Syntheses and High Proton Conductivities of Two 3D Zr(IV)/Hf(IV)-MOFs from Furandicarboxylic Acid

With the gradual progress of research on proton-conducting metal-organic framework (MOFs), it has become a challenging task to find MOF materials that are easy to prepare and have low toxicity, high stability, and splendid proton conductivity. With the abovementioned objectives in mind, we selected the non-toxic organic ligand 2,5-furandicarboxylic acid and the low toxic quadrivalent metals zirconium(IV) or hafnium(IV) as starting materials and successfully obtained 2 three-dimensional porous MOFs, [M6O4(OH)4(FDC)4(OH)4(H2O)4] [M = ZrIV (1) and HfIV (2)], with ultrahigh water stability using a rapid and green synthesis approach. Their proton conductive ability is remarkable, thanks to the large number of Lewis acidic sites contained in their porous frameworks and the abundant H-bonding network, hydroxyl groups, as well as coordination and crystalline water molecules. The positive correlation of their proton conductivity with relative humidity (RH) and the temperature was observed. Notably, their optimized proton conductivities are 2.80 × 10-3 S·cm-1 of 1 and 3.38 × 10-3 S·cm-1 of 2 under 100 °C/98% RH, which are at the forefront of Zr(IV)/Hf(IV) MOFs with prominent proton conductivity. Logically, their framework features, nitrogen/water adsorption/desorption data, and activation energy values are integrated to deduce their proton conductivity and conducting mechanism differences.

Application of MOFs and natural clays for removal of MCPD and GEs from edible oils

The aim of this study was to investigate the removal of 3-monochloropropane-1,2-diol (3-MCPD) and glycidyl esters (GEs) from edible oils by using Metal Organic Frameworks (MOF) and natural clays. First, the model oil was treated with adsorbents and titanium (IV) butoxide-terephthalate MOF (Ti-MOF) and kaolin were selected as the best performing MOF along with natural clay, respectively, for the removal of 3-MCPD and GEs. The effects of treatment conditions were also investigated, 6.0% adsorbent level, 120 min treatment time and 95 ºC temperature were determined to be the best treatment parameters. Finally, palm oil samples were treated with Ti-MOF and kaolin under the selected conditions and removal of 3-MCPD and GEs was obtained at up to 27% and 58%, respectively. In conclusion, MOFs and natural clays showed good potential for the removal of 3-MCPD and GEs, and the efficiency of the treatment can be improved by modifying the adsorbents.

Uncommon 3D Twofold Interpenetrated Zinc Phosphate Consisting of Inorganic Chains and Mixed Ligands for Highly Efficient Dye Removal Ability Using Its Nanosized Particles

The flexible blocks are the primary building units for constructing crystalline solids with interpenetrating structures. Herein, we reported a novel class of crystalline material with such structural features, which was made of two tetradentate ligands and one-dimensional (1D) rigid chains of zinc phosphate. This is also the first example of transition metal phosphate incorporating a squarate linker. Furthermore, efficient dye removal ability has been presented.

Cu(II) Coordination Complex: Anti-Thyroid Carcinoma Activity by Initiating Reactive Oxygen Species Accumulation and Inducing Cell Apoptosis

A mixed-donor ligand that shows pyrazole and carboxylic groups and a coordination complex that include Cu(II) has been created in the present study by mixing Hcppp with Cu(NO3)2 ·3H2O in water and DMF mixed solvent. The chemical formula of the compound is [Cu2(cppp)2(Hcppp)2(H2O)2] ·2NO3 ·6H2O. Additionally, Complex 1’s inhibitory influence against the cell proliferation of K1 human thyroid carcinoma cells was explored via exploiting the Cell Counting Kit-8 analysis. Annexin V-FITC/PI double staining analysis was finished to evaluate Complex 1’s mechanism, which induced the death of K1thyroid carcinoma cells. Moreover, the reactive oxygen species (ROS) analysis was implemented to determine the accumulation of ROS in K1 thyroid carcinoma cells.

