Cluster-based Metal-organic Frameworks Research Articles

Preprocessed Monomer Interfacial Polymerization for Scalable Fabrication of High-Valent Cluster-Based Metal-Organic Framework Membranes.

Current research on emergent membrane materials with ordered and stable nanoporous structures often overlooks the vital facet of manufacturing scalability. We propose the preprocessed monomer interfacial polymerization (PMIP) strategy for the scalable fabrication of high-valent cluster-based metal-organic framework (MOF) membranes with robust structures. Using a roll-to-roll device on commercial polymer supports, Zr-fum-MOF membranes are continuously processed at room temperature through the PMIP approach. These large-area membranes demonstrate the preeminent hydrogen separation capabilities, boasting an order of magnitude of permeance and a thrice-enhanced selectivity when juxtaposed with conventional polymeric membranes. The obtained PMIP-Zr-fum-MOF membranes possess superior stability in water compared with interfacial polymerization (IP)-processed low-valent metal-ion-based ZIF-8 membranes. Moreover, we have implemented the PMIP strategy's universality to process the other four diverse MOF membranes. The proposal of PMIP significantly advances the scalable fabrication of water-stable high-valent cluster MOF membranes.

Efficient paddle-wheel copper cluster-based metal-organic framework for catalytic conversion of CO2 to oxazolidinones under mild conditions

Efficient utilization of CO2 and its conversion into high-value-added products contribute to mitigating environmental issues such as the greenhouse effect. Among these methods, the carboxylation cyclization of CO2 with propargylic amine represents a green and atom-economical approach. Developing cost-effective catalyst that can promote this reaction under mild condition is desirable but challenging. Herein, a unique two-dimensional (2D) metal–organic framework (MOF) {[Cu(QCA)2]∙0.5DMF∙0.5H2O}n (1) (QCA =6-quinolinecarboxylic acid, DMF = N,N-dimethylformamide) have been synthesized and thoroughly characterized. Compound 1 was constructed from paddle-wheel dinuclear copper clusters [Cu2(COO)4] and carboxylate ligands, presenting a two-dimensional framework with new topology. Stability tests indicate that compound 1 undergoes reversible structural changes in different solvents and exhibits good thermal stability. 1 as heterogeneous catalyst enabled the transformation of CO2 and propargylic amine into oxazolidinones under mild conditions with broad substrate generality. In addition, 1 could maintain its catalytic performance with five continuous reactions. This work presents an infrequent example of a 2D noble metal free MOF-based catalyst that shows high catalytic efficiency under mild conditions.

Halogen-Driven Single-Crystal to Single-Crystal Transformation Engineering the Cluster-based Spin Crossover Frameworks.

Cluster-based spin crossover (SCO) frameworks are a new class of smart metal-organic frameworks (MOFs) with diverse structures and topologies and unique bistable physicochemical properties. Here, we report a cluster-based SCO framework [Fe3{Ag4(CN)6(H2O)}2(TPBA)3](ClO4)2·7DMF (1) with an extremely rare 3,4,6-T108 topology, in which the tripodal [Ag{Ag(CN)2}3(H2O)]2- clusters axially link the Fe2+ ions to form 2D→3D n-fold Borromean entangled networks. Under the guidance of reticular chemistry, the post-synthetic modification (PSM) from 1 with 3,4,6-T108 topology to [Fe3{Ag8X8(CN)6}(TPBA)3] (2_X, X = Cl, Br, I) with urk topology is firstly achieved via single-crystal to single-crystal (SCSC) transformation. Moreover, the successive SCSC transformations from 2_Cl to 2_Br and then to 2_I are realized for the first time. Their SCO behaviors are also modified by halogen-driven stepwise cluster transformations. Hence, these findings provide new strategies for the development of cluster-based SCO MOFs towards the smart functional porous materials.

