Supramolecular Framework Research Articles

Luminescent organic molecular frameworks from tetraphenylethylene-based building blocks

In this review, we mainly summarize the emerging luminescent organic molecular frameworks consisting of hydrogen bonded frameworks and supramolecular organic frameworks based on tetraphenylethylene building blocks.

Polypyridyl Ru(II) or cyclometalated Ir(III) functionalized architectures for photocatalysis.

The chemistry of polypyridyl Ru(II) and cyclometalated Ir(III) derivatives provides long-lasting interest to researchers due to the inherent advantage of their triplet states in a variety of photoactivities. The introduction of Ru(N^N)3 and Ir(C^N)2(X^N) modules into well-defined architectures extends the research areas of both photoactive metal complexes and network chemistry, generating a lot of new opportunities with interesting structural aesthetics and profound functional possibilities. The rapid development of research in integrating Ru(II) or Ir(III) metallotecons into the architectures has been apparent in recent years which makes this a fascinating subject for reviewing. This review focuses on the design and syntheses of Ru(N^N)3 and Ir(C^N)2(X^N) functionalized architectures of metal-organic frameworks (MOFs), covalent-organic frameworks (COFs), metallasupramolecules, organic supramolecules and supramolecular organic frameworks (SOFs). Furthermore, the photocatalytic applications including the hydrogen evolution reaction (HER), carbon dioxide reduction reaction (CO2RR), photocatalytic oxidation and photoredox catalysis of organic transformation are also presented.

Synthesis, Structure, and magnetism of a rhombic metallocycle

A rhombic metallocycle [CoII6Cl6(L)2(HL)2]·5.5DMF·3.5H2O (1) (H2L = tris(2-naphthimidazolylmethyl) amine) composed of two CoIICl(HL) moieties and two CoIICl(L) moieties alternately bridged by two μ3-CoII ions has been synthesized under solvothermal condition. Each metallocycle associate with its six neighbors through intermolecular π···π interactions between naphthimidazolylmethyl arms forming a supramolecular framework with a pcu network. Magnetic measurements on the metallocycle reveal dominant antiferromagnetic couplings between CoII centers.

Gold nanocrystal-loaded 2D supramolecular network for plasmon-enhanced nitrogen fixation

Plasmon-enhanced catalysis showing high NH3 production rate and recyclability over polyoxometalate-based two-dimensional supramolecular frameworks loading gold nanocrystals is conducted under visible and near-infrared light irradiation.

Crystal Structure, Hirhfeld surface Analysis and IR Analysis of 2-amino-1,9-dihydro-6H-purin-6-one-selenate-water

A new guanine complex was synthesized and the structure was elucidated by SXRD and IR spectroscopic methods. Single-crystal X-ray diffraction analysis (SXRD) was used to describe the crystal structure. Triclinic, in the space group P-1, with the following properties: a=9.5945(3), b=13.1171(3), c=14.1905(3), α =79.756(2), β =82.036(2), γ =84.902(2)°, V=1736.70(8) Å3, Z=2. N−H···O, O−H···O and C−H···O hydrogen bonds connect the molecules in the crystal, creating a three-dimensional supramolecular framework. The title structure is stabilized by the intra and intermolecular strong hydrogen bonds, according to a Hirshfeld surface analysis of the recorded intermolecular interactions. For the title complex, the two main interactions are H···O/ O··H (36.5%) and H···H (23.7 %).

Enantiomeric filtration separation of supramolecular framework membranes.

A two-dimensional supramolecular framework with a tetragonal structure is constructed via host-guest interaction of a pillar[5]arene grafted polyanion with a modified porphyrin. The membrane of the framework with a chiral counterion exhibits enantiomeric selectivity during the filtration of racemic molecules with amino groups, demonstrating broadened potential in chiral separations.

