3D Metal-organic Framework Research Articles

Tuning the Stacking Modes of Ultrathin Two-Dimensional Metal-Organic Framework Nanosheet Membranes for Highly Efficient Hydrogen Separation.

Two-dimensional (2D) metal-organic framework (MOF) membranes are considered potential gas separation membranes of the next generation due to their structural diversity and geometrical functionality. However, achieving a rational structure design for a 2D MOF membrane and understanding the impact of MOF nanosheet stacking modes on membrane separation performance remain challenging tasks. Here, we report a novel kind of 2D MOF membrane based on [Cu2 Br(IN)2 ]n (IN=isonicotinato) nanosheets and propose that synergetic stacking modes of nanosheets have a significant influence on gas separation performance. The stacking of the 2D MOF nanosheets is controlled by solvent droplet dynamic behaviors at different temperatures of drop coating. Our 2D MOF nanosheet membranes exhibit high gas separation performances for H2 /CH4 (selectivity >290 with H2 permeance >520 GPU) and H2 /CO2 (selectivity >190 with H2 permeance >590 GPU) surpassing the Robeson upper bounds, paving a potential way for eco-friendly H2 separation.

Tuning the Stacking Modes of Ultrathin Two‐Dimensional Metal–Organic Framework Nanosheet Membranes for Highly Efficient Hydrogen Separation

AbstractTwo‐dimensional (2D) metal–organic framework (MOF) membranes are considered potential gas separation membranes of the next generation due to their structural diversity and geometrical functionality. However, achieving a rational structure design for a 2D MOF membrane and understanding the impact of MOF nanosheet stacking modes on membrane separation performance remain challenging tasks. Here, we report a novel kind of 2D MOF membrane based on [Cu2Br(IN)2]n (IN=isonicotinato) nanosheets and propose that synergetic stacking modes of nanosheets have a significant influence on gas separation performance. The stacking of the 2D MOF nanosheets is controlled by solvent droplet dynamic behaviors at different temperatures of drop coating. Our 2D MOF nanosheet membranes exhibit high gas separation performances for H2/CH4 (selectivity >290 with H2 permeance >520 GPU) and H2/CO2 (selectivity >190 with H2 permeance >590 GPU) surpassing the Robeson upper bounds, paving a potential way for eco‐friendly H2 separation.

"Photochemical Surgery" of 1D Metal-Organic Frameworks with a Site-Selective Solubilization/Crystallization Strategy.

One-dimensional (1D) hybrid MOFs are attractive if they consist of different MOF blocks with interconnected channels. However, the precision synthesis of such 1D multiblock MOFs with the desired block lengths and sequences remains a formidable challenge. Herein we propose the "photochemical surgery" method, which combines top-down and bottom-up approaches to enable the site-selective solubilization (removal)/crystallization (reconstruction) of 1D MOFs. We employed photoreactive MOFs, which were prepared by complexing either Cd2+ or Zn2+ with a mixture containing a photochromic bispyridyl ligand (PyDTEopen or PyDTZEopen) and an isophthalate (5-nitroisophthalate (nip2-) or 5-bromoisophthalate (bip2-)). These MOFs were obtained as high-aspect-ratio, needlelike, colorless crystals that bore 1D channels oriented parallel to the long needle axis. When photoreactive DTECdMOFNO2 ([Cd(nip)(PyDTEopen)(H2O)]n), for example, was immobilized at both ends with a metal alloy on a glass substrate and exposed to UV light through a photomask for 60 min in N,N-dimethylformamide/methanol (DMF/MeOH), the unmasked part was removed via solubilization to produce a 50 μm gap. The resulting specimen was immersed for 24 h at 25 °C in DMF/MeOH containing the necessary components for the construction of DTZECdMOFNO2 ([Cd(nip)(PyDTZEopen)(H2O)]n). Eventually, the gap was filled with DTZECdMOFNO2 to produce a triblock hybrid MOF (DTECdMOFNO2-DTZECdMOFNO2-DTECdMOFNO2). The result of a guest diffusion experiment confirmed that the newly formed DTZECdMOFNO2 block shared its 1D channels with the host DTECdMOFNO2 blocks. "Photochemical surgery" can be applied to synthesize 1D hybrid MOFs bearing unconventional sequences and morphologies, e.g., honeycomb- and inverted-honeycomb-patterned hybrids.

