)vinyl]pyridine Based Two 1D Coordination Polymers of Zn(II) and Cd(II)

AbstractWith the increase in demand of electronic devices in the modern civilization, research in material science is being projected to grow in faster rate. In this facet, coordination polymer (CP) based electronic device is one of the promising candidates to the material researchers. Herein, two new Zn(II) and Cd(II) based one‐dimensional (1D) CPs, denoted as [Zn(4‐avp)2(5‐nip)] ⋅ (solvent)x (1) and [Cd(4‐avp)(5‐nip)(CH3OH)] (2) have been synthesized using relatively less explored highly conjugated polycyclic aromatic hydrocarbon (PAH) based monodentate ligand, 4‐[2‐(9‐anthryl)vinyl]pyridine (4‐avp) and bidentate linker 5‐nitroisophthalic acid (H25‐nip). In this instance, the CP 1 creates 1D chain polymer, while CP 2 is made up with 1D ladder polymer. It is interesting to note that both the CPs exhibit semiconducting nature and generate metal‐semiconductor (MS) junction Schottky barrier diodes (SBDs). However, Cd‐based CP 2 shows higher charge transport as compared to Zn‐CP 1, which could be due to stronger π⋅⋅⋅π contacts as well as larger size of Cd metal in CP 2. The experimental results are well corroborated with theoretical density of states (DOS) calculations.

Two 2D inorganic—organic hybrid compounds containing Anderson—type polyoxometalate for electrocatalytic and capacitive performances

For constructing the compounds containing polyoxometalate with electrochemical properties, to employ 3,5 − di − [1,2,4]triazol − 1 − yl − benzonitrile (DTCN) as organic ligand, Anderson − type polyoxometalate {TeMo6O24}6− as inorganic building block, two inorganic–organic hybrid compounds were synthesized under hydrothermal condition, formulated as {M(H2O)4(DTCN)2}[M2(H2O)2(DTCN)2{TeMo6O24}]·2H2O [M = Co (1), Ni (2)]. Structural analysis indicated that two compounds have 2D structures. The {TeMo6O24}6− polyoxoanions were each other aggregated through paired transition metal centers to generate a 1D inorganic chain. The DTCN ligand played a role of bidentate linker, utilizing the nitrogen atoms of two triazole groups to link these inorganic chains into a 2D grid − like layer. Another kind of metal − organic fragments {M(H2O)4(DTCN)2}2+ were arranged in the grids. Compounds 1 and 2 displayed not only electrocatalytic activities for the reduction of Cr(VI), but also sensing activities with the limit of detection of 0.011 μM for 1 and 0.019 μM for 2, as well as capacitive performances with specific capacitances of 1297F·g−1 for 1 and 968F·g−1 for 2 at a current density of 1 A·g−1. The results might provide a potential approach for preparing polyoxometalate − based inorganic–organic hybrid compounds used as electrochemical materials.

Palladium(ii)-catalyzed intramolecular C–H amination to carbazole: the crucial role of cyclic diacyl peroxides

Herein, we have developed an efficient PdII-catalyzed intramolecular oxidative C–H amination under additive-free and green conditions where strained cyclic diacyl peroxide functions as both a sacrificial oxidant and a bidentate linker.

A Foldable Metal–Organic Framework with cds Topology Assembled via Four-Connected Square-Planar Single Ni2+-Ion Nodes and Linear Bidentate Linkers

A binary, three-dimensional (3D), foldable, Metal–Organic Framework (MOF) of formula {[trans-Ni(H2O)2(μ-4,4′-bpy)2](ClO4)2}n (1), with CdSO4 (65 8), cds, topology, based on four-connected (4-c) square-planar single Ni2+ ion nodes and two-connected (2-c) linear rigid 4,4′-bipyridine (4,4′-bpy) ligands, was synthesized and structurally characterized via single crystal X-ray crystallography. The 41° dihedral angle between two distinct coordination environments within the 3D network of 1 produced the self-dual topology of Ni2+ nodes. Two rectangular 1D channels ran parallel to the crystallographic a-axis and b-axis, respectively, creating a 44.2% volume porosity, probed by gas (N2, CO2, and H2) sorption studies. The PXRD, FT-IR, Raman, EDS, and SEM methods were employed for the study of 1. A thermogravimetric analysis (TGA) showed that coordinated water molecules were readily removed upon heating, whereas the 3D lattice remained intact up to 370 °C.

