Hydrothermal Synthesis,Crystal Structure,and Luminescent Properties of Two Zinc(II) and Cadmium(II) 3D Metal‐­Organic Frameworks

Two zinc(II) and cadmium(II) metal‐organic frameworks with mixed ligands, {[Zn₂(biim‐4)₂(TDC)₂] · 2.5H₂O}_n ( 1 ) and {[Cd₂(biim‐4)₂(TDC)₂ · 2H₂O]}_n ( 2 ) [biim‐4 = 1,1′‐(1,4‐butanediyl)bis(imidazole); H₂TDC = thiophene‐2,5‐dicarboxylic acid], were hydrothermally synthesized. Both of them are characterized by elemental analysis, IR spectroscopy, and single crystal X‐ray diffraction. In 1 , the four‐connected Zn^II nodes are connected by four linear ligands extending into a 3D network, which further integrates a fivefold interpenetrating diamond 3D topological network and the free water molecules distribute in void space, whereas in 2 , the Cd^II ions are in a distorted octahedral arrangement linked by TDC^2– and biim‐4 ligands to construct a 3D framework. In topology analysis, C11 and C14 are simplified as 3‐connected nodes and the 3D framework displays a (3,5)‐connected net. Furthermore, the thermal and photoluminescent properties of 1 and 2 were also studied.     

Auxilary Ligand Directed Zinc(II) Metal‐Organic Frameworks with Different Topological Networks

By altering auxiliary N‐donor ligands, two Zn^II compounds, [Zn₃(HL)₂(4,4′‐bipy)₃]_n ( 1 ) and [Zn₄(L)₂(bpp)]_n ( 2 ) (H₄L = 3‐(2′,4′‐dicarboxylphenoxy)phthalic acid, 4,4′‐bipy = 4,4′‐bipyridine, and bpp = 1,3‐bis(4‐pyridyl)propane), were obtained under hydrothermal conditions. Structural analyses revealed that compound 1 features a trinodal (3,4,4)‐connected 3D topological framework, and compound 2 displays a (3,8)‐connected 3D pillar‐layered framework with a tfz‐d topology. Furthermore, the thermal stabilities and the luminescent properties of compounds 1 and 2 were investigated.     

Syntheses,Structures, and Magnetic Properties of Two Cobalt(II) Metal‐Organic Frameworks Based on Y‐shaped 3,5,4′‐Azobenzenetricarboxylic Acid and Different N‐donor Ligands

Two metal‐organic frameworks, [Co₂(ABTC)(bimh)(OH)] · 2H₂O ( 1 ) and [Co₃(ABTC)₂(dimb)₄]_n ( 2 ) [H₃ABTC = 3,4′,5‐azobenzenetricarboxylic acid, bimh = 1,1′‐(1,4‐hexanediy)bis(imidazole), dimb = 1,4‐bis(1H‐imidazol‐1‐yl)benzene], were prepared under solvothermal conditions and structurally characterized. Complex 1 demonstrates a complicated 3D (3,8)‐connected tfz‐d net with (4³)₂(4⁶.6¹⁷.8⁵) topology. The framework of 2 can be classified as a rare 3D (3,6,6)‐connected net with the Schäfli symbol of (4.6²)₂(4².6¹⁰.8³)(4⁴.6¹⁰.8), and exhibits an intriguing self‐penetrating motif. Meanwhile, the thermal stabilities and magnetic properties for 1 and 2 were also probed.     

Two 1,2,4‐Triazole‐based Zinc(II) Complexes with Aromatic Acid as Coligand: Synthesis,Structure and Fluorescence Properties

Two two‐dimensional (2‐D) trz‐based coordination polymers, {[Zn(trz)(mb)]·H₂O}_n ( 1 ) and {[Zn(trz)(ca)]·H₂O}_n ( 2 ) (Htrz = 1,2,4‐triazole, Hmb = 4‐methylbenzoic acid, and Hca = trans‐cinnamic acid), have been synthesized by diffusion method and fully structural characterized by elemental analysis, FT‐IR, single‐crystal X‐ray crystallography, TG and fluorescence spectra. Structural analysis reveals that both complexes exhibit the analogous 2‐D Zn^II‐trz layer motif with hydrophobic aromatic rings attached on both sides despite their different crystal system and space group (orthorhombic, Pbca for 1 and monoclinic, P2₁/c for 2 ). Interestingly, the discrete water‐dimer and infinite 1‐D water‐chain were observed to be entrapped in the 2‐D layer of 1 and 2 , respectively, resulted from the different orientation of lattice water molecules as well as the patterns of hydrogen bonds involved. In addition, their similiar thermal behaviors and fluorescence emissions originated from intraligand electronic transfer were also investigated and compared.     

