Multi-stimuli-responsive luminescence enabled by crown ether anchored chiral antimony halide phosphors.

Stimuli-responsive optical materials have provided a powerful impetus for the development of intelligent optoelectronic devices. The family of organic-inorganic hybrid metal halides, distinguished by their structural diversity, presents a prospective platform for the advancement of stimuli-responsive optical materials. Here, we have employed a crown ether to anchor the A-site cation of a chiral antimony halide, enabling convenient control and modulation of its photophysical properties. The chirality-dependent asymmetric lattice distortion of inorganic skeletons assisted by a crown ether promotes the formation of self-trapped excitons (STEs), leading to a high photoluminescence quantum yield of over 85%, concomitant with the effective circularly polarized luminescence. The antimony halide enantiomers showcase highly sensitive stimuli-responsive luminescent behaviours towards excitation wavelength and temperature simultaneously, exhibiting a versatile reversible colour switching capability from blue to white and further to orange. In situ temperature-dependent luminescence spectra, time-resolved luminescence spectra and theoretical calculations reveal that the multi-stimuli-responsive luminescent behaviours stem from distinct STEs within zero-dimensional lattices. By virtue of the inherent flexibility and adaptability, these chiral antimony chlorides have promising prospects for future applications in cutting-edge fields such as multifunctional illumination technologies and intelligent sensing devices.

Trace removal of benzene vapour using double-walled metal-dipyrazolate frameworks.

In principle, porous physisorbents are attractive candidates for the removal of volatile organic compounds such as benzene by virtue of their low energy for the capture and release of this pollutant. Unfortunately, many physisorbents exhibit weak sorbate-sorbent interactions, resulting in poor selectivity and low uptake when volatile organic compounds are present at trace concentrations. Herein, we report that a family of double-walled metal-dipyrazolate frameworks, BUT-53 to BUT-58, exhibit benzene uptakes at 298 K of 2.47-3.28 mmol g-1 at <10 Pa. Breakthrough experiments revealed that BUT-55, a supramolecular isomer of the metal-organic framework Co(BDP) (H2BDP = 1,4-di(1H-pyrazol-4-yl)benzene), captures trace levels of benzene, producing an air stream with benzene content below acceptable limits. Furthermore, BUT-55 can be regenerated with mild heating. Insight into the performance of BUT-55 comes from the crystal structure of the benzene-loaded phase (C6H6@BUT-55) and density functional theory calculations, which reveal that C-H···X interactions drive the tight binding of benzene. Our results demonstrate that BUT-55 is a recyclable physisorbent that exhibits high affinity and adsorption capacity towards benzene, making it a candidate for environmental remediation of benzene-contaminated gas mixtures.

Enhanced Gas Uptake in a Microporous Metal-Organic Framework via a Sorbate Induced-Fit Mechanism.

Physical adsorption of gas molecules in microporous materials is an exothermic process, with desorption entropy driving a decrease in uptake with temperature. Enhanced gas sorption with increasing temperature is rare in porous materials and is indicative of sorbate initiated structural change. Here, sorption of C2H6, C3H6, and C3H8 in a flexible microporous metal-organic framework (MOF) {Cu(FPBDC)]·DMF}n (NKU-FlexMOF-1) (H2FPBDC = 5-(5-fluoropyridin-3-yl)-1,3-benzenedicarboxylic acid) that increases with rising temperature over a practically useful temperature and pressure range is reported along with other small molecule and hydrocarbon sorption isotherms. Single X-ray diffraction studies, temperature-dependent gas sorption isotherms, in situ and variable temperature powder X-ray diffraction experiments, and electronic structure calculations were performed to characterize the conformation-dependent sorption behavior in NKU-FlexMOF-1. In total, the data supports that the atypical sorption behavior is a result of loading-dependent structural changes in the flexible framework of NKU-FlexMOF-1 induced by sorbate-specific guest-framework interactions. The sorbates cause subtle adaptations of the framework distinct to each sorbate providing an induced-fit separation mechanism to resolve chemically similar hydrocarbons through highly specific sorbate-sorbent interactions. The relevant intermolecular contacts are shown to be predominantly repulsion and dispersion interactions. NKU-FlexMOF-1 is also found to be stable in aqueous solutions including toleration of pH changes. These experiments demonstrate the potential of this flexible microporous MOF for cost and energy efficient industrial hydrocarbon separation and purification processes. The efficacy for the separation of C3H6/C3H8 mixtures is explicitly demonstrated using NKU-FlexMOF-1a (i.e., activated NKU-FlexMOF-1) for a particular useful temperature range.