Performance enhancement of PbS quantum dot solar cells employing a hybrid solid-state ligand exchange protocol

In this work, a hybrid (HB) solid-state ligand exchange strategy was developed for PbS quantum dots (QDs) films, incorporating a synergistic utilization of the popular inorganic ligand tetrabutylammonium iodide (TBAI) and the organic short bidentate linker 1, 2-Ethanedithiol (EDT) in a two-stage process. The two-stage process consisted of a primary solid-state ligand treatment with TBAI in a controlled manner followed by a second-stage ligand treatment with EDT. We could achieve an optimal iodine/EDT ligand passivation ratio for the QDs films by controlling the TBAI ligand treatment time. The method integrates the benefits of both the ligands and resolves the intrinsic incompleteness of the solid-state TBAI ligand exchange. The QDs films thus created have an optimal surface coverage and reduced inter-dot spacing due to an improved QDs close packing. This in turn led to lesser recombination routes due to reduced mid-bandgap trap states and an improved charge transport property through an enhanced electronic coupling between the QDs. A power conversion efficiency of 8.2 % has been achieved in the device with an optimized TBAI /EDT ligand passivation ratio for the QDs films with an EDT hole transport layer.

Directional Shunting of Photogenerated Carriers in POM@MOF for Promoting Nitrogen Adsorption and Oxidation.

The efficient catalysis of nitrogen (N2 ) into high-value N-containing products plays a crucial role in the N economic cycle. However, weak N2 adsorption and invalid N2 activation remain two major bottlenecks in rate-determining steps, leading to low N2 fixation performance. Herein, an effective dual active sites photocatalyst of polyoxometalates (POMs)-based metal-organic frameworks (MOFs) is highlighted via altering coordination microenvironment and inducing directional shunting of photogenerated carriers to facilitate N2 /catalyst interaction and enhance oxidation performance. MOFs create more open unsaturated metal cluster sites with unoccupied d orbital possessing Lewis acidity to accept electrons from the 3σg bonding orbital of N2 for storage by combining with POMs to replace bidentate linkers. POMs act as electron sponges donating electrons to MOFs, while the holes directional flow to POMs. The hole-rich POMs with strong oxidation capacity are easily involved in oxidizing adsorbed N2 . Taking UiO-66 (C48 H28 O32 Zr6 ) and Mo72 Fe30 ([Mo72 Fe30 O252 (CH3 COO)12 {Mo2 O7 (H2 O)}2 {H2 Mo2 O8 (H2 O)}(H2 O)91 ]·150H2 O) as an example, Mo72 Fe30 @UiO-66 shows twofold enhanced adsorption of N2 (250.5cm3 g-1 ) than UiO-66 (122.9cm3 g-1 ) at P/P0 =1. And, the HNO3 yield of Mo72 Fe30 @UiO-66 is 702.4µgg-1 h-1 , ≈7times and 24 times higher than UiO-66 and Mo72 Fe30 . This work provides reliable value for the storage and relaying artificial N2 fixation.

Unprecedented Coordination Compounds with 4,4′-Diaminodiphenylethane as a Supramolecular Agent and Ditopic Ligand: Synthesis, Crystal Structures and Hirshfeld Surface Analysis

In this pioneering research, mononuclear coordination complexes and coordination polymers were obtained using the conformationally flexible ditopic ligand 4,4′-diaminodiphenylethane and different metal salts (nitrates, sulfates, tetrafluoroborates and perchlorates). Seven new products, including the mononuclear complexes [Cd(2,2′-bpy)3](ClO4)2](dadpe)(4,4′-bpy) (1), [Ni(dadpe)2(H2O)4](SO4).H2O (2), one-dimensional coordination polymers {[Zn(NO3)(dadpe)(dmf)2](NO3)}n (3), {[Cd(2,2′-bpy)2(dadpe)](ClO4)2}n (4), and two-dimensional coordination polymers, {[Cd(4,4′-bpy)2(H2O)2](ClO4)2(dadpe)(EtOH)2}n (5), {[Co(4,4′-bpy)2(H2O)2](BF4)2(dadpe)(EtOH)2}n (6) and {[Cd(adi)(dadpe)](H2adi)}n (7), (dadpe=4,4′-diaminodiphenylethane, 2,2′-bpy=2,2′-bipyridine, 4,4′-bpy=4,4′-bipyridine, H2adi=adipic acid) were produced. The synthesized compounds were characterized by FTIR and single-crystal X-ray diffraction analyses. The dadpe was recorded as a neutral guest in the crystals of mononuclear complex 1 and in coordination polymers 5 and 6. In compound 2, two dadpe ligands coordinate in a monodentate mode and occupy two trans-positions in the [Ni(H2O)4(dadpe)2]2+ octahedral complex cation. Coordination polymers 3 and 4 represent single chains originating from dadpe as a bidentate linker in both. The H-donor’s possibilities of amino groups were utilized in the interconnection of coordination chains into H-bonded networks via NH(NH2)···O hydrogen bonds. The isostructural coordination polymers 5 and 6 comprise similar cationic square grids [M(4,4′-bpy)2(H2O)2]2+ [M=Cd (5), M=Co (6)], with sql topology balanced by the charge-compensated anions, while dadpe and EtOH as neutral guests are situated in the interlayer space. The neutral 2D coordination network in 7 with the sql topology originates from both adi and dadpe linkers as bidentate-bridging ligands, and the neutral H2adi is entrapped as a guest in crystal lattice. The impact of different types of intermolecular interactions was evaluated by Hirshfeld surface analysis.

