A Spiderweb‐Like Metal–Organic Framework Multifunctional Foam

Processing metal–organic frameworks (MOFs) into hierarchical macroscopic materials can greatly extend their practical applications. However, current strategies suffer from severe aggregation of MOFs and limited tuning of the hierarchical porous network. Now, a strategy is presented that can simultaneously tune the MOF loading, composition, spatial distribution, and confinement within various bio‐originated macroscopic supports, as well as control the accessibility, robustness, and formability of the support itself. This method enables the good dispersion of individual MOF nanoparticles on a spiderweb‐like network within each macrovoid even at high loadings (up to 86 wt %), ensuring the foam pores are highly accessible for excellent adsorption and catalytic capacity. Additionally, this approach allows the direct pre‐incorporation of other functional components into the framework. This strategy provides precise control over the properties of both the hierarchical support and MOF.     

A Microporous Anionic Metal–Organic Framework for Sensing Luminescence of Lanthanide(III) Ions and Selective Absorption of Dyes by Ionic Exchange

Herein, a novel anionic framework with primitive centered cubic (pcu) topology, [(CH₃)₂NH₂]₄[(Zn₄dttz₆)Zn₃]?15 DMF?4.5 H₂O, ( IFMC‐2 ; H₃dttz=4,5‐di(1H‐tetrazol‐5‐yl)‐2H‐1,2,3‐triazole) was solvothermally isolated. A new example of a tetranuclear zinc cluster {Zn₄dttz₆} served as a secondary building unit in IFMC‐2 . Furthermore, the metal cluster was connected by Zn^II ions to give rise to a 3D open microporous structure. The lanthanide(III)‐loaded metal–organic framework (MOF) materials Ln³⁺@IFMC‐2 , were successfully prepared by using ion‐exchange experiments owing to the anionic framework of IFMC‐2 . Moreover, the emission spectra of the as‐prepared Ln³⁺@IFMC‐2 were investigated, and the results suggested that IFMC‐2 could be utilized as a potential luminescent probe toward different Ln³⁺ ions. Additionally, the absorption ability of IFMC‐2 toward ionic dyes was also performed. Cationic dyes can be absorbed, but not neutral and anionic dyes, thus indicating that IFMC‐2 exhibits selective absorption toward cationic dyes. Furthermore, the cationic dyes can be gradually released in the presence of NaCl.     

The Uncommon Channel‐Based Ln‐MOFs for Highly Selective Fe3+ Detection and Superior Rhodamine B Adsorption

Two new isostructural 3D lanthanide–organic frameworks [H₂N(Me)₂] [Ln₃(OH)(bpt)₃(H₂O)₃] (DMF)₂?(H₂O)₄ ( 1‐Ln ; Ln=Sm and Eu) with a 1D channel (25 Å) have been successfully assembled from the rare trinuclear [Ln₃(OH)(COO)₉] clusters and biphenyl‐3,4′,5‐tricarboxylic acid (H₃bpt) and exhibit high stability towards water in the pH range 3–10. MOF 1‐Eu is a promising luminescent probe for sensing Fe³⁺ in aqueous solution and is also selective towards rhodamine B (RhB) with a superior adsorption capacity of 735 mg g^?1, which is the highest among the reported Ln‐MOFs for RhB removal so far. Periodic DFT calculations further confirmed the selective adsorption of rhodamine B over other dyes.     

Triazine‐Cored Lanthanide‐Based Metal–Organic Frameworks Featuring Unique Water Chains and Strong Characteristic Emissions

A new triazine‐cored tricarboxylic acid, N,N′,N“‐1,3,5‐triazine‐2,4,6‐triyltris(cis‐4‐aminocyclohexane‐carboxylic acid) (H₃L), has been prepared by replacing the chlorine atoms of cyanuric chloride with cis‐4‐aminocyclohexane‐carboxylic acid, which has been used for the construction of a series of triazine‐cored lanthanide‐based metal–organic frameworks (MOFs). All these MOFs were structurally authenticated, revealing that they are isostructural and exist as two‐dimensional (2D) coordination networks with the general formula [Ln(L)(H₂O)₂]?5.5 H₂O (Ln= 1?Gd , 2?Tb , 3?Eu ). A unique one‐dimensional water chain, composed of primary tetrameric cyclic rings and dodecameric cyclic rings, has been found entrapped in the lattice. Moreover, all these compounds display bright characteristic photoluminescence. Particularly, for 1 , apart from the strong blue emission peak (Φ_f=20.6 %) corresponding to the intraligand transition under near‐UV excitation, the characteristic emissions of Gd³⁺ cation (Φ_f=5.0 %) were unexpectedly observed upon excitation at 273 nm.     