The effects of different functional groups in Ni3-cluster MOFs on the efficient capture and transformation for flue gas CO2

As the greenhouse effect continuous increasing, the efficient CO2 capture and conversion into high-value fine chemicals have been necessary and meaningful. However, the CO2 coupling reaction always requires harsh catalytic reaction conditions and focuses on pure CO2 gas. Herein, three nickel-cluster metal-organic frameworks (MOFs) with different functional groups on the bridging-ligands have been synthesized and characterized structurally, presenting unique cages and channels architectural features. Catalytic investigations demonstrated that the amino-functionalized MOFs as a catalyst {[H2N(CH3)2]2[Ni3(µ3-O)(XN)(BDC-NH2)3∙7DMF}n (Ni3-NH2, XN = 6′′-(pyridin4-yl)-4,2′′:4′′,4′′′-terpyridine, H2BDC-NH2 = 2-aminoterephthalic acid) owns higher catalytic activity (96 %) than the other two in the CO2 transformation reaction with aziridine into oxazolidinones under 0.5 MPa within 4 h. Moreover, Ni3-NH2 can be reused at least ten times without significant catalytic activity loss under mild condition. Importantly, Ni3-NH2 catalyst still can be applicable to the simulating flue gas with 15 % CO2 as carbon source. The mechanism has been further revealed by NMR, FT-IR and DFT calculations, in which the Ni-site and the amino group can synergistically activate the substrate and CO2 molecule. This work has enriched the species of cluster-based MOFs and investigated the influence of characteristic functional groups on the catalytic activity deeply.

Tuning the Photophysical and Photochemical Properties of Rare-Earth Cluster-Based Metal–Organic Frameworks

Tuning the Photophysical and Photochemical Properties of Rare-Earth Cluster-Based Metal–Organic Frameworks

Synthesis, Characterization and Photophysical Properties of a New Family of Rare-Earth Cluster-Based Metal-Organic Frameworks.

In this work, nine new rare-earth metal-organic frameworks (RE-MOFs, where RE=Lu(III), Yb(III), Tm(III), Er(III), Ho(III), Dy(III), Tb(III), Gd(III), and Eu(III)) isostructural to Zr-MOF-808 are synthesized, characterized, and studied regarding their photophysical properties. Materials with high crystallinity and surface area are obtained from a reproducible synthetic procedure that involves the use of two fluorinated modulators. At the same time, these new RE-MOFs display tunable photoluminescent properties due to efficient linker-to-metal energy transfer promoted by the antenna effect, resulting in a series of RE-MOFs displaying lanthanoid-based emissions spanning the visible and near-infrared regions of the electromagnetic spectrum.

Robust {Pb10}-Cluster-Based Metal-Organic Framework for Capturing and Converting CO2 into Cyclic Carbonates under Mild Conditions.

Developing a highly active catalyst that can efficiently capture and convert carbon dioxide (CO2) into high-value-added energy materials remains a severe challenge, which inspires us to explore effective metal-organic frameworks (MOFs) with high chemical stability and high-density active sites. Herein, we report a robust 3D lead(II)-organic framework of {(Me2NH2)2[Pb5(PTTPA)2(H2O)3]·2DMF·3H2O}n (NUC-111) with unreported [Pb10(COO)22(H2O)6] clusters (abbreviated as {Pb10}) as nodes (H6PTTPA = 4,4',4″-(pyridine-2,4,6-triyl)triisophthalic acid). After thermal activation, NUC-111a is functionalized by the multifarious symbiotic acid-base active sites of open Pb2+ sites and uncoordinated pyridine groups on the inner surface of the void volume. Gas adsorption tests confirm that NUC-111a displays a higher separation performance for mixed gases of f CO2 and CH4 with the selectivity of CO2/CH4 at 273 K and 101 kPa being 31 (1:99, v/v), 23 (15:85, v/v), and 8 (50:50, v/v), respectively. When the temperature rises to 298 K, the selectivity of CO2/CH4 at 101 kPa is 26 (1:99, v/v), 22 (15:85, v/v), and 11 (50:50, v/v). Moreover, activated NUC-111a exhibited excellent catalytic performance, stability, and recyclability for the cycloaddition of CO2 with epoxides under mild conditions. Hence, this work provides valuable insight into designing MOFs with multifunctionality for CO2 capture, separation, and conversion.

Heterometallic [FexM3–x(μ3-O)] cluster-based metal–organic frameworks for magnetic properties

In the paper, we construct a class of heterometallic [FexM3–x(μ3-O)] cluster-based MOFs (PCN-250 (Fe2M), M = Fe3, Fe2Co, Fe2Ni and Fe2Co0.5Ni0.5) through modularization by solvothermal method. The structures of PCN-250 (Fe2M) contain heterometallic [FexM3–x(μ3-O)] cluster by carboxylate bridges and further connected with 3,3 ’, 5,5′ − azobenzene tetracarboxylic acid to form 3D networks. Moreover, magnetic investigations indicate that PCN-250 (Fe3) and PCN-250 (Fe2Co) possess antiferromagnetic behavior, while PCN-250 (Fe2Ni) and PCN-250 (Fe2Co0.5Ni0.5) display canted antiferromagnetic behavior with weak ferromagnetism.

