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Abstract: Thus far, reports about the transformations for dynamic crystals of supramolecular coordination systems mainly include single‐crystal‐to‐single‐crystal reactions, and solvent‐mediated processes. This Concept focuses on the mechanisms for solvent‐mediated structural transformations of dynamic crystals, which can be classified into two categories, that is, core‐on‐shell and core‐to‐core. The core‐on‐shell mechanism means that the core of the new crystal is generated from the shell of original crystal, being concomitant with the dissolution of the mother crystal. In contrast, for the core‐to‐core case, the growth of new crystal core and the dissolution of original crystal core will proceed simultaneously, but they are physically separated. Herein, the two mechanisms are elucidated in detail, with some typical examples from recent advances. [ABSTRACT FROM AUTHOR]

Currently, no unequivocal evidence is given for elucidation of 'black box' during the structural transformations of dynamic crystalline materials. Here, three types of mechanisms are revealed for such transformations through X-ray diffraction and optical microscopy; namely, single-crystal to single-crystal (SC-SC), as well as 'core-to-core' and 'core-on-shell' processes. As confirmed by time-lapse optical microscopy, the latter two cases can be properly ascribed as partial recrystallization processes, while the former one is a continuous process with two different crystal lattices simultaneously maintained in one single crystal. Interestingly, these three distinct pathways can be exquisitely realized by changing only the halogen substituent (from -F, -Cl, to -Br) of the organic ligands in the coordination supramolecular systems. [ABSTRACT FROM AUTHOR]

A series of nine coordination polymers {[Cd(L)2(solvent) x](solvent) y} n have been prepared from Cd(NO3)2 and 5-bromonicotinic acid (HL) in different solvents through a layered diffusion method. By using CH3OH/H2O at different volume ratios of 1:1 and 1:3, a one-dimensional (1D) coordination species ( 1 a) and a three-dimensional (3D) (3,6)-connected framework ( 2 a⋅g1) can be obtained. A similar self-assembly process in C2H5OH/H2O or H2O/1,4-dioxane gives 2 a⋅g2 or 2 a⋅g3, which are isomorphic to 2 a⋅g1 but with different lattice solvents. Replacement of the mixed solvents with DMF/H2O (v/v 1:1 or 1:3) also gives a 1D chain complex ( 1 b) or a 3D microporous framework ( 2 b⋅g1). Similarly, MOF 2 b⋅g2 can be assembled from CH3CN/H2O as an isomorphic solvate of 2 b⋅g1. Significantly, the 3D MOF families of 2 a⋅g n and 2 b⋅g n are supramolecular isomers even though they are topologically equivalent. Also, if a mixture of CH3OH/CH2Cl2 (v/v 1:1 or 3:1) is used, a pair of distinct MOFs ( 3 a⋅g) and ( 3 b) are generated as pseudo-polymorphs that show a two-dimensional (2D) sheet and a 3D coordination framework, respectively. Furthermore, mutual solvent-induced conversions were realized between 1 a and 1 b and between 2 a⋅g1, 2 a⋅g2, and 2 a⋅g3 following the size-dependent rule of the solvent. These results are of great significance in recognizing the solvent effect upon coordination assemblies and their crystal transformations. [ABSTRACT FROM AUTHOR]

Nuclear industry spent fuel reprocessing and some radioactive contamination sites often involve high acidity and salinity environments. Currently developed and reported sorbents in 99TcO4− sequestration from the nuclear waste are unstable and show low adsorption efficiency in harsh conditions. To address this issue, we developed a post‐synthetic modification strategy by grafting imidazole‐based ionic liquids (ILs) onto the backbone of covalent organic framework (COF) via vinyl polymerization. The resultant COF‐polyILs sorbent exhibits fast adsorption kinetics (<5 min) and good sorption capacity (388 mg g−1) for ReO4− (a nonradioactive surrogate of 99TcO4−). Outstandingly, COF‐polyILs composite shows superior ReO4− removal even under highly acidic conditions and in the presence of excess competing ions of Hanford low‐level radioactive waste stream, benefiting from the stable covalent bonds between the COF and polyILs, mass of imidazole rings, and hydrophobic pores in COF. [ABSTRACT FROM AUTHOR]