Highly Selective Water Adsorption in a Lanthanum Metal–Organic Framework

We present a new metal–organic framework (MOF) built from lanthanum and pyrazine‐2,5‐dicarboxylate (pyzdc) ions. This MOF, [La(pyzdc)_1.5(H₂O)₂] ? 2 H₂O, is microporous, with 1D channels that easily accommodate water molecules. Its framework is highly robust to dehydration/hydration cycles. Unusually for a MOF, it also features a high hydrothermal stability. This makes it an ideal candidate for air drying as well as for separating water/alcohol mixtures. The ability of the activated MOF to adsorb water selectively was evaluated by means of thermogravimetric analysis, powder and single‐crystal X‐ray diffraction and adsorption studies, indicating a maximum uptake of 1.2 mmol g^?1 MOF. These results are in agreement with the microporous structure, which permits only water molecules to enter the channels (alcohols, including methanol, are simply too large). Transient breakthrough simulations using water/methanol mixtures confirm that such mixtures can be separated cleanly using this new MOF.     

Dual‐Emission Luminescence of Magnesium Coordination Polymers Based on Mixed Organic Ligands

Presented herein are two luminescent magnesium coordination polymers (Mg‐CPs), namely [Mg₂(H₂O)₂(2‐NDC)₄(1,10‐phen)₂] ( 1 ) and [Mg₂(H₂O)(1,4‐NDC)₂(1,10‐phen)] ( 2 ), in which 2‐NDCH=2‐naphthalenecarboxylic acid, 1,4‐NDCH₂=1,4‐naphthalene dicarboxylic acid, and 1,10‐phen=1,10‐phenanthroline. Based on the mixed ligands, the title compounds exhibit linker‐based photoluminescence (PL) properties thanks to the unique configuration of the Mg²⁺ ions. The two compounds show interesting dual emission on excitation of the different luminophores of the mixed linkers. In particular, the emissions of compound 2 could be tuned from green to yellow simply by varying the excitation energies. Furthermore, 2 could be excited by using a commercial λ=450 nm blue LED chip to generate white‐light emission, which allows the fabrication of a white‐light‐emitting diode (WLED) with 20 lm W^?1 luminous efficacy. This work may provide a new method for designing tunable PL CPs by using the low‐cost and abundant magnesium ion.     

Ligand Functionalization in Metal–Organic Frameworks for Enhanced Carbon Dioxide Adsorption

Ligand functionalization in metal–organic frameworks (MOFs) has been studied extensively and has been demonstrated to enhance gas adsorption and induce interesting gas adsorption phenomena. This account summarizes our recent study of three series of MOFs by ligand functionalization, as well as their carbon dioxide adsorption properties. While ligand functionalization does not change the overall structure of the frameworks, it can influence their gas adsorption behavior. In the first two series, we show how ligand functionalization influences the CO₂ affinity and adsorption capacity of MOFs. We also show a special case in which subtle changes in ligand functionality alter the CO₂ adsorption profile.

     

Well‐Defined Metal–Organic Framework Hollow Nanocages

Metal–organic frameworks (MOFs) have demonstrated great potentials in a variety of important applications. To enhance the inherent properties and endow materials with multifunctionality, the rational design and synthesis of MOFs with nanoscale porosity and hollow feature is highly desired and remains a great challenge. In this work, the formation of a series of well‐defined MOF (MOF‐5, Fe^II‐MOF‐5, Fe^III‐MOF‐5) hollow nanocages by a facile solvothermal method, without any additional supporting template is reported. A surface‐energy‐driven mechanism may be responsible for the formation of hollow nanocages. The addition of pre‐synthesized poly(vinylpyrrolidone)‐ (PVP) capped noble‐metal nanoparticles into the synthetic system of MOF hollow nanocages yields the yolk–shell noble metal@MOF nanostructures. The present strategy to fabricate hollow and yolk–shell nanostructures is expected to open up exciting opportunities for developing a novel class of inorganic–organic hybrid functional nanomaterials.     

New 3 D Tubular Porous Structure of an Organic–Zincophosphite Framework with Interesting Gas Adsorption and Luminescence Properties

A new 3D tubular zinc phosphite, Zn₂(C₂₂H₂₂N₈)_0.5(HPO₃)₂?H₂O ( 1 ), incorporating a tetradentate organic ligand was synthesized under hydro(solvo)thermal conditions and structurally characterized by single‐crystal X‐ray diffraction. Compound 1 is the first example of inorganic zincophosphite chains being interlinked through 1,2,4,5‐tetrakis(imidazol‐1‐ylmethyl)benzene to form a tubular porous framework with unusual organic–inorganic hybrid channels. The thermal and chemical stabilities, high capacity for CO₂ adsorption compared to that for N₂ adsorption, and interesting optical properties of LED devices fabricated using this compound were also studied.     

Highly Selective Sorption and Luminescent Sensing of Small Molecules Demonstrated in a Multifunctional Lanthanide Microporous Metal–Organic Framework Containing 1D Honeycomb‐Type Channels

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.     