Self-assembly synthesis of Ru nanoparticles anchored on B, N co-doping carbon support for hydrogen evolution: Electronic state induced by the strong metal-support interactions

The strong metal-support interactions between metal and its support have been considered as an effective way to improve the electrocatalytic activity in heterogeneous catalysis, which can modulate metal d-band's energy level and, consequently, affect the adsorption/desorption of the intermediates on the metal nanoparticle's surface. In this paper, we use a self-assembly strategy for construction nano-sized Ru nanoparticles (NPs) anchored on B, N co-doping carbon nanorod carrier (Ru/BCN) as HER catalyst by using unique boron cluster-organic framework as precursor and self-sacrificing templates. This supramolecular framework forming with cucurbit [6]uril as the host and closo-[B12H12]2- as the guest can feature unique hexagonal nanorod morphology to confine the Ru NPs into framework through weak reductivity of closo-[B12H12]2-. After pyrolysis, the strong metal-support interactions between B, N co-doping carbon support (BCN) and Ru NPs have been found due to the synergistic coupling effect of co-dopants B and N, which can increase electron transfer between the metal nanoparticle and support. The overpotentials of 33 mV and 40 mV are required for as-prepared catalyst Ru/BCN to achieve a current density of 10 mA cm−2 in alkaline and acidic conditions, respectively, which are approximately one third of those of Ru/CN. These findings demonstrate that our synthetic way offers a potential route for fabricating co-doping carbon with B and N atoms to support Ru NPs with enhanced HER performance in pH-independent conditions.

Supramolecular Framework Constructed by Dendritic Nanopolymer for Stable Flexible Perovskite Resistive Random-Access Memory.

The 3D supramolecular framework (3D-SF) is constructed in this work through the hydrogen bond assisted self-assembly of spherical dendritic nanopolymer to regulate the flexibility, stability, and resistive switching (RS) performance of perovskite resistive random-access memory (RRAM). Herein, the 3D-SF network acts as the perovskite crystallization template to regulate the perovskite crystallization process due to its coordination interaction of functional groups with the perovskite grains, presenting the uniform, pinhole-free, and compact perovskite morphology for stable flexible RRAM. The 3D-SF network in situ stays at the perovskite intergranular boundaries to crosslink the perovskite grains. The RS performance of 3D-SF-modified perovskite RRAM device is evidently improved to the ON/OFF ratio of 105 , the cycle number of 500 times, and the data retention time of 104 s. The 50-days exposure of unencapsulated RRAM device at ambient environment still makes the ON/OFF ratio to be kept at ≈104 , indicating the potential of long-term stable multilevel storage in the high-density data storage. The bending action under different radius also does not change the RS performance due to the excellent bending-resistant ability of 3D-SF-modified perovskite film. This work explores a novel polymer additive strategy to construct the 3D supramolecular framework for stable flexible perovskite optoelectronic devices.

A cellulose-derived supramolecule for fast ion transport.

Supramolecular frameworks have been widely synthesized for ion transport applications. However, conventional approaches of constructing ion transport pathways in supramolecular frameworks typically require complex processes and display poor scalability, high cost, and limited sustainability. Here, we report the scalable and cost-effective synthesis of an ion-conducting (e.g., Na+) cellulose-derived supramolecule (Na-CS) that features a three-dimensional, hierarchical, and crystalline structure composed of massively aligned, one-dimensional, and ångström-scale open channels. Using wood-based Na-CS as a model material, we achieve high ionic conductivities (e.g., 0.23 S/cm in 20 wt% NaOH at 25 °C) even with a highly dense microstructure, in stark contrast to conventional membranes that typically rely on large pores (e.g., submicrometers to a few micrometers) to obtain comparable ionic conductivities. This synthesis approach can be universally applied to a variety of cellulose materials beyond wood, including cotton textiles, fibers, paper, and ink, which suggests excellent potential for a number of applications such as ion-conductive membranes, ionic cables, and ionotronic devices.

