Double-Walled Zn36@Zn104 Multicomponent Senary Metal-Organic Polyhedral Framework and Its Isoreticular Evolution

One-Pot Synthesis of MOF@MOF: Structural Incompatibility Leads to Core-Shell Structure and Adaptability Control Makes the Sequence

Core-shell metal-organic frameworks (MOF@MOF) are promising materials with sophisticated structures that cannot only enhance the properties of MOFs but also endow them with new functions. The growth of isotopic lcore-shell MOFs is mostly limited to inconvenient stepwise seeding strategies with strict requirements, and by far one-pot synthesis is still of great challenge due to the interference of different components. Through two pairs of isoreticular MOFs, it reveals that the structural incompatibility is a prerequisite for the formation of MOFs@MOFs by one-pot synthesis, as illustrated by PMOF-3@HHU-9. It further unveils that the adaptability of the shell-MOF is a more key factor for nucleation kinetic control. MOFs with flexible linkers has comparably slower nucleation than MOFs with rigid linkers (forming PMOF-3@NJU-Bai21), and structural-flexible MOFs built by flexible linkers show the lowest nucleation and the most adaptability (affording NJU-Bai21@HHU-9). This degree of adaptability variation controls the sequence and further facilitates the synthesis of a first triple-layered core-shell MOF (PMOF-3@NJU-Bai21@HHU-9) by one-pot synthesis. The insight gained from this study will aid in the rational design and synthesis of other multi-shelled structures by one-pot synthesis and the further expansion of their applications.

Target Design of Multinary Metal-Organic Frameworks for Near-Infrared Imaging and Chemodynamic Therapy

Imaging-guided chemodynamic therapy is widely considered a promising modality for personalized and precision cancer treatment. Combining both imaging and chemodynamic functions in one system conventionally relies on the hybrid materials approach. However, the heterogeneous, ill-defined, and dissociative/disintegrative nature of the composites tends to complicate their action proceedings in biological environments and thus makes the treatment imprecise and ineffective. Herein, a strategy to employ two kinds of inorganic units with different functions─reactive oxygen species generation and characteristic emission─has achieved two single-crystalline metal-organic frameworks (MOFs), demonstrating the competency of reticular chemistry in creating multifunctional materials with atomic precision. The multinary MOFs could not only catalyze the transformation from H2O2 to hydroxyl radicals by utilizing the redox-active Cu-based units but also emit characteristic tissue-penetrating near-infrared luminescence brought by the Yb4 clusters in the scaffolds. Dual functions of MOF nanoparticles are further evidenced by pronounced cell imaging signals, elevated intracellular reactive oxygen species levels, significant cell apoptosis, and reduced cell viabilities when they are taken up by the HeLa cells. In vivo NIR imaging is demonstrated after the MOF nanoparticles are further functionalized. The independent yet interconnected modules in the intact MOFs could operate concurrently at the same cellular site, achieving a high spatiotemporal consistency. Overall, our work suggests a new method to effectively accommodate both imaging and therapy functions in one well-defined material for precise treatment.

Cucurbituril-Shaped Cd18(triazolate)12 Unit-Based Metal-Organic Framework Exhibiting an C2H2/CO2 Separation Ability

Herein, a metal-organic framework (MOF), {[(Me2NH2)4][Cd(H2O)6][Cd18(TrZ)12(TPD)15(DMF)6]}n (denoted as JXNU-18, TrZ = triazolate), constructed from the unique cucurbituril-shaped Cd18(TrZ)12 secondary building units bridged by 2,5-thiophenedicarboxylic (TPD2-) ligands, is presented. The formation of the cucurbituril-shaped Cd18(TrZ)12 unit is unprecedented, demonstrating the geometric compatibility of the organic linkers and the coordination configurations of the cadmium atoms. Each Cd18(TrZ)12 unit is connected to eight neighboring Cd18(TrZ)12 units through 30 TPD2- linkers, affording the three-dimensional structure of JXNU-18. More interesting is that JXNU-18 displays an efficient C2H2/CO2 separation ability, as revealed by the gas adsorption experiments and dynamic gas breakthrough experiments, which afford insights into the potential applications of JXNU-18 in gas separation. The tubular pores composed of two Cd18(TrZ)12 units bridged by six 2,5-thiophenedicarboxylic linkers provide the suitable pore space for C2H2 trapping, as unveiled by computational simulations.