Immobilization of L-ribose isomerase on the surface of activated mesoporous MCM41 and SBA15 for the synthesis of L-ribose

A hexagonal mesoporous molecular sieve-like structure of MCM41 and SBA15 with a large surface area was used to immobilize protein L-ribose isomerase (L-RI) through covalent linkages. The amino group of APTES functionalized nanosilica support MCM41 and SBA15 interacted with glutaraldehyde to promote bidentate linkage and on other side with amino group of enzyme. The use of mesoporous silica matrix for immobilization was observed to conserve the distinctive properties of the protein. The various operational conditions optimized for covalent conjugation of protein with the silica support were found to be dependent on enzyme support ratio, immobilization temperature and time. The immobilization yield of L-RI on MCM41 and SBA15 was achieved to be 60 % (600 mg enzyme /g matrix) and 45 % (450 mg enzyme/g matrix), respectively under the optimized conditions. The immobilized biocatalyst was characterized by various analytical techniques like HR-TEM, EDS, FTIR, TGA and BET. Effects of different experimental conditions were optimized to study enzyme kinetics, pH, temperature, bioconversion, reusability, metal ion effect and storage stability. The biocatalytic efficiency (kcat/Km) was increased by 1.2 fold on immobilization with the catalytic activity of 39.64 IU. Increase in the catalytic efficiency after immobilization could be due to the suitable orientation of enzyme active site and improved accessibility for substrate binding. The immobilization of L-RI on mesoporous silica support could improve the biocatalytic activity, storage stability and reusability. The immobilized biocatalyst was found to be reusable for more than 4 cycles retaining more than 50 % of catalytic activity and promoting the synthesis of a rare sugar L-ribose from L-ribulose with a conversion yield of 22 % in 2 h time.

Linker Engineering of Ligand-Decorated DNA Origami Nanostructures Affects Biological Activity.

News from an old acquaintance: The streptavidin (STV)-biotin binding system is frequently used for the decoration of DNA origami nanostructures (DON) to study biological systems. Here, a surprisingly high dynamic of the STV/DON interaction is reported, which is affected by the structure of the DNA linker system. Analysis of different mono- or bi-dentate linker architectures on DON with a novel high-speed atomic force microscope (HS-AFM) enabling acquisition times as short as 50ms per frame gave detailed insights into the dynamics of the DON/STV interaction, revealing dwell times in the sub-100millisecond range. The linker systems are also used to present biotinylated epidermal growth factor on DON to study the activation of the epidermal growth factor receptor signaling cascade in HeLa cells. The studies confirm that cellular activation correlated with the binding properties of linker-specific STV/DON interactions observed by HS-AFM. This work sheds more light on the commonly used STV/DON system and will help to further standardize the use of DNA nanostructures for the study of biological processes.

Linker Scissoring Strategy Enables Precise Shaping of Metal–Organic Frameworks for Chromatographic Separation

AbstractPrecise shaping of metal–organic frameworks (MOFs) is significant in both fundamental coordination chemistry and practical applications, such as catalysis, separation, and biomedicine. Herein, we demonstrated a linker scissoring strategy for precisely shaping MOFs through surface conformational pairing. In this strategy, the bidentate linkers which were designed according to the original tetratopic ligands and the coordination environment of MOF surfaces, were utilized as the covering agents. The shape of these covering agents and the surface conformation of metals onto MOFs restricted them to coordinate on specific MOF facets thus precisely controlling the shape of the MOFs. Different shapes of PCN‐608 from nanoplate (PCN‐NP) to nanorod (PCN‐NR) have been targeted by adding different bidentate linkers. The universality of this strategy was demonstrated by controlling the shapes of the NU‐MOFs from nanoplate to nanorod. This strategy provides a new guiding principle to synthesize MOF nanocrystals with controlled shapes.

