Cage-Based Metal-Organic Framework Featuring a Double-Yolk Core-Shell UL@UL Structure for Iodine Capture.

Cage-based MOFs, with their customizable chemical environments and precisely controllable nanospaces, show great potential for the selective adsorption of guest molecules with specific structures. In this work, we have constructed a novel cage-based MOF [(CH)NH][(UO)(TMTTA)]·11.5DMF·2HO (IHEP-51), utilizing a triazine derivative poly(carboxylic acid), 4,4',4″-(((1,3,5-triazine-2,4,6-triyl)tris(((4-carboxycyclohexyl)methyl)azanediyl))tris(methylene))tribenzoic acid (HTMTTA), as an organic ligand and uranyl as a metal node.

4f/5d Hybridization Induced Single-Electron Delocalization in an Azide-Bridged Dicerium Complex.

Dilanthanide complexes with one-electron delocalization are important targets for understanding the specific 4f/5d-bonding feature in lanthanide chemistry. Here, we report an isolable azide-bridged dicerium complex [{(Trapen)Ce}(μ-N)] [Trapen = tris (2-aminobenzyl)amine; TMS = SiMe], which is synthesized by the reaction of tripodal ligand-supported (Trapen)CeCl complex with NaN. The structure and bonding nature of are fully characterized by X-ray crystal diffraction analysis, electron paramagnetic resonance (EPR), magnetic measurement, cyclic voltammetry, X-ray absorption spectroscopy, and quantum-theoretical studies.

Th-Based Multicomponent Heterometallic Metal-Organic Frameworks Featuring 6,12-Connected Topology for Iodine Adsorption.

Its high coordination number and tendency to cluster make Th suitable for constructing metal-organic frameworks (MOFs) with novel topologies. In this work, two novel thorium-based heterometallic MOF isomers (IHEP-17 and IHEP-18) were assembled from a Th cluster, a multifunctional organic ligand [4-(1-pyrazol-4-yl)benzoic acid (HPyba)], and Cu/Ni cations via the one-pot solvothermal synthesis strategy. The framework features a 6,12-connected new topology net and contains two kinds of supramolecular cage structures, ThM and ThM, suitable for guest exchange.

Colossal negative thermal expansion in a cucurbit[8]uril-enabled uranyl-organic polythreading framework thermally induced relaxation.

It is an ongoing goal to achieve the effective regulation of the thermal expansion properties of materials. In this work, we propose a method for incorporating host-guest complexation into a framework structure and construct a flexible cucurbit[8]uril uranyl-organic polythreading framework, U(bcbpy)(CB8). U(bcbpy)(CB8) can undergo huge negative thermal expansion (NTE) and has a large volumetric coefficient of -962.

Unveiling Structural Diversity of Uranyl Compounds of Aprotic 4,4'-Bipyridine ,'-Dioxide Bearing O-Donors.

As an aprotic O-donor ligand, 4,4'-bipyridine ,'-dioxide (DPO) shows good potential for the preparation of uranyl coordination compounds. In this work, by regulating reactant compositions and synthesis conditions, diverse coordination assembly between uranyl and DPO under different reaction conditions was achieved in the presence of other coexisting O-donors. A total of ten uranyl-DPO compounds, U-DPO-1 to U-DPO-10, have been synthesized by evaporation or hydro/solvothermal treatment, and the possible competition and cooperation of DPO with other O-donors for the formation of these uranyl-DPO compounds are discussed.

Synthesis of Trapen Ligand-Based U(IV) and Th(IV) 2-Phosphaethynolate Complexes and Comparison of Covalency with Corresponding Ti(IV) Analogues.

The involvement of the 2-phosphaethynolate anion species with ambident nucleophilic properties serves as an essential protocol for synthesizing oxygen-bound or phosphorus-bound complexes. This work mainly describes the synthesis and characterization of U, Th, and Ti phosphaethynolate complexes featuring a preferential O-coordination fashion. Among these complexes, the first examples of a Ti(IV)-OCP complex 3A, Th(IV)-OCP complex 3B, and U(IV)-OCP complex 3C were assembled by a salt metathesis reaction between M(Trapen)(Cl) (M = Ti, Th, U) and NaOCP(dioxane) and were all crystallographically characterized.