Syntheses,Structures, and Luminescent Properties of two Cadmium(II) Entangled Frameworks Based on 5‐Bromoisophthalic Acid and Bipyridyl Ligands

Two cadmium(II) entangled frameworks, Cd(BIPA)(bpe)_1.5 ( 1 ) and Cd(BIPA)(bpp)(H₂O) ( 2 ), were prepared by hydrothermal reactions based on rigid 5‐bromoisophthalic acid (H₂BIPA) and two flexible bipyridyl ligands 1, 2‐bis(4‐pyridyl)ethane (bpe) and 1, 3‐bis(4‐pyridyl)propane (bpp). The complexes were characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, and single‐crystal X‐ray diffraction. Complex 1 is a rare example of a polycatenated array of 1D nanotubes, whereas complex 2 exhibits a three‐dimensional twofold interpenetrating diamondoid network. The analysis results reveal that the flexibility of the bipyridyl ligands plays a significant role in the structure of the final products. Moreover, the luminescent properties of the complexes were investigated.     

Two Manganese(II) Complexes with a Bulky Fluorene‐Based Carboxylate Ligand: Syntheses,Crystal Structures,and Luminescent Properties

To explore the coordination possibilities of fluorene‐based ligands, two manganese(II) complexes with the ligand 9,9‐dibutyl‐9H‐fluorene‐2,7‐carboxylate ( L ) were synthesized and characterized: [Mn₂( L )₂(DMF)₃]_∞ ( 1 ) and [Mn₂( L )₂(DMF)]_∞ ( 2 ). X‐ray single‐crystal diffraction analyses show that complex 1 has a two‐dimensional (2D) (4,4) structure, whereas complex 2 consits of a three‐dimensional (3D) (4,5)‐connected topology framework. The results indicate that the steric bulk of the fluorene ring in H₂ L plays an important role in the formations of 1 and 2 . Additional pyridine‐based ligands govern the formation of the final frameworks of 2 . Moreover, the luminescent properties of these complexes were briefly investigated.     

Synthesis,Structures, Magnetic and Luminescent Properties of a Series of Iron(II) and Zinc(II) Coordination Frameworks with Versatile 4‐Substitued 1, 2,4‐Triazole Ligands

Three multi‐dentate 1, 2,4‐triazole derivative ligands containing different 4‐substituted groups, namely N‐1, 2,4‐triazol‐4‐yl(pyridin‐3‐yl)methylenimine (L₁), N‐1, 2,4‐triazol‐ 4‐yl(pyridin‐4‐yl)methylenimine (L₂), and 4‐(2‐pyridine)‐1, 2,4‐triazole (L₃) were used to isolate five iron(II) and zinc(II) coordination frameworks, [Zn(μ₂‐L₁)Cl₂] ( 1 ), [Zn(μ₂‐L₂)Br₂] ( 2 ), [Fe(L₁)₂(NCS)₂(H₂O)₂] ( 3 ), [Fe(L₃)₂(dca)₂(H₂O)₂] ( 4 ), and [Fe(L₃)₂(μ₂‐dca)] ( 5 ) (dca = dicyanamide anion). When different zinc(II) salts were used to react with L₁ and L₂ under solvothermal conditions, two one‐dimensional (1D) zinc(II) coordination frameworks 1 and 2 containing four‐coordinate central zinc(II) atoms were isolated. 1 is a 3D achiral supra‐molecular framework, whereas 2 is a 3D chiral supra‐molecular framework containing helical chains on a 2₁ axis. 3 is a mono‐nuclear iron(II) coordination framework containing six‐coordinate central Fe^II atoms. When L₃ was employed, mono‐nuclear iron(II) framework 4 and 1D iron(II) chain 5 could be isolated when different amounts of Nadca were introduced into the reaction system. Variable‐temperature magnetic susceptibility data of 3 – 5 were recorded in the 2–300 K temperature range indicating weak anti‐ferromagnetic interactions. The solid‐state luminescent properties of coordination polymers 1 and 2 were also investigated at room temperature.     