Four benzeneboron‐capped mononuclear CoII complexes with different alkyl substitutions on the fourth position of phenylboronic acid were obtained. The CoII ions are all wrapped by the pocket‐like ligands and located in trigonal prismatic coordination geometries. Alternating‐current magnetic susceptibility measurements reveal that they show different magnetization dynamics, such as distinct relaxation rates at the same temperature, the faster QTM rates for the ethyl and propyl substituted complexes, as well as different relaxation processes. Magneto‐structural correlation study reveals that the various deviations of coordination geometry of CoII ion, diverse crystal packings and possible different vibration modes of substituents caused by modifying alkyl chains are the key factors affecting the magnetization dynamics. This work demonstrates that the alkyl chains even locating far away from the metal center can have a large impact on the magnetic behavior of the CoII complex with a very rigid coordination geometry, offering a new perspective towards transition metal based single‐molecule magnets. [ABSTRACT FROM AUTHOR]

Enantioselective sensing is highly crucial and challenging due to the highly similar physical/chemical properties of enantiomers which may have different chemical impact on organism. Luminescent coordination compounds have attracted great attention as sensing materials based on their controllable chemical and electric structures that can be highly matched with the targeted species. To achieve high‐performance enantioselective sensing, the direct synthesis of chiral and luminescent bifunctional coordination compounds is a rational way but highly challenging due to the price and synthesis difficulty. Herein, an anionic coordination‐chain‐based hydrogen‐bonded framework was applied as a host to accommodate chiral and luminescent centers via a facile cation exchange reaction, affording a bifunctional framework that possesses enantioselective sensing properties for the mixture of enantiomers. This study paves a pathway for constructing multifunctional coordination chain‐based hydrogen‐bonded frameworks for rapidly enantioselective sensing function. [ABSTRACT FROM AUTHOR]

Three types of mechanisms regulated by halogen substituent effect, namely single‐crystal to single‐crystal transformation as well as “core‐to‐core” and “core‐on‐shell” processes, have been confirmed for elucidation of the “black box” during structural transformations of dynamic crystalline materials. The combination of time‐lapse optical microscopy and X‐ray single‐crystal diffraction techniques provides a convenient and straightforward approach to reveal the transformation mechanisms. More information can be found in the Communication by M. Du et al. on page 12985. [ABSTRACT FROM AUTHOR]

Invited for the cover of this issue is the group of Miao Du at Tianjin Normal University. The image depicts the structural transformation of a dynamic coordination network. Read the full text of the article at . [ABSTRACT FROM AUTHOR]

A cage‐based metal–organic framework (Ni‐NKU‐101) with biphenyl‐3,3',5,5'‐tetracarboxylic acid was synthesized via solvothermal method. Ni‐NKU‐101 contains two types of cages based on trinuclear and octa‐nuclear nickel‐clusters that are connected with each other by the 4‐connected ligands, to form a 3D framework with a new topology. A mixed‐metal strategy was used to synthesize isostructural bimetallic MOFs of MxNi1‐x‐NKU‐101 (M=Mn, Co, Cu, Zn). The electrocatalytic studies showed that the hydrogen evolution reaction (HER) activity of CuxNi1‐x‐NKU‐101 is much higher than that of other MxNi1‐x‐NKU‐101 catalysts in acidic aqueous solution, owing to the synergistic effect of the bimetallic centers. The optimized Cu0.19Ni0.81‐NKU‐101 has an overpotential of 324 mV at 10 mA cm−2 and a Tafel slope of 131 mV dec−1. The mechanism of HER activity over these bimetallic MOF‐based electrocatalysts are discussed in detail. [ABSTRACT FROM AUTHOR]