Linker Scissoring Strategy Enables Precise Shaping of Metal-Organic Frameworks for Chromatographic Separation.

Precise shaping of metal-organic frameworks (MOFs) is significant in both fundamental coordination chemistry and practical applications, such as catalysis, separation, and biomedicine. Herein, we demonstrated a linker scissoring strategy for precisely shaping MOFs through surface conformational pairing. In this strategy, the bidentate linkers which were designed according to the original tetratopic ligands and the coordination environment of MOF surfaces, were utilized as the covering agents. The shape of these covering agents and the surface conformation of metals onto MOFs restricted them to coordinate on specific MOF facets thus precisely controlling the shape of the MOFs. Different shapes of PCN-608 from nanoplate (PCN-NP) to nanorod (PCN-NR) have been targeted by adding different bidentate linkers. The universality of this strategy was demonstrated by controlling the shapes of the NU-MOFs from nanoplate to nanorod. This strategy provides a new guiding principle to synthesize MOF nanocrystals with controlled shapes.

Synthesis and catalytic application of a curcumin‐based bio‐MOF in one‐pot preparation of tetrahydroquinazolinone derivatives via Biginelli reaction

AbstractIn this work, a new curcumin‐based bidentate linker ligand, CurOAc, including two –COO−moieties at positions‐4 in phenyl rings, was designed, synthesized, and characterized. Accordingly, its corresponding zinc‐organic framework, Zn‐CurOAc, as a bio‐metal–organic framework (MOF) has been prepared and evaluated in the one‐pot three‐component Biginelli condensation reaction of substituted aromatic aldehydes, urea, and dimedone in ethanol. Zn‐CurOAc shows an excellent catalytic performance for the synthesis of tetrahydroquinazolinone derivatives at room temperature with high turnover frequency (TOF) values (5.43–10.86 h−1). The chemical structure of Zn‐CurOAc was characterized by fourier‐transform infrared spectroscopy (FT‐IR), X‐ray diffraction (XRD), inductively coupled plasma optical emission spectrometry (ICP‐OES), field emission‐scanning electron microscopy (FE‐SEM), transmission electron microscope (TEM), energy dispersive X‐ray (EDX), differential thermal analysis (DTA), and thermogravimetric analysis (TGA) techniques. This new catalytic approach was proceeded by the excellent isolated yields, short reaction times, and easy workup.

Assembly of Chiral Cluster-Based Metal-Organic Frameworks and the Chirality Memory Effect during their Disassembly.

Many metal clusters are intrinsically chiral but are often synthesized as a racemic mixture. By taking chiral Ag14(SPh(CF3)2)12(PPh3)4(DMF)4 (Ag14) clusters with bulky thiolate ligands as an example, we demonstrate herein an interesting assembly disassembly (ASDS) strategy to obtain the corresponding, optically pure crystals of both homochiral enantiomers, R-Ag14m and S-Ag14m. The ASDS strategy makes use of two bidentate linkers with different chiral configurations, namely, (1R,2R,N1E,N2E)-N1,N2-bis(pyridin-3-ylmethylene)cyclohexane-1,2-diamine (LR) and the corresponding chiral analogue LS. For comparison, we also use the racemic mixture of equimolar of LR and LS (LRS). Three three-dimensional (3D) Ag14-based metal-organic frameworks (MOFs) were characterized by X-ray crystallography to be [Ag14(SPh(CF3)2)12(PPh3)4(LR)2]n (Ag14-LR), [Ag14(SPh(CF3)2)12(PPh3)4(LS)2]n (Ag14-LS), and [Ag14(SPh(CF3)2)12(PPh3)4(LRS)2]n (Ag14-LRS), respectively. As expected, the building blocks in Ag14-LR or Ag14-LS are homochiral R-Ag14 or S-Ag14, respectively. In contrast, Ag14-LRS is achiral and crystallizes with a diamond-like structure containing alternate R-Ag14 and S-Ag14 clusters. During the assembly process, the racemic Ag14 clusters were converted to homochiral building blocks, namely, R-Ag14 for Ag14-LR and S-Ag14 for Ag14-LS. Subsequently, the chiral linkers were removed from the crystals of Ag14-LR and Ag14-LS via hydrolysis with water, and from the disassembled solid material Ag14-DR and Ag14-DS, optically pure enantiomers R-Ag14m and S-Ag14m were obtained. It is hoped that this simple assembly strategy can be used to construct cluster-based chiral assemblage materials and that the subsequent disassembly protocol can be used to obtain optically pure chiral cluster molecules from as-prepared racemic mixtures.