Structure‐Triggered High Quantum Yield Luminescence and Switchable Dielectric Properties in Manganese(II) Based Hybrid Compounds

Two new manganese(II) based organic–inorganic hybrid compounds, C₁₁H₂₁Cl₃MnN₂ ( 1 ) and C₁₁H₂₂Cl₄MnN₂ ( 2 ), with prominent photoluminescence and dielectric properties were synthesized by solvent modulation. Compound 1 with novel trigonal bipyramidal geometry exhibits bright red luminescence with a lifetime of 2.47 ms and high quantum yield of 35.8 %. Compound 2 with tetrahedral geometry displays intense long‐lived (1.54 ms) green light emission with higher quantum yield of 92.3 %, accompanied by reversible solid‐state phase transition at 170 K and a distinct switchable dielectric property. The better performance of 2 results from the structure, including a discrete organic cation moiety and inorganic metal anion framework, which gives the cations large freedom of motion.     

A Nanoscale Multiresponsive Luminescent Sensor Based on a Terbium(III) Metal–Organic Framework

A nanoscale terbium‐containing metal–organic framework ( nTbL ), with a layer‐like structure and [H₂NMe₂]⁺ cations located in the framework channels, was synthesized under hydrothermal conditions. The structure of the as‐prepared sample was systematically confirmed by powder XRD and elemental analysis; the morphology was characterized by field‐emission SEM and TEM. The photoluminescence studies revealed that rod‐like nTbL exhibited bright‐green emission, corresponding to ⁵D₄→⁷F_J (J=6–3) transitions of the Tb³⁺ ion under excitation. Further sensing measurements revealed that as‐prepared nTbL could be utilized as a multiresponsive luminescent sensor, which showed significant and exclusive detection ability for Fe³⁺ ions and phenylmethanol. These results highlight the practical applications of lanthanide‐containing metal–organic frameworks as fluorescent probes.     

Two‐Dimensional Co@N‐Carbon Nanocomposites Facilely Derived from Metal–Organic Framework Nanosheets for Efficient Bifunctional Electrocatalysis

Metal–organic frameworks (MOFs) and MOF‐derived nanomaterials have recently attracted great interest as highly efficient, non‐noble‐metal catalysts. In particular, two‐dimensional MOF nanosheet materials possess the advantages of both 2D layered nanomaterials and MOFs and are considered to be promising nanomaterials. Herein, we report a facile and scalable in situ hydrothermal synthesis of Co–hypoxanthine (HPA) MOF nanosheets, which were then directly carbonized to prepare uniform Co@N‐Carbon nanosheets for efficient bifunctional electrocatalytic hydrogen‐evolution reactions (HERs) and oxygen‐evolution reactions (OERs). The Co embedded in N‐doped carbon shows excellent and stable catalytic performance for bifunctional electrocatalytic OERs and HERs. For OERs, the overpotential of Co@N‐Carbon at 10 mA cm^?2 was 400 mV (vs. reversible hydrogen electrode, RHE). The current density of Co@N‐Carbon reached 100 mA cm^?2 at an overpotential of 560 mV, which showed much better performance than RuO₂; the largest current density of RuO₂ that could be reached was only 44 mA cm^?2. The Tafel slope of Co@N‐Carbon was 61 mV dec^?1, which is comparable to that of commercial RuO₂ (58 mV dec^?1). The excellent electrocatalytic properties can be attributed to the nanosheet structure and well‐dispersed carbon‐encapsulated Co, CoN nanoparticles, and N‐dopant sites, which provided high conductivity and a large number of accessible active sites. The results highlight the great potential of utilizing MOF nanosheet materials as promising templates for the preparation of 2D Co@N‐Carbon materials for electrocatalysis and will pave the way to the development of more efficient 2D nanomaterials for various catalytic applications.     

Nanocomposite Made of an Oligo(p‐phenylenevinylene)‐Based Trihybrid Thixotropic Metallo(organo)gel Comprising Nanoscale Metal–Organic Particles,Carbon Nanohorns,and Silver Nanoparticles

A silver ion (Ag⁺)‐triggered thixotropic metallo(organo)gel of p‐pyridyl‐appended oligo(p‐phenylenevinylene) derivatives (OPVs) is reported for the first time. Solubilization of single‐walled carbon nanohorns (SWCNHs) in solutions of the pure OPVs as well as in the metallogels mediated by π–π interactions has also been achieved. In situ fabrication of silver nanoparticles (AgNPs) in the SWCNH‐doped dihybrid gel leads to the formation of a trihybrid metallogel. The mechanical strength of the metallogels could be increased stepwise in the order: freshly prepared gel<dihybrid gel<trihybrid gel. Microscopic studies of the trihybrid gel indicate the formation of three distinct morphologies, that is, nanoscale metal–organic particles (NMOPs), flowerlike aggregates of SWCNHs and AgNPs, and also their integration with each other. Detailed studies suggest lamellar organizations of the linear metal–ligand complexes in the NMOPs, which upon association create a three‐dimensional network that eventually immobilizes the solvent molecules.