Soft Porous Crystal Based upon Organic Cages That Exhibit Guest-Induced Breathing and Selective Gas Separation.

Soft porous crystals (SPCs) that exhibit stimuli-responsive dynamic sorption behavior are attracting interest for gas storage/separation applications. However, the design and synthesis of SPCs is challenging. Herein, we report a new type of SPC based on a [2 + 3] imide-based organic cage (NKPOC-1) and find that it exhibits guest-induced breathing behavior. Various gases were found to induce activated NKPOC-1 crystals to reversibly switch from a "closed" nonporous phase (α) to two porous "open" phases (ß and γ). The net effect is gate-opening behavior induced by CO2 and C3 hydrocarbons. Interestingly, NKPOC-1-α selectively adsorbs propyne over propylene and propane under ambient conditions. Thus, NKPOC-1-α has the potential to separate binary and ternary C3 hydrocarbon mixtures, and the performance was subsequently verified by fixed bed column breakthrough experiments. In addition, molecular dynamics calculations and in situ X-ray diffraction experiments indicate that the gate-opening effect is accompanied by reversible structural transformations. The adsorption energies from molecular dynamics simulations aid are consistent with the experimentally observed selective adsorption phenomena. The understanding gained from this study of NKPOC-1 supports the further development of SPCs for applications in gas separation/storage because SPCs do not inherently suffer from the recyclability problems often encountered with rigid materials.

Selective gas adsorption and fluorescence sensing response of a Zn(ii) metal-organic framework constructed by a mixed-ligand strategy.

By means of a mixed-ligand strategy, a novel bi-functional metal-organic framework, [H2N(CH3)2]·Zn(NDC)(atz)·H2O (NDC = 2,6-naphthalenedicarboxylic acid, Hatz = 1H-tetrazol-5-amine), was synthesized, which displays a three-dimensional two-fold interpenetrated framework. Owing to the introduction of two different functional organic ligands, this complex exhibits bi-functional properties, i.e., selective gas adsorption of CO2 over CH4 and fluorescence sensing response for nitrobenzene.

Two microporous Fe-based MOFs with multiple active sites for selective gas adsorption.

Two Fe-based porous MOFs have been constructed from dimeric Fe-clusters and rod-shaped heterobimetallic {Fe2Na3}n chains as SBUs, respectively. Both of them exhibit highly selective CO2 adsorption over CH4 and N2, owing to their abundant multiple active sites.

Structural stabilization of a metal-organic framework for gas sorption investigation.

By inserting a ligand into a reported metal-organic framework (), the reformed aggregation of triangle grids () shows enhanced stability. In addition, owing to its structural characteristic, the also reveals a certain CO2 storage ability and CO2/CH4 adsorption selectivity as expected.

Divalent metal ions modulated strong frustrated M(II)-Fe(III)3O (M = Fe, Mn, Mg) chains with metamagnetism only in a mixed valence iron complex.

Linking magnetically frustrated triangular FeO units by divalent metal ions (M(II) = Fe(II) for 1, Mn(II) for 2) gives isostructural 1D spin chains. Strong antiferromagnetic interactions were found in these complexes with significant frustrations but very interesting ferrimagnetic like transition and metamagnetism were found in mixed valence 1. By comparing the magnetic behaviours with isostructural complex 3 (with M(II) = Mg(II)), it is proposed that the spins of Fe(II) ions and Mn(II) ions have ferromagnetic and antiferromagnetic contributions respectively.

Two microporous MOFs constructed from different metal cluster SBUs for selective gas adsorption.

Two microporous MOFs have been constructed from different metal cluster SBUs. Both of them exhibit highly selective CO2 adsorption capacity over CH4 and N2 owing to their abundant active sites.

A series of cobalt and nickel clusters based on thiol-containing ligands accompanied by in situ ligand formation.