Supramolecular self-assembly between symmetric tetramethyl cucurbit[6]uril and dimethylphenylpiperazine hydrochloride

The interaction between symmetric tetramethyl cucurbit[6]uril (TMeQ[6]) and 2,3-dimethylphenylpiperazine hydrochloride (PMY) has been studied in the presence of [CdCl4]2−. Each port of the TMeQ[6] is connected to PMY through weak interactions such as ion dipole interactions and CH⋯O hydrogen bonding interactions, whilst the [CdCl4]2− is connected with the portal carbonyl oxygen, glycoside urea methylene and a bridging methylene of a TMeQ[6] molecule via ion–dipole interactions. These interactions were evident from a single crystal X-ray diffraction study of TMeQ[6]-PMY-[CdCl4]2−. In addition, the complex can form a one-dimensional supramolecular chain structure, and then assemble into a two-dimensional supramolecular framework, which can be described as a TMeQ[6]-PMY-[CdCl4]2− based supramolecular framework (QSF).

A “heat set” Zr-Diimide based Fibrous Metallogel: Multiresponsive Sensor, Column-based Dye Separation, and Iodine Sequestration

Sensing and monitoring hazardous contaminants in water and radioactive iodine sequestration is pivotal due to their detrimental impact on biological ecosystems. In this context, herein, a water stable zirconium-diimide based metallogel (Zr@MG) with fibrous columnar morphology is accomplished through the “heat set” method. The presence of diimide linkage with long aromatic chain manifests active luminescence properties in the linker as well as in the supramolecular framework structure. The as-synthesized Zr@MG xerogel can selectively detectCr2O72- (LOD = 0.52 ppm) and 2,4,6-trinitrophenol (TNP) (LOD = 80.2 ppb) in the aqueous medium. The Zr@MG paper strip-based detection for Cr2O72- and nitro explosive makes this metallogel reliable and an attractive luminescent sensor for practical use. Moreover, a column-based dye separation experiment was performed to show selective capture of positively charged methylene blue (MB) dye with 98 % separation efficiency from the mixture of two dyes. Also, the Zr@MG xerogel showed effective iodine sequestration from the vapor phase (232 wt%).

Q[8]-based frameworks exhibiting clustering-triggered emission and responses to organic molecules

The outer surface interaction of cucurbit[n]urils (Q[n]s) is an important supramolecular interaction that results from the positive electrostatic potential on the outer surface of Q[n]s. It cannot only result in the formation of various novel Q[n]-based supramolecular frameworks, but can also lead to clustering emission of Q[n]s. In this work, three different Q[8]-based supramolecular frameworks, assembled through the outer surface interaction of Q[n]s (OSIQ), were prepared according to the literature. The solid-state clustering-triggered emission (CTE) characteristics of the frameworks were also determined. Moreover, investigation of their adsorption properties showed that the solid-state CTE of the three Q[8]-based supramolecular frameworks was quenched in the presence of certain chemicals and that they exhibited high selectivity for pyridine. Framework B exhibited the highest adsorption of pyridine.

Two Cu(II) microporous frameworks based on a bifunctional linker and selective gas adsorption properties for CO2

Two microporous metal-organic frameworks assembled of Cu(II) ions and bifunctional imidazoly/carboxylate containing organic compound (4-(1H-imidazole-4-yl) benzoate), namely [Cu2(L)4]·DMA·3H2O (1) and [Cu(L)2]·2H2O (2), are structurally characterized. Compound 1 shows 3-fold interpenetrating binodal 4-connected CdSO4 microporous architecture with Point (Schläfli) symbol of (65·8), while complex 2 is a supramolecular framework by stacking in an ···AAA··· configuration from two-dimensional 44 layers with one-dimensional open channels with 11.99 ​× ​11.99 ​Å2. MOF 1 shows selective adsorption capacity for CO2 (32.24 ​cm3/g) over N2 and CH4, while 2 has the uptake of 45.67 ​cm3/g for CO2 and 23.81 ​cm3/g for CH4. The corresponding the heat of adsorption calculated by Clausius–Clapeyron equation are 28.5 and 32.3 ​kJ ​mol−1. The adsorption capacity of CO2 is comparative higher than CH4 and N2, ascribing to the electrostatic interactions between CO2 and narrow pores decorated with uncoordinated imidazoly-N atoms.