Entacapone (ENT) is a powerful catechol‐O‐methyl transferase inhibitor that is used for the diagnosis and treatment of Parkinson's syndrome, but the amount used must be well controlled to avoid overtreatment and side effect. Fast and selective detection of ENT needs well‐matched energy levels and well‐designed sensor‐ENT interaction which is highly challenging. In this work, a water stable europium‐based metal‐organic framework (Eu‐TDA) was synthesized to detect ENT by luminescence with excellent reusability and selectivity in the presence of main coexisting and interference species of plasma with a limit of detection of 5.01 μM. The experimental results showed that the luminescence of Eu‐TDA can be effectively quenched by ENT via well‐designed photoinduced electron transfer mechanism and internal filtration effect mechanism in the system. [ABSTRACT FROM AUTHOR]

An inorganic-organic hybrid surfactant with a hexavanadate cluster as the polar head group was designed and observed to assemble into micelle structures, which further spontaneously coagulate into a 1D anisotropic structure in aqueous solutions. Such a hierarchical self-assembly process is driven by the cooperation of varied noncovalent interactions, including hydrophobic, electrostatic, and hydrogen-bonding interactions. The hydrophobic interaction drives the quick formation of the micelle structure; electrostatic interactions involving counterions leads to the further coagulation of the micelles into larger assemblies. This process is similar to the crystallization process, but the specific counterions and the directional hydrogen bonding lead to the 1D growth of the final assemblies. Since most of the hexavanadates are exposed to the surface, the 1D assembly with nanoscale thickness is a highly efficient heterogeneous catalyst for the oxidation of organic sulfides with appreciable recyclability. [ABSTRACT FROM AUTHOR]

Photocatalytic hydrogen evolution by water splitting is highly important for the application of hydrogen energy and the replacement of fossil fuel by solar energy, which needs the development of efficient catalysts with long‐term catalytic stability under light irradiation in aqueous solution. Herein, Zn0.5Cd0.5S solid solution was synthesized by a metal–organic framework‐templated strategy and then loaded with MoS2 by a hydrothermal method to fabricate a MoS2/Zn0.5Cd0.5S heterojunction for photocatalytic hydrogen evolution. The composition of MoS2/Zn0.5Cd0.5S was fine‐tuned to obtain the optimized 5 wt % MoS2/Zn0.5Cd0.5S heterojunction, which showed a superior hydrogen evolution rate of 23.80 mmol h−1 g−1 and steady photocatalytic stability over 25 h. The photocatalytic performance is due to the appropriate composition and the formation of an intimate interface between MoS2 and Zn0.5Cd0.5S, which endows the photocatalyst with high light‐harvesting ability and effective separation of photogenerated carriers. [ABSTRACT FROM AUTHOR]

CO2 is considered as the primary greenhouse gas, resulting in a series of serious environmental problems that affect people's life and health. Carbon capture and sequestration has been implemented as one of the most appealing pathways to control and use CO2. Here, we rationally integrate various functional sites within the confined nanospace of a microporous metal–organic framework (MOF) material, which is constructed by mixed‐ligand strategy based on metal‐adeninate vertices. It not only exhibits excellent stability but also can efficiently transform CO2 and epoxides to cyclic carbonates under mild and cocatalyst‐free conditions. Additionally, this catalyst shows extraordinary recyclability for the CO2 cycloaddition reaction. [ABSTRACT FROM AUTHOR]

Photomechanical molecular crystals are receiving much attention due to their efficient conversion of light into mechanical work and advantages including faster response time; higher Young's modulus; and ordered structure, as measured by single‐crystal X‐ray diffraction. Recently, various photomechanical crystals with different motions (contraction, expansion, bending, fragmentation, hopping, curling, and twisting) are appearing at the forefront of smart materials research. The photomechanical motions of these single crystals during irradiation are triggered by solid‐state photochemical reactions and accompanied by phase transformation. This Minireview summarizes recent developments in growing research into photoresponsive molecular crystals. The basic mechanisms of different kinds of photomechanical materials are described in detail; recent advances in photomechanical crystals for promising applications as smart materials are also highlighted. [ABSTRACT FROM AUTHOR]