Pore‐Environment Engineering in Multifunctional Metal‐Organic Frameworks

As a new type of highly ordered porous crystalline material, metal‐organic frameworks (MOFs) have been extensively studied in many fields due to their high specific surface area and porosity, flexible modifiability and tailorability. After nearly 20 years of development, the synthesis of MOF materials has gradually evolved from exploration and trial to precise design. The synthesis method has also evolved from an early one‐step synthesis to the coexistence of various synthesis strategies, including functional‐oriented microstructural design optimization, pore size adjustment, and secondary structural unit modification, enabling MOF materials to expand their potential applications in many fields. In this review, we mainly discuss the pore regulation of function‐oriented MOF through different synthesis strategies, including (1) direct synthesis, (2) post‐synthesis modification (PSM), (3) building block replacement (BBR), (4) pore space partition (PSP), (5) construction of multi‐mesoporous MOF, (6) dynamic septal ligand insertion, and discuss the relationship between related performance optimization through framework structure and pore environment/size optimization.     

Four Complexes with the Rigid Ligand 1,4‐Bis(1H‐imidazol‐4‐yl)benzene and Varied Carboxylate Ligands

Four metal‐organic coordination polymers [Co₂(L)₃(nipa)₂]·6H₂O ( 1 ), [Cd(L)(nipa)]·3H₂O ( 2 ), [Co(L) (Hoxba)₂] ( 3 ) and [Ni₂(L)₂(oxba)₂(H₂O)]·1.5L·3H₂O ( 4 ) were synthesized by reactions of the corresponding metal(II) salts with the rigid ligand 1,4‐bis(1H‐imidazol‐4‐yl)benzene (L) and different derivatives of 5‐nitroisophthalic acid (H₂nipa) and 4,4′‐oxybis(benzoic acid) (H₂oxba), respectively. The structures of the complexes were characterized by elemental analysis, FT‐IR spectroscopy and single‐crystal X‐ray diffraction. Complexes 1 and 3 have the same one‐dimensional (1D) chain while 2 is a 6‐connected twofold interpenetrating three‐dimensional (3D) network with α ‐Po 4¹²·6³ topology based on the binuclear Cd^II subunits. Compound 4 features a puckered two‐dimensional (2D) (4,4) network, and the large voids of the packing 2D nets have accommodated the uncoordinated L guest molecules. An abundant of N–H···O, O–H···O and C–H···O hydrogen bonding interactions exist in complexes 1–4 , which contributes to stabilize the crystal structure and extend the low‐dimensional entities into high‐dimensional frameworks. Lastly, the photoluminiscent properties of compounds 2 were also investigated.     

Syntheses,Structures and Characterization of Four Metal‐Organic Frameworks constructed by 2,2′,6,6′‐Tetramethoxy‐4,4′‐biphenyldicarboxylic Acid

Four metal‐organic frameworks (MOFs), {[Mn_3.5L(OH)(HCOO)₄(DMF)] · H₂O} ( 1 ), {[In_2.5L₂O(OH)_1.5(H₂O)₂] · DMF · CH₃CN · 2H₂O} ( 2 ), {[Pb₄L₃O(DMA)] · CH₃CN} ( 3 ), and {[LaL(NO₃)(DMF)₂] · 2H₂O} ( 4 ) were synthesized by utilizing the ligand 2,2′,6,6′‐tetramethoxy‐4,4′‐biphenyldicarboxylic acid (H₂L) via solvothermal methods. All MOFs were characterized by single‐crystal X‐ray diffraction, powder X‐ray diffraction, thermogravimetric analysis, and infrared spectroscopy. In 1 , the Mn²⁺ ions are interconnected by formic groups in situ produced via DMF decomposition to form a rare 2D macrocyclic plane, which is further linked by L^2– to construct the final 3D network. In 2 , 1D zip‐like infinite chain is formed and then interconnected to build the 3D framework. In 3 , a [Pb₆(μ₄‐O)₂(O₂C)₁₀(DMA)₂] cluster with a centrosymmetric [Pb₆(μ₄‐O)₂]⁸⁺ octahedral core is formed in the 3D structure. In 4 , the La³⁺ ions are connected with each other through carboxylate groups of L^2– to generate 1D zigzag chain, which is further linked by L^2– to construct a 3D network with sra topology. Solid photoluminescence properties of 3 and 4 were also investigated.     