Exfoliation of 2D Metal-Organic Frameworks: toward Advanced Scalable Materials for Optical Sensing.

Two-dimensional metal-organic frameworks (MOFs) occupy a special place among the large family of functional 2D materials. Even at a monolayer level, 2D MOFs exhibit unique sensing, separation, catalytic, electronic, and conductive properties due to the combination of porosity and organo-inorganic nature. However, lab-to-fab transfer for 2D MOF layers faces the challenge of their scalability, limited by weak interactions between the organic and inorganic building blocks. Here, comparing three top-down approaches to fabricate 2D MOF layers (sonication, freeze-thaw, and mechanical exfoliation), The technological criteria have established for creation of the layers of the thickness up to 1nm with a record aspect ratio up to 2*10^4:1. The freezing-thaw and mechanical exfoliation are the most optimal approaches; wherein the rate and manufacturability of the mechanical exfoliation rivaling the greatest scalability of 2D MOF layers obtained by freezing-thaw (21300:1vs 1330:1 aspect ratio), leaving the sonication approach behind (with a record 900:1 aspect ratio) have discovered. The high quality 2D MOF layers with a record aspect ratio demonstrate unique optical sensitivity to solvents of a varied polarity, which opens the way to fabricate scalable and freestanding 2D MOF-based atomically thin chemo-optical sensors by industry-oriented approach.

Ultrathin 2D Pd/Cu Single-Atom MOF Nanozyme to Synergistically Overcome Chemoresistance for Multienzyme Catalytic Cancer Therapy.

Single-atom nanozymes (SAzymes) have obtained increasing interest to mimic natural enzymes for efficient cancer therapy, while challenged by chemoresistance from cellular redox homeostasis and the interface of reductive species in tumor microenvironment (TME). Herein, a dual single-atomic ultrathin 2D metal organic framework (MOF) nanosheet of multienzyme (Pd/Cu SAzyme@Dzy) is prepared to synergistically overcome chemoresistance for multienzyme enhanced cancer catalytic therapy. The Pd SAzyme exhibits peroxidase (POD)-like catalytic activity for overcoming chemoresistance via disturbing cellular redox balance. This is further enhanced by cascade generation of more ∙OH via Cu+ -catalyzed POD-like reactions, initiated by in situ-reduction of Cu2+ into Cu+ upon GSH depletion. This process can also avoid the consumption of ∙OH by endogenous reductive GSH in TME, ensuring the adequate amount of ∙OH for highly efficient therapy. Besides, the DNAzyme is also delivered for gene therapy of silencing cancer-cell-targeting VEGFR2 protein to further enhance the therapy. Based on both experiments and theoretical calculations, the synergetic multienzyme-based cancer therapy is examined and the enhancement by the cascade tumor antichemoresistance is revealed.

Haldane topological spin-1 chains in a planar metal-organic framework

Haldane topological materials contain unique antiferromagnetic chains with symmetry-protected energy gaps. Such materials have potential applications in spintronics and future quantum computers. Haldane topological solids typically consist of spin-1 chains embedded in extended three-dimensional (3D) crystal structures. Here, we demonstrate that [Ni(μ−4,4′-bipyridine)(μ-oxalate)]n (NiBO) instead adopts a two-dimensional (2D) metal-organic framework (MOF) structure of Ni2+ spin-1 chains weakly linked by 4,4′-bipyridine. NiBO exhibits Haldane topological properties with a gap between the singlet ground state and the triplet excited state. The latter is split by weak axial and rhombic anisotropies. Several experimental probes, including single-crystal X-ray diffraction, variable-temperature powder neutron diffraction (VT-PND), VT inelastic neutron scattering (VT-INS), DC susceptibility and specific heat measurements, high-field electron spin resonance, and unbiased quantum Monte Carlo simulations, provide a detailed, comprehensive characterization of NiBO. Vibrational (also known as phonon) properties of NiBO have been probed by INS and density-functional theory (DFT) calculations, indicating the absence of phonons near magnetic excitations in NiBO, suppressing spin-phonon coupling. The work here demonstrates that NiBO is indeed a rare 2D-MOF Haldane topological material.