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

Controlling the orderly assembly of molecular building blocks for the formation of the desired architectural, chemical, and physical properties of the resulting solid-state materials remains a long-term goal and deserves to be examined. In this work, we propose a patterning strategy for modular assembly and structural regulation of mixed-ligand uranyl coordination polymers (CPs) through the combination of couples of organic ligands with complementary molecular geometry and well-matched coordination modes. By using a 5-(-tolyldiazenyl)isophthalic acid ligand (Hptdi) with different rigid linear bicarboxylic acid linkers to construct a well-defined ladder-like pattern, five novel isostructural uranyl coordination polymers, [(UO)(ptdi)(bdc)](dma) (), [(UO)(ptdi)(bpdc)](dma) (), [(UO)(ptdi)(tpdc)](dma) (), [(UO)(ptdi)(ndc)](dma) (), and [(UO)(ptdi) (pdc)](dma) () {Hbdc, 1,4-dicarboxybenzene; Hbpdc, 4,4'-biphenyldicarboxylic acid; Htpdc, terphenyl-4,4″-dicarboxylic acid; Hndc, 2,6-naphthalenedicarboxylic acid; Hpdc, 1,6-pyrenedicarboxylic acid; [dma], [(CH)NH]}, were successfully synthesized.

Controllable photomechanical bending of metal-organic rotaxane crystals facilitated by regioselective confined-space photodimerization.

Molecular machines based on mechanically-interlocked molecules (MIMs) such as (pseudo) rotaxanes or catenates are known for their molecular-level dynamics, but promoting macro-mechanical response of these molecular machines or related materials is still challenging. Herein, by employing macrocyclic cucurbit[8]uril (CB[8])-based pseudorotaxane with a pair of styrene-derived photoactive guest molecules as linking structs of uranyl node, we describe a metal-organic rotaxane compound, U-CB[8]-MPyVB, that is capable of delivering controllable macroscopic mechanical responses. Under light irradiation, the ladder-shape structural unit of metal-organic rotaxane chain in U-CB[8]-MPyVB undergoes a regioselective solid-state [2 + 2] photodimerization, and facilitates a photo-triggered single-crystal-to-single-crystal (SCSC) transformation, which even induces macroscopic photomechanical bending of individual rod-like bulk crystals.

Coordination-Adaptive Polydentate Pseudorotaxane Ligand for Capturing Multiple Uranyl Species.

The propensity of uranyl for hydrolysis in aqueous environments prevents precise control of uranyl species in the scenarios of on-demand separation and tailored synthesis. Herein, using cucurbit[7]uril (CB[7]) as the macrocyclic molecule and 4,4'-bipyridine-N,N'-dioxide (DPO) as the string molecule, we propose a new kind of multidentate pseudorotaxane ligand, DPO@CB[7] for capturing uranyl species at different pH's. With the aprotic nature of DPO for metal coordination, the coordination ability of the DPO@CB[7] ligand is less affected by pH and can work in a wide range of pH's.

Mixed-Ligand Uranyl Squarate Coordination Polymers: Structure Regulation and Redox Activity.

The electron-rich squarate ion (CO, ) possesses electronic delocalization over the entire molecule and good redox activity, and the functionalization of metal-organic complexes with the group is desirable. In this work, a mixed-ligand method is used to construct novel uranyl squarate coordination polymers utilizing 4,4'-bipyridine (), 4,4'-bipyridine-,'-dioxide (), 1,10-phenanthroline (), 4,4'-vinylenedipyridine (), and in situ formed oxalate () as ancillary ligands. Seven mixed-ligand uranyl compounds, [(UO)(OH)()](H) (), [(UO)(HO)()](H) (), (UO)(HO)()()·2HO (), (UO)(HO)()()·HO (), (UO)(OH)()()·HO (), [(UO)()()](H) (), and [(UO)()()](H) (), with varying crystal structures were synthesized under hydrothermal conditions.

