Insight into the Construction of (3,6)-Connected rtl, ant, and Chiral anh Nets Based on Structural Investigation of Several MOFs via Steric Tuning of Linkers

Finely Tuning Metal Ion Valences of [Fe3-xMx(μ3-OH)(Carboxyl)6(pyridyl)2] Cluster-Based ant-MOFs for Highly Improved CO2 Capture Performances

Solvothermal reactions of different trinuclear precursors and 5-(pyridin-4-yl)isophthalic acid (H2L) successfully led to four anionic ant topological MOFs as Fe3-xMx(μ3-OH)(CH3COO)2(L)2·(DMA+)·DMF [M = Mn(II), Fe(II), Co(II), x = 0, 1, 2 and 3], namely, NJTU-Bai79 [NJTU-Bai = Nanjing Tech University Bai's group, Mn3(μ3-OH)], NJTU-Bai80 [Fe2Mn(μ3-OH)], NJTU-Bai81 [Fe3(μ3-OH)], and NJTU-Bai82 [Fe2Co(μ3-OH)], which possess the narrow pores (2.5-6.0 Å). NJTU-Bai80-82 is able to be tuned to the neutral derivatives [NJTU-Bai80-82(-ox), ox = oxidized] with M2+ ions oxidized to M3+ ones in the air and the OH- ions coordinated on M3+ ions. Very interestingly, selective CO2/N2 adsorptions of NJTU-Bai80-82(-ox) are significantly enhanced with the CO2 adsorption uptakes more than about 6 times that of NJTU-Bai79. GCMC simulations further revealed that neutral NJTU-Bai80-82(-ox) supplies more open frameworks around the -CH3 groups at separate spaces to the CO2 gas molecules with relatively more pores available to them after the removal of counterions. For the first time, finely tuning metal ion valences of metal clusters of ionic MOFs and making them from electrostatic to neutral were adopted for greatly improving their CO2 capture properties, and it would provide another promising strategy for the exploration of high-performance CO2 capture materials.

A pH-Stable Tb-MOF as Luminescence Sensor for Highly Sensitive Detection of Amino Acids through Diverse Sensing Mechanism

A luminescent Tb-MOF with excellent stability and dual-emitting properties was constructed with an amide-functionalized tetracarboxylate ligand. Tb-MOFs were initially assembled on one-dimensional Tb3+ chains, then formed a two-dimensional double-decker layer through the synergistic linking of organic ligands and bridging formic acid anions, and further fabricated the final three-dimensional structure through the connection of the organic ligands. Powder X-ray diffraction experiments revealed that Tb-MOFs not only exhibited excellent stability in water but also maintained structural integrity in the pH range of 2-12. Importantly, this Tb-MOF provided the first example of a metal-organic framework (MOF)-based luminescence sensor that can simultaneously detect two acid amino acids (aspartic and glutamic acids) through a turn-off sensing mechanism and two basic amino acids (lysine and arginine acids) through unusual turn-on and turn-off-on sensing mechanisms. Moreover, high sensitivity, low detection limit, and excellent recyclability of this sensor endow Tb-MOFs with great potential as a highly efficient amino acid fluorescence sensor in chemical detection and biological environments.

Multi-responsive luminescent sensitivities of two pillared-layer frameworks towards nitroaromatics, Cr2O72-, MnO4- and PO43- anions

Combining Zn(II) with two dicarboxylic acids of different length and functional groups results in the 2D metal-carboxylate layer of different size and shape, which are further connected by the same bis-pyridyl-bis-amide pillar to afford two 4-fold and 3-fold interpenetrating pillared-layer networks (1 and 2). Luminescent properties of 1 and 2 have been systematically investigated and demonstrated multi-responsive luminescent sensitivities. 1 can be used for highly sensitive detection of nitroaromatics. In particular, 2 can be used turn-off sensing towards Cr₂O₇^2- and MnO₄^- anions as well as turn-on sensing towards PO₄^3- anion in aqueous solution with high sensitivity and remarkable recyclability. The sensing mechanism is also discussed.

Pore-Space Partition through an Embedding Metal-Carboxylate Chain-Induced Topology Upgrade Strategy for the Separation of Acetylene/Ethylene

Ethylene (C₂H₄) is one of the most significant substances in the petrochemical industry; however, the capture of acetylene (C₂H₂) in about 1% from C₂H₂/C₂H₄ mixtures is a difficult task because of the similarity of their physical properties. With the aggravation of the energy crisis, using metal-organic framework (MOF) materials to purify C₂H₄ through adsorptive separation is a promising way to save energy and reduce emission. Pore-space partition (PSP) with the aim of enhancing the density of the binding sites and the strength of the host-guest interactions is an effective means to promote a solution for the challenging gas separation problems. Herein, we report a new embedding metal-carboxylate chain-induced topology upgrade strategy within a MOF to realize PSP and separation of C₂H₂/C₂H₄ mixtures. As a proof of concept, we construct a microporous MOF (NUM-12) utilizing the in situ insertion of cobalt terephthalic chains into a pretargeted ant-type framework during synthesis. Because of the attainment of an elaborately tuned aperture size and a specific pore environment through this strategy, NUM-12a (activated NUM-12) not only has a remarkable gas sorption capacity and strong interactions for C₂H₂ but also possesses an excellent purification performance for C₂H₂/C₂H₄ mixtures. Both experiments and simulation calculations clearly reveal that NUM-12 is a promising candidate for the separation of C₂H₂/C₂H₄, proving the feasibility of this new strategy for developing newly fashioned MOFs with adjustable structure and performance.

A dye encapsulated zinc-based metal-organic framework as a dual-emission sensor for highly sensitive detection of antibiotics

Self-assembly of two Zn-MOFs, [Zn₂L(DMF)₃]·H₂O·5DMF (1) and [Zn₂L(H₂O)₂]·4H₂O·3DMF (2), was achieved with an amide-functionalized tetracarboxylate ligand under similar conditions. Incorporated amide groups make the tetratopic linkers exhibit different configurations, tetrahedron and square, and subsequently combine tetrahedral [Zn₂(CO₂)₄] clusters or square paddle-well [Zn₂(CO₂)₄] clusters to afford a lon net for 1 and a nbo net for 2. Remarkably, 2 demonstrated high porosity and amide group decorated cages, and thereby proved to be a good capturing agent for a fluorescent dye molecule (DMASM). Consequently, a dual-emitting DMASM@2 sensor was successfully fabricated based on effective energy transfer from the host framework to DMASM with the variable luminescent color being visible to the naked eye. DMASM@2 could be used for the detection of metronidazole (MDZ) and dimetridazole (DTZ) with high sensitivity and remarkable recyclability.

Construction and selective gas adsorption properties of two heteroSBU MOFs based on unsymmetrical tetracarboxylate linkers

Two homometallic pure-carboxylate hetero-SBU MOFs were constructed, displaying selective C₂H₂/CH₄ and CO₂/CH₄ separation potential.

A multifunctional Cd(ii)-based metal–organic framework with amide groups exhibiting luminescence sensing towards multiple substances

By incorporating flexible amide group onto skeleton of a tetracarboxylate linker endows it with potential to serve as tetrahedral node and facilitate the construction of a flu net, which significantly demonstrates multi-responsive behavior.