(First Place Poster Award) Probing Charge Transport Mechanisms in 2D Metal Organic Frameworks

Metal Organic Frameworks (MOFs) are a class of highly porous crystalline materials that are constructed from zero- or one-dimensional inorganic chains in combination with multitopic organic ligands.1 They have received great attention recently due to their large surface area, tunable porosity, and easy preparation, which lead to their versatile applications including gas storage2 and separation3, sensing4, catalysis5 and drug delivery6. The versatility of MOFs is further entrenched in the vast available design space offered by the enormous number of metal-linker combinations7, 8. However, majority of MOFs are insulators with very few of them showing appreciable electrical conductivity. The insulating nature of MOFs can be traced back to the starting materials used in constructing these hybrid materials9. Although conductive MOFs have been reported, very little information about the mechanism of charge transport is available.10-12 There are mainly two types of charge transport mechanism reported in such materials, hopping and band transport.13 Hopping mechanism is dominated by movement of charges from donor to acceptor moieties due to charge localization which exists at specific sites within the MOF.13 Band transport relies on delocalization of carriers throughout the valence and conduction bands.14 These mechanisms require low energy pathways for charge transport which are not present in MOFs. Recently, researchers have focused on two synthetic approaches from a chemical perspective to achieve such low energy pathways; through bond approach and through space approach.13 Ideally, both pathways can either lead to band or hopping transport. The through space mechanism utilizes non-covalent interactions like π-π stacking between organic linkers, which creates an extended pathway for charge delocalization usually pronounced in 2D MOFs.15, 16 Recent studies which have successfully quantified and identified charge carrier types in MOFs17 show that conductivity increases mainly with chemical oxidation signifying hole formation18, but mobility and directional charge transfer is still limited by geometry.19 Although the field of electrically conductive MOFs has experienced tremendous expansion in the last decade and yielded a variety of MOFs with high mobility and conductivity, majority of these works focus on material design principle and conductivity measurement, leaving the fundamental understanding of CT mechanism underexplored; yet the latter is essential for the further development of this class of materials to be exploited in optoelectronics, solar cells, and photocatalysis. I will present my progress in exploring CT mechanisms in 2D MOFs using advanced spectroscopic techniques.ReferencesC. Janiak and J. K. Vieth, New J. Chem., 2010, 34, 2366-2388.M. Latroche, S. Surble, C. Serre, C. Mellot-Draznieks, P. L. Llewellyn, J. H. Lee, J. S. Chang, S. H. Jhung and G. Ferey, Angewandte Chemie-International Edition, 2006, 45, 8227-8231.Z. J. Zhang, Y. G. Zhao, Q. H. Gong, Z. Li and J. Li, Chem. Commun., 2013, 49, 653-661.E. A. Dolgopolova, A. M. Rice, C. R. Martin and N. B. Shustova, Chem. Soc. Rev., 2018, 47, 4710-4728.Y. X. Zhou, W. H. Hu, S. Z. Yang, Y. B. Zhang, J. Nyakuchena, K. Duisenova, S. Lee, D. H. Fan and J. Huang, Journal of Physical Chemistry C, 2020, 124, 1405-1412.I. A. Lazaro and R. S. Forgan, Coord. Chem. Rev., 2019, 380, 230-259.C. Muschielok and H. Oberhofer, J. Chem. Phys., 2019, 151.L. Sun, M. G. Campbell and M. Dinca, Angewandte Chemie-International Edition, 2016, 55, 3566-3579.P. F. Li and B. Wang, Isr. J. Chem., 2018, 58, 1010-1018.K. W. Nam, S. S. Park, R. dos Reis, V. P. Dravid, H. Kim, C. A. Mirkin and J. F. Stoddart, Nature Communications, 2019, 10, 10.T. Chen, J.-H. Dou, L. Yang, C. Sun, N. J. Libretto, G. Skorupskii, J. T. Miller and M. Dincă, J. Am. Chem. Soc., 2020, 142, 12367-12373.S. S. Park, E. R. Hontz, L. Sun, C. H. Hendon, A. Walsh, T. Van Voorhis and M. Dincă, J. Am. Chem. Soc., 2015, 137, 1774-1777.M. Ko, L. Mendecki and K. A. Mirica, Chem. Commun., 2018, 54, 7873-7891.R. Dong, P. Han, H. Arora, M. Ballabio, M. Karakus, Z. Zhang, C. Shekhar, P. Adler, P. St Petkov, A. Erbe, S. C. B. Mannsfeld, C. Felser, T. Heine, M. Bonn, X. L. Feng and E. Canovas, Nature Materials, 2018, 17, 1027-+.L. Y. Qu, H. Iguchi, S. Takaishi, F. Habib, C. F. Leong, D. M. D'Alessandro, T. Yoshida, H. Abe, E. Nishibori and M. Yamashita, J. Am. Chem. Soc., 2019, 141, 6802-6806.L. S. Xie, E. V. Alexandrov, G. Skorupskii, D. M. Proserpio and M. Dinca, Chemical Science, 2019, 10, 8558-8565.A.C. Hinckley, J. Park, J. Gomes, E. Carlson and Z. Bao, J. Am. Chem. Soc., 2020, 142, 11123-11130. S.