As one of the most efficient systems for photocatalytic hydrogen evolution, the Z‐Scheme system, consisting of different semiconductors with a reversible donor–acceptor pair, has attracted great attention. Considering the non‐toxicity and low cost of photocatalysts, a series of g‐C3N4/α‐Fe2O3 hybrids were rationally constructed based on the Z‐Scheme mechanism for the first time, using a metal‐organic framework template approach that can fine tune the compositions and properties of the hybrids. An optimized hybrid, g‐C3N4/α‐Fe2O3‐2, exhibited prominent photocatalytic water splitting performance with a visible light response. Under irradiation of visible light (λ>420 nm), the hybrid shows a high durability and superior hydrogen production rate of 2066.2 μmol g−1 h−1 from water splitting, which is approximately three times greater than that of bulk g‐C3N4 because of the effective separation of photo‐excited charge carriers by two narrow band gap semiconductors, tightly coupled with the Z‐Scheme structural feature. Green hybrid: A Z‐Scheme system, g‐C3N4/α‐Fe2O3, was synthesized by a MOF‐derived template method. The optimized system shows excellent photocatalytic hydrogen evolution performance with visible light response. [ABSTRACT FROM AUTHOR]

Abstract: Increasing both the energy barrier for magnetization reversal and the coercive field of the hysteresis loop are significant challenges in the field of single‐molecule magnets (SMMs). Coordination geometries of lanthanide ions and magnetic interactions between lanthanide ions are both important for guiding the magnetic behavior of SMMs. We report a high energy barrier of 657 K (457 cm−1) in a diamagnetic‐ion‐diluted lanthanide chain compound with a constrained bisphenoid symmetry (D2d); this energy barrier is substantially higher than the barrier of 567 K (394 cm−1) of the non‐diluted chain compound with intrachain ferromagnetic interactions. Although intrachain magnetic interaction lowers the energy barrier for magnetization reversal, it can greatly enhance the coercive fields and zero‐field remanence of the hysteresis loops, which is crucial for the rational design of high‐performance SMMs. Factors related to the coordination sphere of the lanthanide center, which govern the high magnetic relaxation barriers through the second excited Kramer's doublets and the magnetic interactions that affect the hysteresis loops, were revealed through ab initio calculations. [ABSTRACT FROM AUTHOR]

Abstract: Two unique ZnI‐containing MOFs {[ZnI8ZnII3(H2O)x(HL)12](OH)2⋅13 H2O}n (x=6, 1; x=2, 2) (HL=tetrazole monoanion) with high‐nuclearity Zn‐cages were prepared successfully. These Zn‐cages are constructed from [ZnI8] clusters with multi‐centered ZnI−ZnI bonds and ZnII ions. [ZnI8] clusters in 1 and 2 display Oh and D4h symmetry, respectively. Importantly, eight [ZnI8] clusters and six ZnII ions form a large [Zn70] nanocage in 1. To our knowledge, this is the first MOF based on polynuclear Zn‐cages consisting of ZnI and ZnII ions. Compared with reported ZnI‐species, 1 and 2 display high thermal and solvent stabilities. Theoretical investigations based on DFT calculations uncover that effective 4s‐4s orbital overlap and electron delocalization through these a1g+t1u molecular orbitals on [ZnI8] clusters lead to considerable aromatic stabilization, which can explain well the intrinsic stability of 1 and 2. Interestingly, 1 can behave as a luminescent probe to detect the toxic CrVI ions in aqueous. [ABSTRACT FROM AUTHOR]