Eight cobalt and nickel clusters with the formulae [Co4(µ4-O)(MBT)5(µ2-Piv)] (1), [Ni3(MBT)2(L1)2(OCH3)2] (2), [Ni4(µ3-S)(µ3-S2)(MBT)2(L2)] (3), [Ni4(L3)4] (4), [Ni6(µ4-S)3(MBT)6]·(C2H5OH)2 (5), H[Co4(µ4-O)(HMBI)6]·(NO3)(TEA)0.5(CH3OH)2(H2O) (6), [Ni2(HMBI)4]·(CH3OH)2 (7), and [Ni5(MBI)2(HMBI)4(OCH3)2]·(CH3OH)3(H2O)2 (8) (HPiv = pivalic acid, HL1 = 2-disulfanylbenzo[d]thiazole, H2L2 = (Z)-2-((2-mercaptophenyl)imino)benzo[d]thiazole-3(2H)-thiol, H2L3 = (Z)-2-(benzo[d]thiazol-2(3H)-ylideneamino)benzenethiol, TEA = triethylamine) have been solvothermally prepared via assembling distinct metal resource and thiol-containing ligands 2-mercaptobenzothiazole (HMBT)/2-mercaptobenzimidazole (H2MBI). Complexes 1 and 6 are tetrahedral cobalt clusters. Complex 2 features linear arrangement of nickel ions. Complexes 3 and 4 are tetranuclear nickel clusters with the butterfly and square shape, respectively. Complex 5 displays a trigonal prism geometry. Complexes 7 and 8 exhibit paddle-wheel and trigonal bipyramidal geometry, respectively. The starting ligand HMBT undergoes in situ ligand transformation in the formation of the nickel clusters, and the new generated inorganic ligands (S(2-) and S2(2-)) and organic ligands (HL1, H2L2 and H2L3) were captured within the metallic cores. Magnetic studies indicate that complexes 1 and 6 show dominating antiferromagnetic couplings and that spin frustration exists in 6.

A polypyridyl-pyrene based off-on Cd²âº fluorescent sensor for aqueous phase analysis and living cell imaging.

By retaining the quadrapyridyl receptor of polypyridylhexaazatriphenylene (a Cd(2+) sensor reported by us) and extending its chromophoric group with pyrene, a chemical sensor (1) was designed and synthesized in this work. This sensor exhibit selective off-on fluorescence response to Cd(2+) over other metal ions, and the detection limit is as low as 0.02 µM. The Cd(2+) sensing of 1 has high water toleration and can be carried out in the media with the water content up to 70%. Additionally, 1 was successfully applied to the in vivo imaging of intracellular Cd(2+) in living HaLa cells, and showed low cytotoxicity and cell membrane permeability in these experiments. These results suggest that 1 has potential application in the Cd(2+) analysis of environmental and biological samples.

Two hexaazatriphenylene based selective off-on fluorescent chemsensors for cadmium(II).

Two hexaazatriphenylene (HAT) derivatives, 2,3,6,7-tetramethyl-10,11-di(pyridin-2-yl)dipyrazino[2,3-f:2',3'-h]quinoxaline (1) and 2,3-dimethyl-6,7,10,11-tetra(pyridin-2-yl)dipyrazino[2,3-f:2',3'-h]quinoxaline (2), were designed and synthesized. Both 1 and 2 exhibited high off-on fluorescent selectivity for Cd(2+) over many other metal ions, and the detection limits were determined to be 0.6 and 5.0 µM, respectively. The stoichiometry and coordination mode of blue fluorescent 1-Cd(2+) and cyan fluorescent 2-Cd(2+) were determined with fluorescence titration fit, Job's plot analysis, (1)H NMR titration and X-ray crystallography, and the fluorescence enhancement mechanism was analyzed with density functional theory calculation.

Microporous organic polymers for gas storage and separation applications.

Microporous organic polymers (MOPs), an emerging class of functional porous materials featured with the pure organic component have been widely studied in recent years. These materials have potential uses in areas such as storage, separation, and catalysis. In this Perspective, we focused on the gas storage and separation of MOPs. The targeted design and synthesis of MOPs toward the enhancement of gas capacity and selectivity are discussed. Furthermore, special emphasis is given to the post-synthesis modification of MOPs which have been proved to be effective methods to accurately tune the desired properties.

The role of order-disorder transitions in the quest for molecular multiferroics: structural and magnetic neutron studies of a mixed valence iron(II)-iron(III) formate framework.

Neutron diffraction studies have been carried out to shed light on the unprecedented order-disorder phase transition (ca. 155 K) observed in the mixed-valence iron(II)-iron(III) formate framework compound [NH(2)(CH(3))(2)](n)[Fe(III)Fe(II)(HCOO)(6)](n). The crystal structure at 220 K was first determined from Laue diffraction data, then a second refinement at 175 K and the crystal structure determination in the low temperature phase at 45 K were done with data from the monochromatic high resolution single crystal diffractometer D19. The 45 K nuclear structure reveals that the phase transition is associated with the order-disorder of the dimethylammonium counterion that is weakly anchored in the cavities of the [Fe(III)Fe(II)(HCOO)(6)](n) framework. In the low-temperature phase, a change in space group from P31c to R3c occurs, involving a tripling of the c-axis due to the ordering of the dimethylammonium counterion. The occurrence of this nuclear phase transition is associated with an electric transition, from paraelectric to antiferroelectric. A combination of powder and single crystal neutron diffraction measurements below the magnetic order transition (ca. 37 K) has been used to determine unequivocally the magnetic structure of this Néel N-Type ferrimagnet, proving that the ferrimagnetic behavior is due to a noncompensation of the different Fe(II) and Fe(III) magnetic moments.