High Water-Assisted Proton Conductivities of Two Cadmium(II) Complexes Constructed from Zwitterionic Ligands.

Finding more metal complexes with outstanding water stability and high proton conductivity still has important research significance for the energy field. Herein, two highly proton-conductive complexes, one hydrogen-bonded supramolecular framework (HSF) [Cd(CBIA)2(H2O)4]·2H2O (1) and one coordination polymer (CP), {[Cd2(CBIA)2(4,4'-bipy)2(H2O)2]·(CBIA)·(OH)·2H2O}n (2) (4,4'-bipy = 4,4'-bipyridine), were triumphantly assembled using a zwitterionic organic compound, 2-(1-(carboxymethyl)-1H-benzo[d]imidazol-3-ium-3-yl)acetate (HCBIA). In the structure of HSF 1, there are several coordination and lattice H2O units except for the two monodentate CBIA- anions. CP 2 with a one-dimensional (1D) cylindrical structure has free CBIA- units and free H2O units located in the cavity. Thanks to the ability of the uncoordinated carboxyl groups and coordination/lattice water molecules to construct the rich H-bonding networks, both complexes exhibit super-high proton conductivities, reaching 5.09 × 10-3 and 3.41 × 10-3 S cm-1 under 100 °C/98% relative humidity (RH), respectively. Based on the exploration of crystal structure data, combined with the calculated activation energy, and adsorption/desorption plots of nitrogen and water vapor, the causes and differences in proton conductivity of the two complexes, especially the proton-conductive mechanism, are compared and analyzed. This study again confirms that the zwitterionic ligands can exert important effects on forming organo-inorganic hybrid materials with high proton conductivity.

Polymorphism from a 1:1 Ln:BTB reaction pot: Solvothermal versus sonochemical synthesis of Ln-MOFs

A 1:1 reaction pot of lanthanide(III):1,3,5-benzenetrisbenzoate (Ln(III):BTB) in a 2:1 mixture of DMF/H2O was subject to solvothermal and sonochemical conditions in order to form new Ln-BTB polymorphs. Solvothermal crystal growth is time dependent, yielding a new MOF structure Nd4(BTB)4(H2O)10•(H2O)7 (1) after 1–2 days and two new analogues of Ln(BTB)(H2O), Nd(BTB)(H2O) (2) and Sm(BTB)(H2O) (3) after 3.5 days. Sonochemical synthesis produced a pure phase of Ln(BTB)(H2O)2•(H2O)2(DMF)3 (4–7, Ln = Nd3+ (4), Eu3+ (5), Tb3+ (6), and Er3+ (7)). Compound 1 is a novel 3-D framework that consists of undulating one-dimensional lanthanide-carboxylate secondary building unit (SBU) chains connected by BTB linkers, which pack into a hxl topology with rhombohedral and hexagonal channels. The total solvent accessible void space is 4581.6 Å3 which constitutes 37 % of the of the total unit cell volume. Compounds 2 and 3 are three-dimensional microporous networks consisting of mutually parallel-perpendicular, infinite, undulating one-dimensional metal-carboxylate SBU chains interlinked by BTB ligands. Compounds 4–7 were previously reported from four different synthetic protocols and feature Ln2(COO)6(H2O)4 SBUs linked by BTB linkers into a two-dimensional (3,6-connected) kgd network, which assembles via hydrogen bonds into a three-dimensional supramolecular framework. Gas adsorption studies on compound 4 indicate microporous and mesoporous sites that contribute relatively high Langmuir and BET surface areas up to 1161 m2/g and 671 m2/g, respectively. Eu(BTB)(H2O)2•(H2O)2(DMF)3 (5) displays strong luminescence under UV excitation and is a highly sensitive and selective sensor for Fe3+ ions and nitroaromatic compounds. Sensing occurs via luminescence quenching due to competitive absorption of excitation energy between the BTB framework and the analyte molecules.