Selective Separation of Am(III)/Eu(III) by the QL-DAPhen Ligand under High Acidity: Extraction, Spectroscopy, and Theoretical Calculations.

Although 1,10-phenanthroline-based ligands have recently shown vast opportunities for the separation of trivalent actinides (Ans(III)) from lanthanides (Lns(III)), the optimization and design of the extractant structure based on the phenanthroline framework remain hotspots for further improving the separation. Following the strategy of hard and soft donor atom combination, for the first time, the quinoline group was attached to the 1,10-phenanthroline skeleton, giving a lipophilic ligand, 2,9-diacyl-bis((3,4-dihydroquinoline-1((2H)-yl)-1),10-phenanthroline (QL-DAPhen)), for Am(III)/Eu(III) separation. In the presence of sodium nitrate, the ligand can effectively extract Am(III) over Eu(III) in HNO solution, with the separation factor () ranging from 29 to 44.

Proximity Effect in Uranyl Coordination of the Cucurbit[6]uril-Bipyridinium Pseudorotaxane Ligand for Promoting Host-Guest Synergistic Chelating.

In the present work, we proposed regulating uranyl coordination behavior of cucurbituril-bipyridinium pseudorotaxane ligand by utilizing meta-functionalized bipyridinium dicarboxylate guest. A tailored pseudorotaxane precursor involving 1,1'-(hexane-1,6-diyl)bis(3-cyanopyridin-1-ium) bromide () and cucurbit[6]uril (CB[6]) has designed and synthesized. Through in situ hydrolysis of the pseudorotaxane ligands and their coordination assembly with uranyl cations, seven new uranyl-rotaxane coordination polymers have been obtained under hydrothermal conditions in the presence of different anions.

An Azobenzene-Modified Photoresponsive Thorium-Organic Framework: Monitoring and Quantitative Analysis of Reversible Photoisomerization.

Monitoring and quantification of the photoresponsive behavior of metal-organic frameworks that respond to a light stimulus are crucial to establish a clear structure-activity relationship related to light regulation. Herein, we report the first azobenzene-modified photoresponsive thorium-organic framework ( with the formula [ThO(OH)(HO)] (H = ()-2'--tolyldiazenyl-1,1':4',4'-terphenyl-4,4″-dicarboxylic acid), in which the utilization of a thorium cluster as a metal node leads to one of the largest pore sizes among all the azobenzene-containing metal-organic frameworks (MOFs). The phototriggered transformation of the isomer to the isomer is monitored and characterized quantitatively by comprehensive analyses of NMR and UV spectroscopy, which reveals that the maximum isomerization ratio of in the solid state is 19.

Solar-Driven Nitrogen Fixation Catalyzed by Stable Radical-Containing MOFs: Improved Efficiency Induced by a Structural Transformation.

Herein we present a new viologen-based radical-containing metal-organic framework (RMOF) Gd-IHEP-7, which upon heating in air undergoes a single-crystal-to-single-crystal transformation to generate Gd-IHEP-8. Both RMOFs exhibit excellent air and water stability as a result of favorable radical-radical interactions, and their long-lifetime radicals result in wide spectral absorption in the range 200-2500 nm. Gd-IHEP-7 and Gd-IHEP-8 show excellent activity toward solar-driven nitrogen fixation, with ammonia production rates of 128 and 220 μmol h  g , respectively.

Molecular Spring-like Triple-Helix Coordination Polymers as Dual-Stress and Thermally Responsive Crystalline Metal-Organic Materials.

Elastic metal-organic materials (MOMs) capable of multiple stimuli-responsiveness based on dual-stress and thermally responsive triple-helix coordination polymers are presented. The strong metal-coordination linkage and the flexibility of organic linkers in these MOMs, rather than the 4 Å stacking interactions observed in organic crystals, causes the helical chain to act like a molecular spring and thus accounts for their macroscopic elasticity. The thermosalient effect of elastic MOMs is reported for the first time.