Valence-induced assembly of Cu(I)-Cu(II) ions into different discrete coordination architectures by a disk-shaped polypyridyl ligand.

The valences of metal ions were found to play key roles in controlling the formation and structures of discrete coordination architectures in a copper and disk-shaped hexa-monodentate ligand system. When Cu(I) and Cu(II) ions react with a polydentate ligand HPDQ, a hexanuclear "double-decker" like discrete "LM(3)M(3)L" coordination architecture (CuI)(6)(HPDQ)(2)(CHCl(3))(8) (complex 1), and a "LM(3)L + LM(3)" composite structure complex (Cu(NO(3))(2))(6)(HPDQ)(3) (complex 2) are formed, respectively.

A sixfold interpenetrated microporous MOF constructed from heterometallic tetranuclear cluster exhibiting selective gas adsorption.

A sixfold interpenetrated microporous MOF has been constructed from a heterometallic tetranuclear cluster. The framework contains two types of 1D micro-channels along different directions. Moreover, this compound exhibits high selective gas sorption for H(2) over N(2).

A highly selective on/off fluorescence sensor for cadmium(II).

A polypyridyl ligand, 2,3,6,7,10,11-hexakis(2-pyridyl)dipyrazino[2,3-f:2',3'-h]quinoxaline (HPDQ), was found to have excellent fluorescent selectivity for Cd(2+) over many other metal ions (K(+), Na(+), Ca(2+), Mg(2+), Mn(2+), Fe(2+), Ni(2+), Co(2+), Cu(2+), Ag(+), Hg(2+), Zn(2+), and Cr(3+)) based on the intramolecular charge-transfer mechanism, which makes HPDQ a potential fluorescence sensor or probe for Cd(2+). An obvious color change between HPDQ and HPDQ + Cd(2+) can be visually observed by the naked eye. The structure of the complex HPDQ-Cd has been characterized by X-ray crystallography. Density functional theory calculation results on the HPDQ and HPDQ-Cd complexes could explain the experimental results.

New three-dimensional porous metal organic framework with tetrazole functionalized aromatic carboxylic Acid: synthesis, structure, and gas adsorption properties.

5-(1H-Tetrazol-1-yl)isophthalic acid (H(2)L) reacts with Cu(II) ion forming a new metal-organic framework {[CuL]·DMF·H(2)O}(∞) (1) (DMF = N,N-dimethylformamide), with a rutile-related type net topology. Compound 1 possesses a 3D structure with 1D channels that can be desolvated to yield a microporous material. Adsorption properties (N(2), H(2), O(2), CO(2), and CH(4)) of the desolvated solid [CuL] (1a) have been studied, and the results exhibit that 1a possesses fairly good capability of gas sorption for N(2), H(2), O(2), and CO(2) gases, with high selectivity ratios for O(2) over H(2) at 77 K and CO(2) over CH(4) at 195, 273, and 298 K. Furthermore, 1a has excellent O(2) uptake at 77 K and a remarkably high quantity of adsorption for CO(2) at room temperature (298 K) and atmospheric pressure, suggesting its potential applications in gas separation or purification.

Two unprecedented 10-connected bct topological metal-organic frameworks constructed from cadmium clusters.

By simply modifying the expansion of ligand tether length, two Cd(ii) metal-organic frameworks have been constructed from linear tetranuclear and trinuclear cadmium clusters, respectively, which present an unprecedented 10-connected uninodal bct net.

One-dimensional metal-azido complex constructed by a double EO azido bridged trinuclear nickel(II) unit: synthesis, structure and magnetic properties.

The hydrothermal reaction of Ni(NO(3))(2).6H(2)O, NaN(3) phenanthroline and nicotinic acid yielded a one-dimensional (1D) complex, [Ni(1.5)(N(3))(2)(phen)(nic)](n) (1) (phen = phenanthroline, nic = nicotinate), which is a new example of the named orbital countercomplementarity-like complex. In 1, the nicotinate shows mu(3)-nic-N,O,O coordination mode, and the azide groups adopt mu(1,1) bridging mode linking Ni(II) ions to form a rare trinuclear Ni(II) unit bridged by a double mu(1,1) azido.