(Invited) Record-High Charge Carrier Mobilities in 2D Covalent- and Metal- Organic Frameworks

Organic based 2D layered materials (2DLMs) including 2D covalent and metal organic frameworks (COFs and MOFs) are promising candidates for traditional applications in gas storage and separation as well as catalysis. This is due to the long-range crystalline order that can be achieved in them as well as their tunable porosity and chemistry. Synthetic chemistry efforts aiming an enhanced coupling between their building block constituents have recently led to the design of (semi-)conducting MOFs and COFs displaying high conductivities and record charge carrier mobilities. These achievements have opened the path for their application in opto-electronics. Yet, despite being a critical aspect for the development of 2DLM based electronics, understanding the true nature of charge transport in these novel materials by stabilising reliable structure-property-function relations is largely unexplored.Here I will present time-resolved high-frequency (terahertz) conductivity studies of state-of-the-art organic based 2DLMs materials revealing semiconducting behaviour and record charge carrier mobilities. First, I will present a detailed characterization for the electronic properties of Zn– and Cu–phthalocyanine-based pyrazine-linked 2D COFs [1,2]. These 2D COFs, synthesized by condensation of metal–phthalocyanine (M = Zn and Cu) and pyrene derivatives, are obtained as polycrystalline-layered semiconductors displaying p-type doping and a band gap of ∼1.2 eV. Hall effect measurements (dc limit) and terahertz (THz) spectroscopy (ac limit) in combination with density functional theory (DFT) calculations demonstrate that varying metal center from Cu to Zn in the phthalocyanine moiety has a negligible effect in the conductivity (∼5 × 10–7 S/cm), charge carrier density (∼1012 cm–3), charge carrier scattering rate (∼3 × 1013 s–1), and effective mass (∼2.3m0) of majority carriers (holes). However, both samples reveal slightly different mobilities that can be attributed to charge carrier localization at crystalline grain boundaries. Furthermore we analyse the effect of iodine doping on the Zn based 2D COFs. The resultant 2D c-COF ZnPc-pz-I2 maintains its structural integrity and displays enhanced conductivity by 3 orders of magnitude, as a result of improved charge carrier concentrations. Hall effect reveal a charge carrier mobility reaching ∼22 cm2/Vs for ZnPc-pz-I2, which represent a record value for 2D c-COFs. An improved mobility upon doping can be traced to an increase in scattering time for free charge carriers, indicating that scattering mechanisms limiting the mobility are mitigated by doping.In the second part of my talk, I present the results concerning a Fe3(THT)2 (THT=2,3,6,7,10,11-hexathioltriphenylene) 2D MOFs [3]. The π-d conjugated samples, synthesized through interfacial method at room temperature, are obtained as a large-area, free-standing films with tunable geometry (size and thickness). The Fe3(THT)2 films are porous (specific surface area of 526±5 m2/g) and semiconducting (with a ~250 meV direct bandgap), and remarkably display band-like charge transport. This finding is directly demonstrated from the Drude-type high-frequency (terahertz) photo-conductivity response obtained in the samples; revealing free-moving, delocalized charge carriers displaying ~220 cm2/Vs mobilities at room temperature; a record charge carrier mobility for MOFs. The temperature dependence of the mobility reveals that the main scattering mechanism limiting the mobility and hence band-like charge transport in this material is related to impurity scattering, so that material improvements may further increase the mobility.The demonstration of band-like charge transport and record-high mobilities in semiconducting 2D COFs and MOFs reveal the potential of (porous) electrically conductive 2DLMs to be employed as active materials in opto-electronics devices.