A mixed-ligand strategy regulates thorium-based MOFs.

Two novel thorium-based organic frameworks (Th-IHEP-5 and Th-IHEP-6) were assembled from a hexanuclear thorium cluster, porphyrin derivative ligand and linear carboxylic acid ligands via a mixed-ligand strategy. As a stable heterogeneous catalyst, Th-IHEP-5 exhibited high photocatalytic activity for the oxidation of 2-chloroethyl ethyl sulfide (CEES) and the fixation of CO2. The good catalytic effect is attributed to the large conjugated system of porphyrin and the photosensitizer enhancing effects of bipyridine.

Metal-Carboxyl Helical Chain Secondary Units Supported Ion-Exchangeable Anionic Uranyl-Organic Framework.

As a less explored avenue, actinide-based metal-organic frameworks (MOFs) are worth studying for the particularity of actinide nodes in coordination behaviour and assembly modes. In this work, an azobenzenetetracarboxylate-based anionic MOF supported by uranyl-carboxyl helical chain units was synthesized, incorporating linear uranyl as the metal centre. This kind of helical chain-type building unit is reported for the first time in uranyl-based MOFs.

Releasing Metal-Coordination Capacity of Cucurbit[6]uril Macrocycle in Pseudorotaxane Ligands for the Construction of Interwoven Uranyl-Rotaxane Coordination Polymers.

As an emerging type of actinide hybrid material, uranyl-rotaxane coordination polymers (URCPs) with new coordination patterns and topological structures are still desired. In this work, we propose a new strategy to construct URCPs by promoting the simultaneous coordination of both the wheel and axle moieties in pseudorotaxane linkers with metal nodes. Starting from a series of cucurbit[6]uril (CB[6])-based pseudorotaxane ligands, C nBPCA@CB[6] [C nBPCA = 1,1-(α,ω-diyl)bis[4-(ethoxycarbonyl)pyridin-1-ium] bromides, where n = 5-8] with slightly deformed CB[6], four new URCPs (URCP1, URCP3, URCP4, and URCP5) with interwoven network structures, as well as another noninterwoven polymer(URCP2), have been successfully prepared.

Actinide-Based Porphyrinic MOF as a Dehydrogenation Catalyst.

Uranyl-organic frameworks (UOFs) have recently been the object of many research endeavors due to the unique coordination mode of uranyl ions and their attractive physicochemical properties. Here, a new (3,4)-connected UOF (U-IHEP-4) assembled from uranyl and porphyrin ligand tetrakis(4-carboxyphenyl)porphyrin (H4TCPP) is reported, which represents the first case of actinide porphyrinic MOFs. Adsorption experiments in DMF solution demonstrated that U-IHEP-4 selectively adsorbs positively charged dyes, which is in line with its negatively charged framework and large pore volume ratio (90 %).

Large-Pore 3D Cubic Mesoporous (KIT-6) Hybrid Bearing a Hard-Soft Donor Combined Ligand for Enhancing U(VI) Capture: An Experimental and Theoretical Investigation.

A preorganized tetradentate phenanthrolineamide (DAPhen) ligand with hard and soft donors combined in the same molecule has been found to possess high extraction ability toward actinides over lanthanides from acidic aqueous solution in our previous work. Herein we grafted phenanthrolineamide groups onto a large-pore three-dimensional cubic silica support by the reaction of DAPhen siloxane with KIT-6 substrate to prepare a novel uranium-selective sorbent, KIT-6-DAPhen. The as-synthesized sorbent was well-characterized by scanning electron microscopy, high-resolution transmission electron microscopy, N adsorption/desorption, X-ray diffraction, FT-IR, C cross-polarization magic-angle spinning NMR, and TGA techniques, which confirmed the consummation of the functionalization.