Abstract: The applications of three‐dimensional superstructures that consist of metal–organic framework (MOF) crystals are promising, but limited by spatial control over the crystallization process. Here a hydrophobic hierarchical metal–organic framework (HZIF‐8) containing unusual micro‐, meso‐, and macropores was designed and synthesized by a template strategy, in which the polystyrene (PS) not only acted as the template to construct the macropores, but also modified the hydrophilic crystal surface of ZIF‐8. When used as adsorbent for liquid oil/water separation, HZIF‐8 demonstrated significantly enhanced oil adsorption performance while maintaining very low water uptake. [ABSTRACT FROM AUTHOR]

Luminescent 3D lanthanide metal-organic framework (Ln-MOF) {[Tb2(TATAB)2] ⋅4 H2O ⋅6 DMF} n ( 1) was synthesized under solvothermal conditions by using flexible ligand 4,4′,4′′- s-triazine-1,3,5-triyltri- p-aminobenzoate (TATAB). A phase transition was observed between low temperature and room temperature. The luminescence of 1 could be enhanced by formaldehyde and quenched efficiently by trace amounts of benzaldehyde in solvents such as benzyl alcohol (0.01-2.0 vol %) and ethanol (0.01-2.5 vol %). This is the first use of a Ln-MOF as chemical sensor for both formaldehyde and benzaldehyde. The high sensitivity and selectivity of the luminescence response of 1 to benzaldehyde allows it to be used as an excellent sensor for identifying benzaldehyde and provides a simple and convenient method for detecting traces of benzaldehyde in benzyl alcohol based injections. This work establishes a new strategy for detection of benzaldehyde in benzyl alcohol by luminescent MOFs. [ABSTRACT FROM AUTHOR]

A promising alternative strategy for designing mesoporous metal-organic frameworks (MOFs) has been proposed, by modifying the symmetry rather than expanding the length of organic linkers. By means of this approach, a unique MOF material based on the target [Zn8(ad)4] (ad=adeninate) clusters and C3-symmetric organic linkers can be obtained, with trigonal microporous (ca., 0.8 nm) and hexagonal mesoporous (ca., 3.0 nm) 1D channels. Moreover, the resulting 446-MOF shows distinct reactivity to transition and lanthanide metal ions. Significantly, the transmetalation of CoII or NiII on the ZnII centers in 446-MOF can enhance the sorption capacities of CO2 and CH4 (16-21 %), whereas the impregnation of EuIII and TbIII in the channels of 446-MOF will result in adjustable light-emitting behaviors. [ABSTRACT FROM AUTHOR]

A series of six-coordinate lanthanide complexes {(H3O)[Ln(NA)2]⋅H2O} n (H2NA=5-hydroxynicotinic acid; Ln=GdIII ( 1⋅Gd); TbIII ( 2⋅Tb); DyIII ( 3⋅Dy); HoIII ( 4⋅Ho)) have been synthesized from aqueous solution and fully characterized. Slow relaxation of the magnetization was observed in 3⋅Dy. To suppress the quantum tunneling of the magnetization, 3⋅Dy diluted by diamagnetic YIII ions was also synthesized and magnetically studied. Interesting butterfly-like hysteresis loops and an enhanced energy barrier for the slow relaxation of magnetization were observed in diluted 3⋅Dy. The energy barrier (Δ τ) and pre-exponential factor ( τ0) of the diluted 3⋅Dy are 75 K and 4.21×10−5 s, respectively. This work illustrates a successful way to obtain low-coordination-number lanthanide complexes by a framework approach to show single-ion-magnet-like behavior. [ABSTRACT FROM AUTHOR]