Selective and Reversible Solvent Uptake in Tetra-4-(4-pyridyl)phenylmethane-based Supramolecular Organic Frameworks.

The dynamic behavior of supramolecular organic frameworks (SOFs) based on the rigid tetra-4-(4-pyridyl)phenylmethane (TPPM) organic tecton has been elucidated through 3D electron diffraction, X-ray powder diffraction and differential scanning calorimetry (DSC) analysis. The SOF undergoes a reversible single-crystal-to-single-crystal transformation when exposed to vapours of selected organic solvents, moving from a closed structure with isolated small voids to an expanded structure with solvated channels along the b axis. The observed selectivity is dictated by the fitting of the guest in the expanded SOF, following the degree of packing coefficient. The effect of solvent uptake on TPPM solid-state fluorescence was investigated, evidencing a significant variation in the emission profile only in the presence of chloroform.

Synthesis and spectral studies of Ni(Ⅱ) complexes involving functionalized dithiocarbamates and triphenylphosphine: X-ray crystal structure, thermal stability, Hirshfeld surface analysis, DFT and biological evaluation

New homoleptic [Ni(cpebdtc)2] (1), [Ni(cptpdtc)2] (2) and heteroleptic [Ni(cpebdtc)(NCS)(PPh3] (3), and [Ni(cptpdtc)(NCS)(PPh3] (4) complexes were synthesized and fully characterized by CHNS analysis, FT-IR, electronic, 1H, 13C NMR spectroscopy. In heteroleptic complexes (3, 4), the values of thiocyanide (ѵC-N) have been moved towards longer wavenumbers and the carbon signals of NCS2 have been moved to downfield in comparison to the homoleptic complexes (1, 2), thus suggests increased strength of thioureide bond because of π-accepting phosphine. Structure of complex 3 was obtained by single crystal X-ray diffraction technique that showed NiS2PN square planar distorted geometry around nickel atom. In complex 3, supramolecular frameworks are stabilized by π…π non-covalent interactions. The HOMO/LUMO energy values displayed satisfying interchange of a charge that takes place within a molecule. Molecular electrostatic potential (MEP) surface analysis has been performed to reveal charge distribution in the complex. Natural bond orbital (NBO) assessment has been done to demonstrate the donor–acceptor interconnections. The calculation of Fukui function was performed by population evaluation. The quantification of intermolecular interactions was obtained by Hirshfeld surface analysis. TG analyses of complexes (1 and 2) showed single step decomposition with the formation of binary NiS material. All the complexes showed significant scavenging activity. The in vitro antifungal potential of complexes (1–4) against three Candida strains (C. albicans, C. glabrata and C. tropicalis) by taking Fluconazole (FLC) as a reference drug, showed that 3 exhibit significant activity with MIC around 500 µg/ml against all strains. The hypochromism effect suggested that complexes 2 and 4 interacted with the Ct-DNA through an intercalative binding mode, which was further validated by molecular docking studies.

A new heteroleptic cuprous polymer constructed by a cyanopyridine ligand exhibiting a supramolecular framework structure and luminescence.