DFT and TD-DFT Investigation of a Charge Transfer Surface Resonance Raman Model of N3 Dye Bound to a Small TiO2 Nanoparticle

Raman spectroscopy is an important method for studying the configuration of Ru bipyridyl dyes on TiO2. We studied the [Ru(II)(4,4′-COOH-2,2′-bpy)2(NCS)2)] dye (N3) adsorbed on a (TiO2)5 nanoparticle using Density Functional Theory, DFT, to optimize the geometry of the complex and to simulate normal Raman scattering, NRS, for the isolated N3 and the N3–(TiO2)5 complex. Two configurations of N3 are found on the surface both anchored with a carboxylate bridging bidentate linkage but one with the two NCS ligands directed away from the surface and one with one NSC tilted away and the other NCS interacting with the surface. Both configurations also had another –COOH group hydrogen bonded to a Ti-O dangling bond. These configurations can be distinguished from each other by Raman bands at 2104 and 2165 cm−1. The former configuration has more intense Normal Raman Scattering, NRS, on TiO2 surfaces and was studied with Time-Dependent Density Functional Theory, TD-DFT, frequency-dependent Raman simulations. Pre-resonance Raman spectra were simulated for a Metal to Ligand Charge Transfer, MLCT, excited state and for a long-distance CT transition from N3 directly to (TiO2)5. Enhancement factors for the MLCT and long-distance CT processes are around 1 × 103 and 2 × 102, respectively. A Herzberg–Teller intensity borrowing mechanism is implicated in the latter and provides a possible mechanism for the photo-injection of electrons to titania surfaces.

2D‐Coordination Polymers Constituted from Indium Halides and Dipyridyl N‐Donor Ligands

AbstractFour indium‐based, 2D coordination polymers (CP) were synthesized utilizing InCl3 and InI3 and the bidentate ligands 4,4’‐bipyridine (bipy), 1,2‐di(4‐pyridyl)ethylene (bpe) and 1,2‐di(4‐pyridyl)ethane (bpa). The isoreticular networks [In2Cl6(bipy)] (1) and [In2Cl6(bpe)] (2) are constituted by chloride‐ and ligand‐bridged octahedra with a honeycomb like (6,3)‐net topology (hcb topology). In contrast, [(In4Cl12)(bpa)3] (3) consists of {In4Cl12N6} units, with each indium atom being coordinated by chloride anions and bpa ligands in an octahedral fashion. Bpa ligands connect indium atoms in two dimensions, forming a semi‐regular uninodal 3‐c net with the point symbol (4,82), as present in the fes topology. In [(InI3)2(bpa)3] (4), indium is coordinated by three iodide and three bpa ligands in a meridional fashion. In contrast to [In2Cl6(bipy)] (1) and [In2Cl6(bpe)] (2), the indium‐centered octahedra are linked by the bidentate linker only, but also a honeycomb‐like, zigzag‐shaped (6,3)‐net with a hcb topology is formed. The CPs were investigated by SCXRD, PXRD, IR‐spectroscopy, and with DTA/TG regarding their thermal properties.

Group 13 Metal Halide Based Coordination Polymers of Al, Ga, In and 2,4,6‐Tri(4‐pyridyl)‐1,3,5‐triazine

Four isotypic one‐dimensional coordination polymers (CP) were synthesized using the group 13 metal halides AlBr3, GaCl3, GaBr3, and InI3 and the tridentate ligand 2,4,6‐tri(4‐pyridyl)‐1,3,5‐triazine (tpt) serving as bidentate linker. The neutral one‐dimensional CPs 1∞[AlBr3(tpt)], 1∞[GaCl3(tpt)], 1∞[GaBr3(tpt)], and 1∞[InI3(tpt)] are constituted by zigzag‐shaped chains in the crystal structure, in which one coordination site of the tpt ligand remains uncoordinated. All CPs were characterized by SCXRD, PXRD, simultaneous DTA/TG, elemental‐analysis and IR spectroscopy. Furthermore, three complexes of the composition [(AlBr3)3(tpt)], [(GaCl3)3(tpt)], and [(GaBr3)3(tpt)] were structurally characterized by SCXRD, being preliminary and side products of the formation of the coordination polymers.