Sodalite Cd66-Cage-Based Metal-Organic Framework Constructed by Cd9 and Cd5 Metal-Organic Clusters

A sodalite Cd₆₆-cage-based metal-organic framework (MOF), namely, CPM-9S, has been constructed based on Cd₉ and Cd₅ metal-organic clusters (MOCs), which, to the best our knowledge, represents the first Cd-cage-based MOF that contains the highest-nuclear Cd-based MOC and the largest number of Cd²⁺ ions in a cage. The iodine adsorption performances in terms of the iodine adsorption capacity, adsorption isotherm, and adsorption kinetics, as well as the adsorption mechanism, have been further studied.

Different Chemical Environments of [Ge4Se10]4- in the Li+ Compounds [Li4(H2O)16][Ge4Se10]·4.33H2O, [{Li4(thf)12}Ge4Se10], and [Li2(H2O)8][MnGe4Se10], and Ionic Conductivity of Underlying "Li4Ge4Se10"

The crystalline selenido germanates [Li₄(H₂O)₁₆][Ge₄Se₁₀]·4.3H₂O (1), [{Li₄(thf)₁₂}Ge₄Se₁₀] (2), and [Li₂(H₂O)₈][MnGe₄Se₁₀] (3) (thf = THF = tetrahydrofuran) were obtained by an extraction of a glassy ternary phase of the nominal composition Li₄Ge₄Se₁₀ (=Li₂S·2GeSe₂) with water (1) or THF (2) and slow evaporation of the solvent or by being layered with MnBr₂ in H₂O/MeOH (3), respectively. The compounds contain known selenido germanate anions, however, for the first time with Li⁺ counterions. This is especially remarkable for the prominent _∞³{[MnGe₄Se₁₀]^2-} open-framework structure, which was reported to crystallize with (NMe₄)⁺, Cs⁺, Rb⁺, and K⁺ counterions, but it has not yet been realized with the smallest alkali metal cation. Impedance spectroscopic studies on Li₄Ge₄Se₁₀ classify the glassy solid as a moderate Li⁺ ion conductor.

Equi-size nesting of Platonic and Archimedean metal-organic polyhedra into a twin capsid

Inspired by the structures of virus capsids, chemists have long pursued the synthesis of their artificial molecular counterparts through self–assembly. Building nanoscale hierarchical structures to simulate double-shell virus capsids is believed to be a daunting challenge in supramolecular chemistry. Here, we report a double-shell cage wherein two independent metal–organic polyhedra featuring Platonic and Archimedean solids are nested together. The inner (3.2 nm) and outer (3.3 nm) shells do not follow the traditional “small vs. large” pattern, but are basically of the same size. Furthermore, the assembly of the inner and outer shells is based on supramolecular recognition, a behavior analogous to the assembly principle found in double-shell viruses. These two unique nested characteristics provide a new model for Matryoshka–type assemblies. The inner cage can be isolated individually and proves to be a potential molecular receptor to selectively trap guest molecules.

Supramolecular constructs that mimic complex biological assemblies are synthetically challenging. Here, the authors present a double-shell cage wherein two independent metal-organic polyhedra are nested together in a manner analogous to that found in double-shell virus capsids.

A 116-Nuclear Metallosupramolecular Cage-of-Cage Showing Multistep Single-Crystal-to-Single-Crystal Transformation