Cluster-Cluster Co-Nucleation Induced Defective Polyoxometalate-Based Metal-Organic Frameworks for Efficient Tandem Catalysis.

The construction of defective sites is one of the effective strategies to create high-activity Metal-Organic frameworks (MOFs) catalysts. However, traditional synthesis methods usually suffer from cumbersome synthesis steps and disordered defect structures. Herein, a cluster-cluster co-nucleation (CCCN) strategy is presented that involves the in situ introduction of size-matched functional polyoxometalates (H6P2W18O62, {P2W18}) to intervene the nucleation process of cluster-based MOFs (UiO-66), achieving one-step inducement of exposed defective sites without redundant post-processing. POM-induced UiO-66 ({P2W18}-0.1@UiO-66) exhibits a classical reo topology for well-defined cluster defects. Moreover, the defective sites and the interaction between POM and skeletal cluster nodes are directly observed by Integrated Differential Phase Contrast in Scanning Transmission Electron Microscopy (iDPC-STEM). Owing to the molecular-level proximity between defective sites and POM in the same nano-reaction space, {P2W18}-0.1@UiO-66 exhibits efficient tandem catalysis in the preparation of γ-valerolactone (γ-GVL) from laevulinic acid (LA) by the combination of Lewis and Brønsted acids with 11 times higher performance than defective UiO-66 formed by conventional coordination modulation strategy. The CCCN strategy is applicable to different POM and has the potential to be extended to other cluster-based MOFs, which will pave a new way for the construction of functional MOFs with multi-centered synergistic catalysis.

Sub-Nanometer Mono-Layered Metal-Organic Frameworks Nanosheets for Simulated Flue Gas Photoreduction.

The dilemma between the thickness and accessible active site triggers the design of porous crystalline materials with mono-layered structure for advanced photo-catalysis applications. Here, a kind of sub-nanometer mono-layered nanosheets (Co-MOF MNSs) through the exfoliation of specifically designed Co3 cluster-based metal-organic frameworks (MOFs) is reported. The sub-nanometer thickness and inherent light-sensitivity endow Co-MOF MNSs with fully exposed Janus Co3 sites that can selectively photo-reduce CO2 into formic acid under simulated flue gas. Notably, the production efficiency of formic acid by Co-MOF MNSs (0.85mmolg-1h-1) is ≈13 times higher than that of the bulk counterpart (0.065mmolg-1h-1) under a simulated flue gas atmosphere, which is the highest in reported works up to date. Theoretical calculations prove that the exposed Janus Co3 sites with simultaneously available sites possess higher activity when compared with single Co site, validating the importance of mono-layered nanosheet morphology. These results may facilitate the development of functional nanosheet materials for CO2 photo-reduction in potential flue gas treatment.

Rare [Cu4I2]2+ cationic cluster-based metal-organic framework and hierarchical porous composites design for effective detection and removal of roxarsone and antibiotics

Fluorescence quenching induced by photoinduced electron transfer (PET) stands as an effective strategy for identifying water pollutants. Herein, a novel (4, 8)-connected three-dimensional framework Cu(I)-MOF ([Cu2I(tpt)]n) with unique 8-connected [Cu4I2]2+ cationic clusters is designed by employing the nitrogen-rich ligand (Htpt = 5-[4(1H-1,2,4-triazol-1-yl)]phenyl-2H-tetrazole). Water-stabilized Cu(I)-MOF exhibits outstanding fluorescence properties, facilitating its application in detecting organic pollutants in water. Benefiting from the fact that the Cu(I)-MOF possesses a higher lowest unoccupied molecular orbitals (LUMO) energy level than that of the analyte, the rapid d-PET can occur, entitling Cu(I)-MOF to a sensitive fluorescence quenching response to roxarsone (ROX), nitrofurazone (NFZ) and nitrofurantoin (NFT) (with detection limits as low as 0.13 µM, 0.15 µM, and 0.13 µM, respectively). The nitrogen-containing sites of melamine foam (MF) are utilized to facilitate the anchoring and growth of Cu-MOF crystals, which enables the preparation of hierarchical microporous − macroporous Cu(I)-MOF/MF composites. The ordered porous structure of Cu(I)-MOF/MF provides cavities and open sites for the efficient removal of ROX (qmax = 210.6 mg∙g−1), NFZ (qmax = 111.5 mg∙g−1) and NFT (qmax = 238.9 mg∙g−1) from water. This characteristic endows the Cu(I)-MOF/MF with rapid and recyclable adsorption capacity. Therefore, this work provides valuable insights to address the problem of detection and removal of pollutants in the aquatic environment.