Bidentate carboxylate linked TiO2 with NH2-MIL-101(Fe) photocatalyst: a conjugation effect platform for high photocatalytic activity under visible light irradiation

Interfacial conjugation was employed to engineering preparation of TiO2@NH2-MIL-101(Fe) heterojunction photocataysts through carboxylate bidentate linkage with TiO2 and NH2-MIL-101(Fe), which can enhance the electron transfer capability from metal-organic frameworks (MOFs) to TiO2 and photocatalytic activity. The carbon nanospheres derived from glucose act as reducing agent and template to synthesize oxygen vacancies TiO2 hollow nanospheres. Then, the oxygen vacancies were employed as antennas to connect 2-aminoterephtalic acid as bidentate carboxylate chelating linkage on TiO2, which have been proved by the density functional theory (DFT) calculations. Subsequently, NH2-MIL-101(Fe) was coordinatingly formed on the surface of TiO2. The conjugation effects between TiO2 and NH2-MIL-101(Fe) enhanced the electron transfer capability and could also induce the band tail states to narrow bandgap of the composites. Thus, the photodegradability of methylene blue was remarkably enhanced under visible light irradiation. The degradation rate of TiO2@17%NH2-MIL-101(Fe) was 0.131 min−1, which was about 3.5 and 65 times higher than that of NH2-MIL-101(Fe) and TiO2, respectively.

Tuned Hydrogen Bonding in Rare-Earth Metal-Organic Frameworks for Design of Optical and Electronic Properties: An Exemplar Study of Y-2,5-Dihydroxyterephthalic Acid.

Organic linkers in metal-organic framework (MOF) materials exhibit differences in hydrogen bonding (H-bonding), which can alter the geometric, electronic, and optical properties of the MOF. Density functional theory (DFT) simulations were performed on a photoluminescent Y-2,5-dihydroxyterephthalic acid (DOBDC) MOF with H-bonding concentrations between 0 and 100%; the H-bonds were located on both bidentate- and monodentate-bound DOBDC linkers. At 0% H-bond concentration in the framework, the lattice parameters contracted, the density increased, and simulated X-ray diffraction patterns shifted. Comparison with published experimental data identified that Y-DOBDC MOF structures must have a degree of H-bond concentration. The concentration of H-bonds in the system shifted the calculated band gap energy from 2.25 eV at 100% to 3.00 eV at 0%. The band gap energies also indicate a distinction of H-bonds formed on bidentate-coordinated linkers compared to those on monodentate linkers. Additionally, when the calculated optical spectra are compared with experimental data, the ligand-to-ligand charge-transfer luminescence in Y-DOBDC MOFs is expected to result from an average of 20-40% H-bonding with at least 50% of the bidentate linkers containing H-bonding. Therefore, the type of H-bonding within the DOBDC linker determines the electronic structure and the optical absorption of the MOF framework structure. Tuning of the H-bonding in rare-earth MOFs provides an opportunity to control the specific optical and adsorption properties of the MOF framework on the basis of reactions between the linker and the environment.

Interplay of Tri- and Bidentate Linkers to Evolve Micropore Environment in a Family of Quasi-3D and 3D Porous Coordination Polymers for Highly Selective CO2 Capture.

In the design and construction of porous materials, these with exceptional structure and composition are often highly expected, as they may offer unique nanopore space for desired applications. Here, a new family of quasi-3D and a 3D porous coordination polymers (PCPs) (termed NTU-43 to NTU-50) were constructed via an evolution strategy from a layered structure (termed NTU-42). Single gas adsorption isotherms of CO2, N2, and CH4 display the dependency of gas capacity on optimized effects of pore size, functionality, and charged framework of these quasi-3D PCPs, where NTU-45 and NTU-46, the two with NH2-BDC and OH-BDC bidentate linkers (NH2-BDC = 2-aminoterephthalic acid and OH-BDC = 2-hydroxyterephthalic acid) have demonstrated outstanding ability for selective CO2 uptake. To the best of our knowledge, this is the first time to well explore the synergistic effects toward gas adsorption on a platform of quasi-3D frameworks. More importantly, the efficient CO2 capture from CO2/CH4 and CO2/N2 mixtures has been also validated by breakthrough experiments under continuous and dynamic conditions at 298 K.