Zn(II)-Siloxane Clusters as Versatile Building Blocks for Carboxylate-Based Metal-Organic Frameworks

Siloxanes have long been known for their highly desirable properties suited for a wide range of practical applications; however, their utilization as modular building blocks for crystalline open frameworks has been limited. In this study, a simple solvothermal pathway has been found to synthesize unprecedented Zn(II)-siloxane clusters supported by acetate ligands, [(RSiO2)8Zn8(CH3CO2)8] (R = Me or Ph). The same reaction using a dicarboxylate ligand such as 1,4-benzenedicarboxylate or 2,6-naphthalenedicarboxylate produces a new type of metal-organic framework, named SiMOF here, based on the [Si8Zn8] units. With the maximum connectivity of 8, the building block is shown to form topologically interesting structures such as octahedral supercages or uninodal 8-connected frameworks. All SiMOFs synthesized possess permanent porosity and high thermal stability and are naturally hydrophobic, as demonstrated by adsorptions of toluene, ethanol, methanol, and water vapor as well as water contact angle measurements. These promising characteristics for well-defined porous solids are attributed to metal-bound siloxane groups in the structural building units.

Rotation configuration control of the sp2 bond in the diimidazole-dicarboxylate linker for the isomerism of porous coordination polymers

Porous isomers constructed from the same building blocks but different topology break the general preferred coordination rule of organic linkers and metal nodes, representing an invaluable opportunity for enriching their pore chemistry. Herein, a new group of porous isomers (termed as NTU-69 and NTU-70) was prepared from a C_2v symmetric diimidazole-dicarboxylate ligand and mononuclear Cu ion. The structural differences arise from the different rotation configuration of the sp² bond in the ligand, leading them to exhibit completely different topologies of unc (NTU-69) and sod (NTU-70) as well as framework rigidness. This rotation configuration of the sp² bond can be controlled by the different acidity of the synthetic solution and the metal/ligand ratio. Gas adsorption and IAST selectivity show that NTU-70 features high potential for CH₄ purification from C₂H₄, C₂H₆, C₃H₆ and CO₂ mixtures at room temperature. The insight from this work establishes a new bridge between the ligand design and controlled construction of porous isomers.

Designing Multicomponent Metal-Organic Frameworks with Hierarchical Structure-Mimicking Distribution for High CO2 Capture Performance

By utilizing a mixed-ligand strategy, a novel multicomponent Cu-metal-organic framework (MOF) (JLU-MOF107) has been successfully synthesized. JLU-MOF107 has an unusual hierarchical structure-mimicking distribution structure. The triangular 4,4',4″-benzene-1,3,5-triyl-tribenzoate (BTB) ligand and the binuclear Cu cluster form a threefold interpenetration layer, while the linear ligand 1,4-phenylene-4,4'-bis(1,2,4-triazole) (p-tr₂ph) and tetranuclear Cu cluster form a noninterpenetration pillared-layer structure. Then, the two types of layers are connected by tetranuclear Cu clusters to construct the final sandwichlike framework. JLU-MOF107 exhibits good water and humidity stability. Due to the presence of various active sites and pores, JLU-MOF107 shows an outstanding performance for CO₂ capture (171.0 cm³ g^-1 at 273 K). Density functional theory (DFT)-based calculations further prove the interactions between CO₂ molecules and multiple active sites. The innovative synthesis of this multicomponent structure offers a new perspective on making hierarchical porous materials and multifunctional MOFs.

Mixed-Linker Strategy for the Construction of Metal-Organic Framework Combined with Dyes toward Alcohol Detection

Herein, a N-rich metal-organic framework (MOF) with four kinds of cages, Zn₄(ade)₂(TCA)₂(H₂O) (NENU-1000, Hade = adenine, H₃TCA = 4,4',4″-tricarboxytriphenylamine, NENU = Northeast Normal University), was prepared by the mixed-ligand strategy. Cationic dyes can be selectively absorbed by NENU-1000 at proper concentrations, but not neutral and anionic dyes, which perhaps can be assigned to the N-rich neutral framework of NENU-1000. When NENU-1000 was introduced to a relatively lower concentration of cationic dye solutions (e.g., rhodamine B or basic red 2), the colors of these systems faded quickly. Furthermore, the faded solutions can be used for the detection of methanol and other small alcohol molecules with either the naked eye or common UV-vis spectra. The effect of the length of carbon chain, the position of the -OH group, and the number of the hydroxyl group of the alcohols was explored for the color development rate. In addition, the performance of NENU-1000 in iodine sorption and release was also studied.