An inorganic–organic hybrid surfactant with a hexavanadate cluster as the polar head group underwent stepwise assembly into micelles and finally, a 1D nanobelt structure with the cooperation of hydrophobic, electrostatic, and hydrogen‐bonding interactions; these last interactions are directional and lead to the anisotropic assemblies. The nanobelts are highly efficient heterogeneous catalysts for the oxidation of organic sulfides because most of the hexavanadates are exposed to the surface, showing its potential application in the petroleum industry and in environmentally benign chemistry. For more details see the Full Paper by T. Li, Y. Wei, T. Liu et al. on page 9589 ff. [ABSTRACT FROM AUTHOR]

A rare, robust microporous lanthanide metal-organic framework with 1D honeycomb-type channels is presented. Excellent adsorption capabilities for N2, H2, and CO2 and significant selective sorption of CO2 over N2 and CH4 were observed. Moreover, the guest-dependent luminescent behavior of these lanthanide materials shows a potential use for the sensing of small-molecule pollutants such as benzene and acetone. [ABSTRACT FROM AUTHOR]

The combination of the anisotropic DyIII ion and organic radicals as spin carriers results in discrete and one-dimensional lanthanide-radical magnetic materials, namely, [Dy(hfac)3(NITThienPh)2] ( 1) and [Dy2(hfac)6(NITThienPh)2] n ( 2; hfac=hexafluoroacetylacetonate, NITThienPh=2-(5-phenyl-2-thienyl)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide). Linking monomeric 1 with the DyIII ion leads to the formation of polymeric 2, and the transformation between them is chemically controllable and reversible. The characterization of both static and dynamic magnetic properties shows that the dominant intrachain exchange interaction is important to observe magnetic bistability in 2 rather than that in 1. Monomeric 1 exhibits paramagnetic behavior, whereas polymeric 2 shows the unusual coexistence of superparamagnetic and two-step field-induced metamagnetic behaviors. The antiferromagnetic ground state of 2 does not prevent the dynamic relaxation of the magnetization with the finite-sized effect in the lanthanide-radical system. Energy barriers to thermally activated relaxation for 2 are 53 and 98 K in the low- and high-temperature regimes, respectively. A hysteresis loop is observed with the coercive field of 99 Oe at 2 K. [ABSTRACT FROM AUTHOR]

Two 3D heterometal-organic frameworks based on infrequent trigonal bipyramidal Ln5 clusters as nodes were structurally and magnetically characterized (Ln=Gd ( 1), Dy ( 2)). The results indicate large MCE of up to 30.7 J kg−1 K−1 in 1 and slow magnetic relaxation behavior in 2. Expectedly, constructing 3D MOFs based on multinuclear clusters as nodes may will be a new strategy for achieving large −Δ Sm. Additionally, compound 1 exhibits high thermal and solvent stabilities, providing a favorable foundation for realistic applications. [ABSTRACT FROM AUTHOR]

Cover Feature: Rational Construction of an Exceptionally Stable MOF Catalyst with Metal-Adeninate Vertices toward CO2 Cycloaddition under Mild and Cocatalyst-Free Conditions (Chem. Eur. J. 49/2019) B An exceptionally stable b metal-organic framework (MOF) can be rationally constructed by mixed-ligand strategy, based on Zn SP II sp -adeninate vertices and 2,2'-dimethyl-4,4'-azodibenzoate linkers. As a result, it can serve as a high-efficiency heterogeneous catalyst for cycloaddition of CO SB 2 sb with epoxides to afford cyclic carbonates under mild conditions without solvent or cocatalyst. [Extracted from the article]

The rational preparation of mesoporous metal – organic frameworks (MOFs) represents a great challenge for their intrinsic resistance of crystalline lattice extension to form large cavities. In their Full Paper on page 9713 ff., M. Du, C. ‐ S. Liu et al. report a mesoporous ZnII coordination framework designed by a new strategy of ligand symmetry modulation, which shows unique dual reactivity to transition and lanthanide metals via cation exchange or guest inclusion. Moreover, the modified MOFs materials possess enhanced gas uptake capacities and adjustable light emissions. [ABSTRACT FROM AUTHOR]