Luminescent cuprous complexes are of great importance among coordination compounds due to their relative abundance, low cost and ability to display excellent luminescence. The title heteroleptic cuprous polymer solvate, catena-poly[[[(9,9-dimethyl-9H-xanthene-4,5-diyl)bis(diphenylphosphane)-κ2P,P'](μ-pyridine-3-carbonitrile-κ2N1:N3)copper(I)] hexafluorophosphate dichloromethane trisolvate], {[Cu(C6H4N2)(C39H32OP2)]PF6·3CH2Cl2}n, conventionally abbreviated as {[Cu(3-PyCN)(Xantphos)]PF6·3CH2Cl2}n, where Xantphos and 3-PyCN represent (9,9-dimethyl-9H-xanthene-4,5-diyl)bis(diphenylphosphane) and pyridine-3-carbonitrile, respectively, has been described. In this polymer solvate, the asymmetric unit consists of three dichloromethane solvent molecules, a hexafluorophosphate anion and a polymeric heteroleptic cuprous complex cation, in which the cuprous centre is in a CuP2N2 tetrahedral coordination and is coordinated by two P atoms from the Xantphos ligand and two N atoms from two 3-PyCN ligands (the pyridyl and cyano N atoms). It is through the connection of the μ2-bridging 3-PyCN ligand that these cuprous centres are linked into a one-dimensional helical chain structure. The chains are further assembled through C-H...π interactions to form a supramolecular metal-organic framework containing solvent-accessible channels. The UV-Vis absorption and photoluminescence properties of this heteroleptic cuprous polymer have been studied on as-synthesized samples. Its luminescence emission should mainly originate from the metal-to-ligand charge transfer excited state.

Supramolecular Organic Frameworks as Adsorbents for Efficient Removal of Excess Bilirubin in Hemoperfusion.

Excess bilirubin accumulates in the bodies of patients suffering from acute liver failure (ALF) to cause much irreversible damage and bring about serious clinical symptoms such as kernicterus, hepatic coma, or even death. Hemoperfusion is a widely used method for removing bilirubin from the blood, but clinically used adsorbents have unsatisfactory adsorption capacity and kinetics. In this study, we prepared four supramolecular organic framework microcrystals SOF-1-4 via slow evaporation of their aqueous solutions under infrared light. SOF-1-4 possess good regularity and excellent stability. We demonstrate that all the four SOFs could serve as adsorbents for bilirubin with fast adsorption kinetics within 20 min and ultrahigh adsorption capacity of 609.1 mg g-1, driven by electrostatic interaction and hydrophobicity. The superior adsorption performance of the SOFs outperformed most of the reported bilirubin adsorbents. Remarkably, SOF-3 could remove about 90% of bilirubin in the presence of 40 g L-1 BSA with a minimal loss of albumin and was thus further processed to a bead-shaped composite with a diameter of 2 mm with poly(ether sulfone) (PES). This PES-loaded SOF could efficiently adsorb bilirubin to the normal level from human plasma with an adsorption equilibrium concentration of 7.8 mg L-1 in 6 h through a dynamic hemoperfusion process. This work provides a new vitality for the development of novel bilirubin adsorbents for hemoperfusion therapy.

PPh3H]2[SbCl5]: A Zero-Dimensional Hybrid Metal Halide with a Supramolecular Framework and Stable Dual-Band Emission

Zero-dimensional (0D) organic–inorganic metal halides (OIMHs) have attracted tremendous attention due to their fascinating optoelectronic properties. Herein, we report an antimony(III)-based 0D OIMH of [PPh3H]2[SbCl5] comprising discrete [SbCl5]2– pyramids and protonated triphenylphosphine (PPh3H) cations with a low charge density. Abundant supramolecular interactions including C–H···Cl and rare P–H···Cl hydrogen bonds and C–H···Π and anion···Π interactions lead to a three-dimensional (3D) supramolecular framework structure of [PPh3H]2[SbCl5]. Photophysical characterizations indicate that [PPh3H]2[SbCl5] has singlet/triplet dual-band emission. The intersystem crossing between the single and triplet states is tunable upon changing the temperature. Analyses of the Huang–Rhys factor (S), exciton activation energy (Ea), and electron–phonon coupling energy (Γop) verify that the soft lattice and strong electron–phonon coupling result in the broad emission of [PPh3H]2[SbCl5], while the excited-state reorganization of the [SbCl5]2– pyramid leads to a large Stokes shift. DFT calculations help provide a deep understanding on the optical property of [PPh3H]2[SbCl5]. The title compound could remain stable for more than 1 year without the obvious decay of emission, which may be related to the rigid 3D supramolecular framework.