Highly Selective Separation of C₃H₈ and C₂H₂ from CH₄ within Two Water-Stable Zn₅ Cluster-Based Metal–Organic Frameworks

Adopting the mixed ligands approach, two water-stable Zn5 cluster-based MOFs, [Zn10(TZ)12(TADIPA)2(DMF)4]·DMF·6H2O (JLU-MOF66) and [Zn10(TZ)12(TPTA)2(DMA)2]·2DMA·4H2O (JLU-MOF67), have been constructed (H4TADIPA = 5,5′-(1H-1,2,4-triazole-3,5-diyl)­diisophthalic acid, H4TPTA = [1,1′:3′,1″-terphenyl]-3,3″,5,5″-tetracarboxylic acid, and HTZ = 1H-[1,2,3]­triazole). Both compounds with [Zn5(TZ)6] clusters exhibit extraordinary stability (pH = 2–11) and selectivity of C3H8/CH4 (308 for JLU-MOF66, and 287 for JLU-MOF67). Compared to JLU-MOF67, JLU-MOF66 with functional groups exhibits higher CO2 and C2H2 uptake capacity and excellent selective separation for C2H2/CH4 (86, 1:1). Such high separation and chemical stability render them as promising materials for industrial applications

Highly Selective Separation of C₃H₈ and C₂H₂ from CH₄ within Two Water-Stable Zn₅ Cluster-Based Metal–Organic Frameworks

Adopting the mixed ligands approach, two water-stable Zn5 cluster-based MOFs, [Zn10(TZ)12(TADIPA)2(DMF)4]·DMF·6H2O (JLU-MOF66) and [Zn10(TZ)12(TPTA)2(DMA)2]·2DMA·4H2O (JLU-MOF67), have been constructed (H4TADIPA = 5,5′-(1H-1,2,4-triazole-3,5-diyl)­diisophthalic acid, H4TPTA = [1,1′:3′,1″-terphenyl]-3,3″,5,5″-tetracarboxylic acid, and HTZ = 1H-[1,2,3]­triazole). Both compounds with [Zn5(TZ)6] clusters exhibit extraordinary stability (pH = 2–11) and selectivity of C3H8/CH4 (308 for JLU-MOF66, and 287 for JLU-MOF67). Compared to JLU-MOF67, JLU-MOF66 with functional groups exhibits higher CO2 and C2H2 uptake capacity and excellent selective separation for C2H2/CH4 (86, 1:1). Such high separation and chemical stability render them as promising materials for industrial applications

Hydrogen-Bond-Connected 2D Zn-LMOF with Fluorescent Sensing for Inorganic Pollutants and Nitro Aromatic Explosives in the Aqueous Phase

Herein, a novel luminescent Zn-LMOF, JLU-MOF109 ([Zn(PBBA)(H2O)]·3DMF·2H2O, PBBA = 4,4′-(2,6-pyrazinediyl)bis[benzoic acid], DMF = N,N-dimethylformamide), was successfully synthesized under solvothermal conditions. Zinc ions are connected by PBBA ligands to form two-dimensional (2D) layers, and the layers are further propped up through hydrogen-bonding interactions. JLU-MOF109 exhibits good sensitivity to inorganic pollutants, Fe3+ and Cr2O72–, as well as nitro aromatic explosives, 2,4,6-trinitrophenol and 2,4-dinitrophenol. JLU-MOF109 exhibits high Ksv (at 104 M–1 level) and low limit of detection values (∼10–6 mol/L) for the abovementioned hazardous pollutants, which is better than a majority of previously reported MOF-based fluorescent sensors. With good stability in the aqueous phase, JLU-MOF109 can serve as a promising chemical sensor for pollutant detection in wastewater

Exploring the Effect of Different Secondary Building Units as Lewis Acid Sites in MOF Materials for the CO₂ Cycloaddition Reaction

In order to explore the catalytic effect of different Lewis acid sites (LASs) in the CO2 cycloaddition reaction, different secondary building units and N-rich organic ligand 4,4′,4″-s-triazine-1,3,5-triyltri-p-aminobenzoate were assembled to construct six reported MOF materials: [Cu3(tatab)2(H2O)3]·8DMF·9H2O (1), [Cu3(tatab)2(H2O)3]·7.5H2O (2), [Zn4O(tatab)2]·3H2O·17DMF (3), [In3O(tatab)2(H2O)3](NO3)·15DMA (4), [Zr6O4(OH)7(tatab)(Htatab)3(H2O)3]·xGuest (5), and [Zr6O4(OH)4(tatab)4(H2O)3]·xGuest (6) (DMF = N,N-dimethylformamide, and DMA = N,N-dimethylacetamide). Large pore sizes of compound 2 enhance the concentration of substrates, and the multi-active sites inside its framework synergistically promote the process of the CO2 cycloaddition reaction. Such advantages endow compound 2 with the best catalytic performance among the six compounds and surpass many of the reported MOF-based catalysts. Meanwhile, the comparison of the catalytic efficiency indicated that Cu-paddlewheel and Zn4O display better catalytic performances than In3O and Zr6 cluster. The experiments investigate the catalytic effects of LAS types and prove that it is feasible to improve CO2 fixation property by introducing multi-active sites into MOFs

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

Two Robust Isoreticular Metal–Organic Frameworks with Different Interpenetration Degrees Exhibiting Disparate Breathing Behaviors