Synthesis,Structure, Luminescent and Thermal Properties of Ytterbium(III) and Dysprosium(III) Complexes with 5‐Sulfoisophthalic Acid Sodium Salt

Two rare earth metal‐organic framework compounds [Ybsip(H₂O)₅] · 3H₂O ( 1 ) and [Dysip(H₂O)₄] ( 2 ) (NaH₂sip: 5‐sulfoisophthalic acid sodium salt) were synthesized hydrothermally, and characterized by single‐crystal X‐ray diffraction, elemental analysis, and FT‐IR spectroscopy. In complex 1 , each Yb^III atom is nine‐coordinate with a distorted monocapped tetragonal prismatic arrangement. Two carboxylate groups of each sip^3– molecule adopt the same μ₁‐η¹:η¹ chelating coordination model connecting two Yb^III atoms. The oxygen atoms of the sulfonate group do not participate in coordination with Yb^III. The whole sip^3– molecule acts as a μ₂ bridge to form an one‐dimensional (1D) chain structure. The 1D chains are linked by hydrogen bonding to generate two‐dimensional layers, and are further combined together to form a three‐dimensional structure. In complex 2 , the Dy^III atom is nine‐coordinate with a distorted monocapped tetragonal antiprismatic arrangement. In each sip^3– anion, two carboxylate groups take the same μ₁‐η¹:η¹ chelating coordination mode, only an oxygen atom of sulfonate group bond to Dy^III ion. The whole ligand sip^3– acts as a μ₃ bridge linking three different Dy^III ions to generate a wave‐like two‐dimensional network with (6,3) topological structure. The two‐dimensional networks are further linked by O–H ··· O hydrogen bonds to form a three‐dimensional structure. The thermal and luminescent properties of both complexes are investigated.     

Synthesis,Structures, and Luminescent Properties of Two Four‐connected Polymers Based on 2, 2‐Dimethylsuccinic Acid

The polymers [Cd(L)(H₂O)] ( 1 ) and [Zn(L)(4, 4′‐bipy)(H₂O)₃] ( 2 ) (L = 2, 2‐dimethylsuccinated anion) were synthesized under hydrothermal conditions and characterized by IR spectrosopy, elemental analyses, and single‐crystal X‐ray diffraction analysis. The latter reveals that the polymer 1 exhibits a four‐connected dia‐topology net based on the novel tetranuclear Cd^II units, whereas polymer 2 displays a 4‐connnected CdSO₄ topology net. Moreover, the photoluminescent properties of 1 and 2 were investigated.     

Syntheses,Crystal Structures,and Fluorescence Properties of Two Transition Metal‐Organic Coordination Polymers Based on 4,4′‐Dimethyl‐2,2′‐bipyridine

Two transition metal‐organic coordination polymers, [Mn₂(1,3‐bdc)₂(Me₂bpy)₂] · Me₂bpy ( 1 ) and [Co(4,4′‐oba)(Me₂bpy)] ( 2 ) were hydrothermally synthesized and structurally characterized by elemental analysis, IR spectroscopy, TG, and single‐crystal X‐ray diffraction [1,3‐H₂bdc = benzene‐1,3‐dicarboxylic acid, H₂oba = 4,4′‐oxybis(benzoic acid) Me₂bpy = 4,4′‐dimethyl‐2,2′‐bipyridine]. Compound 1 crystallizes in the orthorhombic system, space group P2₁2₁2₁, with a = 23.371(5), b = 14.419(3), and c = 14.251(3) Å. Compound 2 crystallizes in the monoclinic system, space group P2₁/c, with a = 7.4863(15), b = 18.272(4), c = 16.953(5) Å, and β = 107.44(3)°. The crystal structure of complex 1 is a wave‐like layer with central Mn²⁺ atoms bridged by 1,3‐bdc ligands, whereas the structure of compound 2 presents a ladder chain of hexacoordinate Co²⁺ atoms, in which the metal atoms are bridged by 4,4′‐oba ligands and decorated by Me₂bpy ligands. The two compounds are further extended into 3D supramolecular structures through π–π stacking interactions. Additionally, the compounds show intense fluorescence in solid state at room temperature.     