Here a unique single-crystal-to-single-crystal (SCSC) transformation of a 116-nuclear Au^I ₇₂ Cd^II ₄₀ Na^I ₄ cage-of-cage (2_CdNa ) is reported, which was created from a trigold(I) metalloligand with d-penicillamine by way of a 9-nuclear Au^I ₆ Cd^II ₃ cage (1). Cage-of-cage 2_CdNa is composed of 12 cages of 1 that are linked by 4 Cd²⁺ and 4 Na⁺ ions, with its surface being covered by 12 NO₃ ^- ions to form a discrete, spherical molecule with a diameter ca. 4.7 nm. In crystal 2_CdNa , the cage-of-cage molecules are packed in a cubic lattice with a huge cell volume of ca. 4.5×10⁵  ų _, so as to have large interstices with diameters of more than 3 nm. Upon soaking crystals 2_CdNa in aqueous Cu(NO₃ )₂ , all Cd²⁺ and Na⁺ were quickly exchanged by Cu²⁺ to produce an analogous Au^I ₇₂ Cu^II ₄₄ cage-of-cage (2_Cu ) in a SCSC manner. Prolonged soaking led to the SCSC transformation to another supramolecular structure (2'_Cu ) consisting of 152-nuclear Au^I ₇₂ Cu^II ₈₀ cage-of-cages that are alternately H-bonded with the Au^I ₇₂ Cu^II ₄₄ cage-of-cages. 2'_Cu showed the accommodation of MoO₄ ^2- and the conversion of MoO₄ ^2- to β-Mo₈ O₂₆ ^4- in the crystal, with retention of single-crystallinity.

Cholesterol removal by selected metal-organic frameworks as adsorbents

The aim of this study was to investigate the cholesterol removal capacity of seven metal-organic frameworks (MOF) and to compare with active carbon as adsorbents, and with aqueous β-cyclodextrine complexation removal technique. There were slight color differences in the oil samples after the treatments. The lowest free fatty acidities (0.13% and 0.13% linoleic acid) and peroxide values (21.07 and 23.50 meqO₂/kg) were measured in aluminum-MOF (Al-MOF) and titanium-MOF (Ti-MOF) treated samples when compared to control sample (0.15%, and 27.62 meqO₂/kg). Cholesterol reduction ratios of the Al-MOF treated sample (27.45%) and Ti-MOF treated sample (26.27%) were higher among all adsorbent treatments, but lower than that of the β-cyclodextrine aqueous complexation technique (33.07%). Further experiments with Al-MOF and Ti-MOF showed that when adsorbent addition level increased to 3.0%, removed cholesterol content increased. Likewise, when treatment times extended to 180 min, more cholesterol was removed. But, the removed cholesterol contents at 100 °C and 30 °C treatment temperatures were lower than that of at 50 °C treatment temperature. Further experiments with butter and sheep tail tallow showed that Al-MOF was quite effective as an adsorbent to remove cholesterol. This study proves the great potential of MOF to remove cholesterol selectively from oil/fat by adsorption principle.

Purification of degummed crude sunflower oil with selected metal-organic frameworks as adsorbents

The aims of this study were to investigate the effectiveness of seven metal-organic frameworks (MOFs) as adsorbents for the purification of crude degummed sunflower oil, and to compare their effectiveness with three natural clays. The oil was treated with two different addition levels (0.05% and 0.3%, w/w), and two different treatment times (0.5 h and 3.0 h) under constant temperature (25 °C). The results indicated that all adsorbent treatments improved the oil’s physico-chemical properties. Most importantly, the oil’s free fatty acid, peroxide and p-anisidine values were significantly reduced by Ti-MOF and γ-CD-MOF in comparison with the control sample. The oil showed no contamination by the metals during the MOF treatments. There were no significant changes in the fatty acid or sterol composition of the treated oil, while α-tocopherol contents decreased to some extent. This study proved the possibility of MOF as adsorbents for crude oil purification, and showed the great potential of Ti-MOF and γ-CD-MOF as promising adsorbents.

A cluster-based mesoporous Ti-MOF with sodalite supercages

The cooperative assembly of a hexagonal column shaped [Ti₆O₆][ⁱPrO]₆⁶⁺ cluster and rhomboid Cu₂I₂ dimers using isonicotinic acid results in an unprecedented three-dimensional (3D) highly crystalline cluster-based Ti-MOF that features both giant sodalite cages with an inner diameter of 2.8 × 3.2 nm² and 3D open square channels.