Herein, two robust isoreticular metal–organic frameworks (MOFs), ([Bi­(CPTTA)]·[Me2NH2]·2DMF) (JLU-MOF120, H4CPTTA = 5′-(4-carboxyphenyl)-[1,1′:3′,1″-terphenyl]-3,4″,5-tricarboxylic acid, DMF = N, N- dimethylformamide) and ([In­(CPTTA)]·[MeNH3]·2.5H2O·1.5NMF) (JLU-MOF121, NMF = N- methylformamide), with different interpenetration degrees were successfully constructed. According to the hard–soft acid–base (HSAB) theory, high-valent metal ions and carboxylate-based ligands were selected and formed twofold interpenetrated structures with saturated coordinated mononuclear second building units ([M­(COO)4], M = Bi, In). Owing to the features of the frameworks, JLU-MOF120 and JLU-MOF121 exhibited excellent stability, which could retain their integrity in water for at least 14 days and aqueous solutions with a pH range of 3–11 for at least 24 h. According to the structural regulation strategy, by changing the torsion angles of the ligand, the degrees of interpenetration for JLU-MOF120 and JLU-MOF121 were different, leading to various gate-opening pressures in CO2 at 195 K. Furthermore, JLU-MOF120 exhibits the scarce potential of C2H2/CO2 separation among Bi-MOF materials at 298 K under 101 kPa, JLU-MOF121 shows high CO2/CH4 selectivity under ambient conditions (11.7 for gas mixtures of 50 and 50% and 16.1 for gas mixtures of 5 and 95%). Moreover, owing to the flexibility of the structure, JLU-MOF121 possesses disparate breathing behaviors for C2H2 and C2H6 at 273 and 298 K, with the differences in uptakes among C2 hydrocarbons resulting in the potentiality of C2H4 purification. Overall, such HSAB theory and the structural regulation strategy could provide a valid method for constructing stable and flexible structures for the application in gas separation

Synthesis, Structure, and Gas Sorption Studies of a Three-Dimensional Metal−Organic Framework with NbO Topology

A new tetracarboxylate ligand with two alkyne functionalities has been synthesized and used to form a three-dimensional (3D) metal−organic framework {[Cu2(BDDC)(H2O)2]·DMF·3H2O}n (H4BDDC = 5,5′-(buta-diyne-1,4-diyl) diisophthalic acid) (DMF = N,N′-dimethylformamide). The single-crystal structure analysis reveals the topology is based on the NbO net, constructed by 4-connected rectangular ligands and 4-connected square Cu2(CO2)4 secondary building units (SBUs). The compound has permanent porosity with a large Langmuir surface area of 3111 m2/g, and shows excess and total H2 uptake as high as 3.98 and 4.60 wt %, respectively, at 77 K and 17 bar

Construction of Lanthanide–Organic Frameworks from 2-(pyridine-3-yl)-1<i>H</i>-4,5-imidazoledicarboxylate and Oxalate

Three novel isostructural lanthanide organic frameworks, |(H₂O)­(H₃O)|[Ln­(HPyImDC)­(OX)_0.5Cl] (Ln = Pr (<b>1</b>), Nd (<b>2</b>), and Sm (<b>3</b>), H₃PyImDC = 2-(pyridine-3-yl)-1<i>H</i>-4,5-imidazoledicarboxylic acid, H₂OX = oxalic acid) have been prepared under hydrothermal conditions and characterized by single crystal X-ray diffraction, elemental analysis, IR spectra, and thermogravimetric analysis. The results of crystal structural analysis indicate that three compounds are isomorphous 3D frameworks, which are constructed by lanthanide polyhedral {LnNClO₆}, 4-connected HPyImDC^2– ligand and bridging OX^2– ligand. The HPyImDC^2– ligand offering its four oxygen atoms and one nitrogen atom of the pyridyl group, and the OX^2– ligand offering all its four oxygen atoms coordinate with the lanthanide ions, which is a key essential for constructing the 3D frameworks. Topological analysis reveals that the 3D framework can be simplified into a 5-connected network with the lanthanide ion as a unique node, possessing the rare <b>sqp</b> topology. Meanwhile, the luminescent properties of three compounds in the solid state at room temperature are also investigated

Terminating Effects of Organosilane in the Formation of Silica Cross-Linked Micellar Core−Shell Nanoparticles

One advanced synthesis strategy for monodisperse silica cross-linked micellar core−shell nanoparticles (SCMCSNs) involves the use of organosilane termination agent RnSi(OR′)4 − n. In this study, we investigated the effects of the organosilane termination agent in the formation of SCMCSNs. Experimental data (synthesis results, 29Si MAS NMR, molecule probe fluorescence spectra, etc.) from a synthesis system with Pluronic F127 as the template indicate that organosilane either covers or reacts with the surface Si−OH groups of nanoparticles. The reduction of reactive surface Si−OH groups helps to stabilize nanoparticles by avoiding aggregation. The terminating behavior of organosilane is determined by its molecular structure, including (1) the value of n, (2) the length of hydrocarbon chain R, and (3) the charge of R. Effective organosilane termination agents are also applicable to other synthesis mixtures such as the systems using Si(OC2H4OH)4 as the silica source or F108 or Brij 700 as the template. Furthermore, we can obtain monodisperse nanoparticles by using the trisodium salt of triacetic acid N-(trimethoxysilylpropyl)ethylenediamine (TANED), which acts not only as a termination agent for the successful synthesis of SCMCSNs but also as a functional group to improve the performance of SCMCSNs in potential applications