Six Coordination Polymers based on 4‐(1H‐Imidazol‐1‐yl)phthalic Acid: Structural Diversities,Magnetism and Luminescence Properties

The coordination polymers (CPs), [Ni(L)(H₂O)₄]_n ( 1 ), [Co(HL)₂(H₂O)₂]_n ( 2 ), {[Cu(L)(H₂O)₃] · H₂O}_n ( 3 ), [Mn(L)(H₂O)₂]_n ( 4 ), [Cd(L)(H₂O)₂]_n ( 5 ), and {[Zn₂(L)₂] · H₂O}_n ( 6 ), were solvothermally synthesized by employing the imidazol‐carboxyl bifunctional ligand 4‐(1H‐imidazol‐1‐yl) phthalic acid (H₂L). Single‐crystal X‐ray diffraction indicated that the L^2–/HL^– ligands display various coordination modes with different metal ions in 1 – 6 . Complexes 1 and 2 show one‐dimensional (1D) chain structures, whereas complexes 3 – 6 show 2D layered structures. The magnetic properties of these complexes were investigated. Complexes 1 and 3 indicate weak ferromagnetic interactions, whereas complexes 2 and 4 demonstrate antiferromagnetic interactions. In addition, luminescence properties of 5 and 6 were measured and studied in detail.     

Selenium‐Containing Heterocycles from Isoselenocyanates: Synthesis of 5‐Amino‐2,4‐dihydro‐3H‐1,2,4‐triazole‐3‐selones

The reaction of S‐methylisothiosemicarbazide hydroiodide (=S‐methyl hydrazinecarboximidothioate hydroiodide; 1 ), prepared from thiosemicarbazide by treatment with MeI in EtOH, and aryl isoselenocyanates 5 in CH₂Cl₂ affords 3H‐1,2,4‐triazole‐3‐selone derivatives 7 in good yield (Scheme 2, Table 1). During attempted crystallization, these products undergo an oxidative dimerization to give the corresponding bis(4H‐1,2,4‐triazol‐3‐yl) diselenides 11 (Scheme 3). The structure of 11a was established by X‐ray crystallography.     

An Isoreticular Family of Microporous Metal–Organic Frameworks Based on Zinc and 2‐Substituted Imidazolate‐4‐amide‐5‐imidate: Syntheses,Structures and Properties

We report on a new series of isoreticular frameworks based on zinc and 2‐substituted imidazolate‐4‐amide‐5‐imidate (IFP‐1–4, IFP=imidazolate framework Potsdam) that form one‐dimensional, microporous hexagonal channels. Varying R in the 2‐substitued linker (R=Me (IFP‐1), Cl (IFP‐2), Br (IFP‐3), Et (IFP‐4)) allowed the channel diameter (4.0–1.7 Å), the polarisability and functionality of the channel walls to be tuned. Frameworks IFP‐2, IFP‐3 and IFP‐4 are isostructural to previously reported IFP‐1. The structures of IFP‐2 and IFP‐3 were solved by X‐ray crystallographic analyses. The structure of IFP‐4 was determined by a combination of PXRD and structure modelling and was confirmed by IR spectroscopy and ¹H MAS and ¹³C CP‐MAS NMR spectroscopy. All IFPs showed high thermal stability (345–400 °C); IFP‐1 and IFP‐4 were stable in boiling water for 7 d. A detailed porosity analysis was performed on the basis of adsorption measurements by using various gases. The potential of the materials to undergo specific interactions with CO₂ was investigated by measuring the isosteric heats of adsorption. The capacity to adsorb CH₄ (at 298 K), CO₂ (at 298 K) and H₂ (at 77 K) at high pressure were also investigated. In situ IR spectroscopy showed that CO₂ is physisorbed on IFP‐1–4 under dry conditions and that both CO₂ and H₂O are physisorbed on IFP‐1 under moist conditions.     