Ultrafine Pt NanoparticlesAnchored on 2D Metal-Organic Frameworks as Multifunctional Electrocatalysts for Water Electrolysis and Zinc-Air Batteries.

Multifunctional electrocatalysts are crucial to cost-effective electrochemical energy conversion and storage systems requiring mutual enhancement of disparate reactions. Embedding noble metal nanoparticles in 2D metal-organic frameworks (MOFs) are proposed as an effective strategy, however, the hybrids usually suffer from poor electrochemical performance and electrical conductivity in operating conditions. Herein, ultrafine Pt nanoparticles strongly anchored on thiophenedicarboxylate acid based 2D Fe-MOF nanobelt arrays (Pt@Fe-MOF) are fabricated, allowing sufficient exposure of active sites with superior trifunctional electrocatalytic activity for hydrogen evolution, oxygen evolution, and oxygen reduction reactions. The interfacial Fe─O─Pt bonds can induce the charge redistribution of metal centers, leading to the optimization of adsorption energy for reaction intermediates, while the dispersibility of ultrafine Pt nanoparticles contributes to the high mass activity. When Pt@Fe-MOF is used as bifunctional catalysts for water-splitting, a low voltage of 1.65V is required at 100mA cm-2 with long-term stability for 20h at temperatures (65°C) relevant for industrial applications, outperforming commercial benchmarks. Furthermore, liquid Zn-air batteries with Pt@Fe-MOF in cathodes deliver high open-circuit voltages (1.397V) and decent cycling stability, which motivates the fabrication of flexible quasisolid-state rechargeable Zn-air batteries with remarkable performance.

Two-Dimensional Metal–Organic Frameworks and Their Derivative Electrocatalysts for Water Splitting

The escalating urgency to mitigate climate change and enhance energy security has prompted heightened exploration of hydrogen production via electrocatalysis as a viable alternative to conventional fossil fuels. Among the myriad of electrocatalysts under investigation, two-dimensional (2D) metal–organic frameworks (MOFs) stand out as a particularly appealing option. Their unique properties, including a large active specific surface area, distinctive pore structure, ample metal active sites, ultra-thin thickness, superior ion transport efficiency, fast electron transfer rate, and the ability to control the morphological synthesis, endow these frameworks with exceptional versatility and promising potential for electrocatalytic applications. In this review, we delineate the structural features and advantages of 2D MOFs and their derivatives. We proceed to summarize the latest advancements in the synthesis and utilization of these materials for electrocatalytic hydrogen evolution reactions (HER) and oxygen evolution reactions (OER). Finally, we scrutinize the potential and challenges inherent to 2D MOFs and their derivatives in practical applications, underscoring the imperative for continued research in this captivating field of electrocatalysis.