Highly stable Y(iii)-based metal organic framework with two molecular building block for selective adsorption of C2H2 and CO2 over CH4

A novel microporous MOF ZJU-16 exhibited high thermal and chemical stability and moderately high selective separation of C₂H₂/CH₄ and CO₂/CH₄.

Enhancing the stability and porosity of penetrated metal-organic frameworks through the insertion of coordination sites

Guided by the insertion of coordination sites within ligands, an interpenetrated metal–organic framework (MOFs) NKU-112 and a self-penetrated framework NKU-113 were obtained. The enhanced stability and porosity of NKU-113 prove the efficiency of the method for the structure and properties modulation of penetrated MOFs.

Guided by the insertion of coordination sites within ligands, an interpenetrated metal–organic framework NKU-112 and a self-penetrated framework NKU-113 were obtained. The two MOFs have similar cage-based framework structures, while NKU-113 reveals enhanced porosity and stability compared with NKU-112, owing to the self-penetrated structure induced by the additional chelating bipyridine moiety in the ligand. To the best of our knowledge, this is the first study that attempts to shift the structure topology of a MOF from interpenetrated to self-penetrated while achieving a delicate modulation of the location and distances within the penetrated structure by inserting new coordination sites.

Pore Space Partition in Metal-Organic Frameworks

Metal-organic framework (MOF) materials have emerged as one of the favorite crystalline porous materials (CPM) because of their compositional and geometric tunability and many possible applications. In efforts to develop better MOFs for gas storage and separation, a number of strategies including creation of open metal sites and implantation of Lewis base sites have been used to tune host-guest interactions. In addition to these chemical factors, the geometric features such as pore size and shape, surface area, and pore volume also play important roles in sorption energetics and uptake capacity. For efficient capture of small gas molecules such as carbon dioxide under ambient conditions, large surface area or high pore volume are often not needed. Instead, maximizing host-guest interactions or the density of binding sites by encaging gas molecules in snug pockets of pore space can be a fruitful approach. To put this concept into practice, the pore space partition (PSP) concept has been proposed and has achieved a great experimental success. In this account, we will highlight many efforts to implement PSP in MOFs and impact of PSP on gas uptake performance. In the synthetic design of PSP, it is helpful to distinguish between factors that contribute to the framework formation and factors that serve the purpose of PSP. Because of the need for complementary structural roles, the synthesis of MOFs with PSP often involves multicomponent systems including mixed ligands, mixed inorganic nodes, or both. It is possible to accomplish both framework formation and PSP with a single type of polyfunctional ligands that use some functional groups (called framework-forming group) for framework formation and the remaining functional groups (called pore-partition group) for PSP. Alternatively, framework formation and PSP can be shouldered by different chemical species. For example, in a mixed-ligand system, one ligand (called framework-forming agent) can play the role of the framework formation while the other type of ligand (called pore-partition agent) can assume the role of PSP. PSP is sensitive to the types of inorganic secondary building units (SBUs). The coexistence of SBUs complementary in charge, connectivity, and so on can promote PSP. The use of heterometallic systems can promote the diversity of SBUs coexistent under a given condition. Heterometallic system with metal ions of different oxidation states also provides the charge tunability of SBUs and the overall framework, providing an additional level of control in self-assembly and ultimately in the materials' properties. Of particular interest is the PSP in MIL-88 type (acs-type topology) structure, which has led to a huge family of CPMs (called pacs CPMs, pacs = partitioned acs) exhibiting low isosteric heat of adsorption and yet superior CO₂ uptake capacity.

An enhanced extended hook method to realize tetranuclear metal clusters embedded in energetic metal–organic framework channels

Rare tetranuclear Zn clusters were successfully embedded into energetic 3D metal–organic framework channels by an extended bifunctional tetrazolate–carboxylate hook ligand.

Selectivity of CO2via pore space partition in zeolitic boron imidazolate frameworks

Co-assembly between boron imidazolate ligands and bridging dicarboxylate ligands with metal centers leads to pore space partitioning in two distinct BIFs with zeotype GIS (BIF-41) and ABW (BIF-42) topologies, respectively. BIF-41 shows high selectivity sorption of CO₂ over N₂.