Photoluminescence Properties of Lanthanide‐Organic Frameworks (LnOFs) with Thiophene‐2,5‐Dicarboxylate and Acetate

S‐heterocyclic dicarboxylic acid, thiophene‐2,5‐dicarboxylic acid (H₂TDC), was employed to construct a series of lanthanide‐organic frameworks (LnOFs) with coligand acetate, formulated as [Ln(TDC)(OAc)(H₂O)]_n [Ln = Eu ( 1 ), Tb ( 2 ), Gd ( 3 ), Dy ( 4 ), Sm ( 5 )] under hydrothermal conditions. Structure analysis reveals that 1 – 5 have dinuclear 3D metal organic frameworks (MOFs), in which TDC^2– and OAc^– display (κ¹‐κ¹)‐(κ¹–κ¹)‐μ₄ and (κ²‐κ¹)‐μ₂ coordination fashions, respectively. The dehydrated products of all compounds show high thermal stability above 410 °C. As for 1 , 2 , 4 , and 5 , the photoluminescence analyses exhibit characteristic luminescence emission bands of the corresponding lanthanide ions in the visible region. In particular, compound 2 displays bright green luminescence in the solid state with ⁵D₄ lifetime of 0.510 ms and relative high overall quantum yield of 16 %, based on an ideal energy gap between the lowest triplet state energy level of H₂TDC ligand and the ⁵D₄ state energy level of Tb³⁺. The energy transfer mechanisms in compounds 1 and 2 were also discussed.     

Two Three‐Dimensional Metal‐Organic Frameworks Constructed from Alkaline Earth Metal Cations (Sr and Ba) and 5‐Nitroisophthalicacid – Synthesis,Charaterization, and Thermochemistry

Two MOFs of [Sr^II(5‐NO₂‐BDC)(H₂O)₆] ( 1 ) and [Ba^II(5‐NO₂‐BDC)(H₂O)₆] ( 2 ) have been synthesized in water using alkaline earth metal salts and the rigid organic ligand 5‐NO₂‐H₂BDC. The compounds were characterized by elemental analysis, infrared spectrum, thermal analysis, and X‐ray crystallography. Crystal structure analyses have shown that the two complexes are isostructural as evidenced by IR spectra and TG‐DTA. Both compounds present three‐dimensional frameworks built up from infinite chains of edge‐sharing twelve‐membered rings through O–H···O hydrogen bonds. The specific heat capacities of the title complexes have been determined by an improved RD496‐III microcalorimeter with the values of (109.29 ± 0.693) J mol⁻¹ K⁻¹ and (81.162 ± 0.858) J mol⁻¹ K⁻¹ at 298.15 K, and the molar enthalpy changes of the formation reactions of complexes at 298.15 K were calculated as (4.897 ± 0.008) kJ mol⁻¹ and (2.617 ± 0.009) kJ mol⁻¹, respectively.     

A 2D Metal‐Organic Framework Based on 9‐(Pyridin‐4‐yl)‐9H‐carbazole‐3,6‐dicarboxylic Acid: Synthesis,Structure and Properties

A metal‐organic framework (MOF ) formulated as [Cd₂(μ₃‐L)₂(DMF )₄]•H₂O ( CdL ) [H₂L =9‐(pyridin‐4‐yl)‐ 9H ‐carbazole‐3,6‐dicarboxylic acid, DMF =N ,N ‐dimethylformamide] was synthesized under solvothermal condition. Crystal structural analysis reveals that CdL features the layered 2D framework with L^{2 −} ligands as 3‐connected nodes. The compound CdL emits blue‐violet light with the narrow emission peak and the emission maximum at 414 nm upon excitation at the maximum excitation wavelength of 340 nm. The compound CdL has a similar emission spectrum curve to the free H₂L ligand that indicates the emission of compound CdL should be originated from the coordinated L^{2 −} ligands.