Dual-Color Visual Ratiometric Fluorescence Sensing for H2O and D2O Mixtures Using a Hexanuclear Ln(III) Cluster-Based Metal-Organic Framework.

High-purity heavy water (D2O) is a strategic material owing to its important application in the fields of nuclear energy and scientific research. D2O always tends to get contaminated by H2O owing to its strong hygroscopicity. Herein, a bimetallic hexanuclear Ln(III) cluster-based metal-organic framework (Eu0.5Tb0.5-TZB-MOF) has been synthesized for fluorescence sensing of the D2O-H2O binary mixtures. Eu0.5Tb0.5-TZB-MOF can be used to immediately differentiate D2O or H2O via fluorescent color responses that are obvious to the naked eye and allow for quantitative ratiometric analysis using simple spectrophotometry. Fluorescence titration experiments demonstrate that both trace H2O in D2O and trace D2O in H2O can be quantitatively detected. Mechanistic studies demonstrate that the weaker vibrational quenching of the O-D oscillator compared to the O-H oscillator, in addition to the terbium-to-europium energy transfer, triggered the fluorescence signal response.

Room-temperature ferrimagnetism and size-modulated electronic structures in two-dimensional cluster-based metal-organic frameworks

Room-temperature ferrimagnetism and size-modulated electronic structures in two-dimensional cluster-based metal-organic frameworks

Rare-earth acetates as alternative precursors for rare-earth cluster-based metal-organic frameworks.

RE-UiO-66 analogues are synthesized using RE acetates as precursors for the first time. These MOFs are fully characterized and the influence of the precursor on the materials obtained is studied. Additionally, the influence of water on the yield of the syntheses and the quality of the materials is explored.

High-efficient green catalytic conversion for waste CS2 by non-noble metal cage-based MOFs: An access to high-valued thiazolidine-2-thione

Green and effective disposal of Carbon disulfide (CS2) waste into high-valued chemicals under mild conditions is meaningful and challenging. Herein, a novel 3D cluster-based metal-organic framework (MOF) {(Me2NH2)2[Co3(µ3-O)(XN)(BDC)3]∙4DMF∙5MeOH}n (compound 1)...

Mechanism of Benzene Hydroxylation on Tri-Iron Oxo-Centered Cluster-Based Metal–Organic Frameworks

Mechanism of Benzene Hydroxylation on Tri-Iron Oxo-Centered Cluster-Based Metal–Organic Frameworks

Simultaneous Capture of CO2 Boosting Its Electroreduction in the Micropores of a Metal-organic Framework.

Integration of CO2 capture capability from flue gas and electrochemical CO2 reduction reaction (eCO2RR) active sites into a catalyst is a promising cost-effective strategy for carbon neutrality, but is of great difficulty. Herein, combining the mixed gas breakthrough experiments and eCO2RR tests, we showed that a Ag12 cluster-based metal-organic framework (1-NH2, aka Ag12bpy-NH2), simultaneously possessing CO2 capture sites as "CO2 relays" and eCO2RR active sites, can not only utilize its micropores to efficiently capture CO2 from simulated flue gas (CO2:N2 = 15:85, at 298 K), but also catalyze eCO2RR of the adsorbed CO2 into CO with an ultra-high CO2 conversion of 60%. More importantly, its eCO2RR performance (a Faradaic efficiency (CO) of 96% with a commercial current density of 120 mA cm-2 at a very low cell voltage of -2.3 V for 300 hours and the full-cell energy conversion efficiency of 56%) under simulated flue gas atmosphere is close to that under 100% CO2 atmosphere, and higher than those of all reported catalysts at higher potential under 100% CO2 atmosphere. This work bridges the gap between CO2 enrichment/capture and eCO2RR.