An anionic zeolite-like metal–organic framework (AZMOF) with a Moravia network for organic dye absorption through cation-exchange

We have synthesized a new anionic zeolite-like metal–organic framework (AZMOF) with a twisted partially augmentedthenet, known as the “Moravia” net which is able to selectively adsorb organic cationic dyes (BR, RB, CV and MB) through cation-exchange.

Introduction of functionality, selection of topology, and enhancement of gas adsorption in multivariate metal-organic framework-177

Metal-organic framework-177 (MOF-177) is one of the most porous materials whose structure is composed of octahedral Zn4O(-COO)6 and triangular 1,3,5-benzenetribenzoate (BTB) units to make a three-dimensional extended network based on the qom topology. This topology violates a long-standing thesis where highly symmetric building units are expected to yield highly symmetric networks. In the case of octahedron and triangle combinations, MOFs based on pyrite (pyr) and rutile (rtl) nets were expected instead of qom. In this study, we have made 24 MOF-177 structures with different functional groups on the triangular BTB linker, having one or more functionalities. We find that the position of the functional groups on the BTB unit allows the selection for a specific net (qom, pyr, and rtl), and that mixing of functionalities (-H, -NH2, and -C4H4) is an important strategy for the incorporation of a specific functionality (-NO2) into MOF-177 where otherwise incorporation of such functionality would be difficult. Such mixing of functionalities to make multivariate MOF-177 structures leads to enhancement of hydrogen uptake by 25%.

Three luminescent metal–organic frameworks constructed from trinuclear zinc(ii) clusters and furan-2,5-dicarboxylate

Three metal–organic frameworks constructed from trinuclear zinc(ii) clusters and furan-2,5-dicarboxylate with different topology were hydrothermally synthesized by adjusting the anions and solvent. Moreover, the blue luminescence of the complexes was investigated.

Charge-tunable indium–organic frameworks built from cationic, anionic, and neutral building blocks

Three different indium building blocks, from a positive trimer to a negative monomer, lead to In-MOFs with tunable framework charge.

High-nuclearity silver(I) cluster-based coordination polymers assembled with multidentate oligo-α-heteroarylsulfanyl ligands

Two novel coordination polymers [Ag16(SO4)8][Ag4(SO4)2]3(L1)12·nH2O (n = 72) (1) and [Ag10(SO4)5(L2)4(H2O)2]·8H2O (2) based on conformationally variable oligo-α-heteroarylsulfanyl ligands 2-(pyrazin-2-ylthio)-6-(pyridin-2-ylthio)pyrazine (L1) or 2,6-bis(pyrazin-2-ylthio)pyrazine (L2) and sulfate-templated high-nuclearity Ag(I) clusters as structure-building units (SBUs) have been synthesized under mild conditions. Single-crystal X-ray analysis showed that complex 1 exhibits a porous three-dimensional framework containing Ag16(SO4)8 and Ag4(SO4)2 SBUs that are interconnected by L1 ligands, whereas 2 has a much denser network constructed from Ag10(SO4)5 SBUs and L2 linkers. To our knowledge, the Ag16(SO4)8 cluster core found in 1 is the largest sulfate-based polynuclear SBU in coordination polymers, and the 14-connected Ag10(SO4)5 in 2 is the highest-connectivity Ag(I) cluster SBU reported to date. These two complexes were fully characterized by infrared spectroscopy, elemental analysis, powder X-ray diffraction, thermogravimetric analysis and differential scanning calorimetry.

A porous sodalite-type MOF based on tetrazolcarboxylate ligands and [Cu4Cl]7+ squares with open metal sites for gas sorption

A porous sodalite-type metal-organic framework based on tetrazolcarboxylate ligands and [Cu4Cl](7+) squares was successfully synthesized, which exhibited permanent porosity and high adsorption abilities of H2, CO2 and organic chemical pollutants.