Development of a Mixed Multinuclear Cluster Strategy in Metal-Organic Frameworks for Methane Purification and Storage.

Metal-organic frameworks (MOFs) have attracted extensive attention in methane (CH4) purification and storage. Specially, multinuclear cluster-based MOFs usually have prominent performance because of large cluster size and abundant open metal sites. However, compared to diverse combinations of organic linkers, one MOF with two or more multinuclear clusters is difficult to achieve. In this paper, we demonstrate a mixed multinuclear cluster strategy, which successfully led to three new heterometallic MOFs (SNNU-328-330) with the same common H3TATB [2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine] tritopic linker and six types of multinuclear clusters ([YCd(COO)4(μ2-H2O)], [YCd2(COO)8], [In3(COO)6(μ3-OH)], [In3Eu2(COO)9(μ3-OH)3(μ4-O)], [Y9(COO)12(μ3-OH)14] and [Y2Cd8(COO)16(μ2-H2O)4(μ3-OH)8]). Three MOF adsorbents all show great potentials to remove the impurities (CO2 and C2-hydrocarbons) in natural gas and show prominent high-pressure methane storage capacity. Among them, the ideal adsorbed solution theory separation ratios of equimolar C2H2/CH4, C2H4/CH4, C2H6/CH4, and CO2/CH4 at 298 K for SNNU-328 reach to 29.7-16.0, 19.1-8.2, 33.2-10.3, and 74.3-8.5, which have surpassed many famous MOF adsorbents. Dynamic breakthrough experiments conducted at 273 and 298 K showed that SNNU-330 can separate CH4 from C2H2/CH4, C2H4/CH4, C2H6/CH4, and CO2/CH4 mixtures with the breakthrough interval times of about 48.2, 17.9, 37.2, and 17.1 min g-1 (273 K, 1 bar, v/v = 50/50, 2 mL min-1), respectively. Remarkably, SNNU-329 exhibits extremely high methane storage performance at 298 K with the total uptake and working capacity of 192 cm3 cm-3 (95 bar) and 171 cm3 cm-3 (65 bar) due to the synergistic effects of high surface area, suitable pore sizes, and multiple open metal sites.

A [Cu2I2] cluster-based lanthanide metal–organic framework (MOF) catalyst for the highly efficient conversion of CO2 with propargylic alcohols and aziridines

A new metal–organic framework (MOF) with the formula [Eu2Cu2I2(IN)6(DMF)4]·4DMF (1) (HIN = isonicotinic acid, DMF = N,N-dimethylformamide) based on lanthanide ions and copper iodide clusters (Cu2I2) have been successfully constructed and characterized. Structural analysis indicates that the [Cu2I2] cluster-based lanthanide MOF 1 displays a two-dimensional plane with sql topology. Catalytic study indicates that MOF 1 can efficiently catalyze the propargylic alcohols or aziridines with CO2 under mild conditions. What's more, 1 as a heterogeneous catalyst can be recycled at least five times without obvious loss of catalytic performance. To our best knowledge, it is a rare example of a [Cu2I2] cluster-based lanthanide MOF catalyst that can catalyze both aziridines and propargylic amines with CO2 simultaneously under mild conditions.

High Performance Dynamic X-ray Flexible Imaging Realized Using a Copper Iodide Cluster-Based MOF Microcrystal Scintillator.

X-ray imaging technology has achieved important applications in many fields and has attracted extensive attentions. Dynamic X-ray flexible imaging for the real-time observation of the internal structure of complex materials is the most challenging type of X-ray imaging technology, which requires high-performance X-ray scintillators with high X-ray excited luminescence (XEL) efficiency as well as excellent processibility and stability. Here, a macrocyclic bridging ligand with aggregation-induced emission (AIE) feature was introduced for constructing a copper iodide cluster-based metal-organic framework (MOF) scintillator. This strategy endows the scintillator with high XEL efficiency and excellent chemical stability. Moreover, a regular rod-like microcrystal was prepared through the addition of polyvinyl pyrrolidone during the in situ synthesis process, which further enhanced the XEL and processibility of the scintillator. The microcrystal was used for the preparation of a scintillator screen with excellent flexibility and stability, which can be used for high-performance X-ray imaging in extremely humid environments. Furthermore, dynamic X-ray flexible imaging was realized for the first time. The internal structure of flexible objects was observed in real time with an ultrahigh resolution of 20 LP mm-1 .