Enhancing Nanofiltration Selectivity of Metal-Organic Framework Membranes via a Confined Interfacial Polymerization Strategy.

Development of well-constructed metal-organic framework (MOF) membranes can bring about breakthroughs in nanofiltration (NF) performance for water treatment applications, while the relatively loose structures and inevitable defects usually cause low rejection capacity of MOF membranes. Herein, a confined interfacial polymerization (CIP) method is showcased to synthesize polyamide (PA)-modified NF membranes with MOF nanosheets as the building blocks, yielding a stepwise transition from two-dimensional (2D) MOF membranes to polyamide NF membranes. The CIP process was regulated by adjusting the loading amount of piperazine (PIP)-grafted MOF nanosheets on substrates and the additional content of free PIP monomers distributed among the nanosheets, followed by the reaction with trimesoyl chloride in the organic phase. The prepared optimal membrane exhibited a high Na2SO4 rejection of 98.4% with a satisfactory water permeance of 37.4 L·m-2·h-1·bar-1, which could be achieved by neither the pristine 2D MOF membranes nor the PA membranes containing the MOF nanosheets as the conventional interlayer. The PA-modified MOF membrane also displayed superior stability and enhanced antifouling ability. This CIP strategy provides a novel avenue to develop efficient MOF-based NF membranes with high ion-sieving separation performance for water treatment.

Construction of Well-Defined Two-Dimensional Architectures of Trimetallic Metal-Organic Frameworks for High-Performance Symmetric Supercapacitors.

The high surface-to-volume ratio and extraordinarily large-surface area of two-dimensional (2D) metal-organic framework (MOF) architectures have drawn particular interest for use in supercapacitors. To achieve an excellent electrode material for supercapacitors, well-defined 2D nanostructures of novel trimetallic MOFs were developed for supercapacitor applications. Multivariate MOFs (terephthalate and trimesate MOF) with distinctive nanobrick and nanoplate-like structures were successfully synthesized using a straightforward one-step reflux condensation method by combining Ni, Co, and Zn metal species in equimolar ratios with two different ligands. Furthermore, the effects of the tricarboxylic and dicarboxylic ligands on cyclic voltammetry, charge-discharge cycling, and electrochemical impedance spectroscopy were studied. The derived terephthalate and trimesate MOFs are supported with stainless-steel mesh and provide a suitable electrolyte environment for rapid faradaic reactions with an elevated specific capacity, excellent rate capability, and exceptional cycling stability. It shows a specific capacitance of 582.8 F g-1, a good energy density of 40.47 W h kg-1, and a power density of 687.5 W kg-1 at 5 mA cm-2 with an excellent cyclic stability of 92.44% for 3000 charge-discharge cycles. A symmetric BDC-MOF//BDC-MOF supercapacitor device shows a specific capacitance of 95.22 F g-1 with low capacitance decay, high energy, and power densities which is used for electronic applications. These brand-new trimetallic MOFs display outstanding electrochemical performance and provide a novel strategy for systematically developing high-efficiency energy storage systems.

Stability and reactivity improved bimetallic 2D metal organic frameworks for electrocatalytic degradation of p-acetaminophenol

The blooming consumption and disposal of p-acetaminophenol (APAP) calls for green technology for pollution control with high efficiency. In this study, series eco-friendly bimetallic 2D Metal-Organic Frameworks (MOFs)—(NixCuy)HITP were prepared as anode materials for APAP electrocatalytic degradation. With the co-existence of bimetallic centers, about 11–18 % enhanced performance was obtained by comparing with Ni3(HITP)2 and Cu3(HITP)2, resulting in 98 % APAP removal in 40 min. For mechanism, both experiment (Ni/Cu modulation and H2SO4 etching) and density functional theory (DFT) results proved the contributions of metal sites for electron transfer acceleration, rather than as direct active sites. The accelerated electron transfer then bloomed the secondary active species generation, including active chlorine, •O2− and 1O2. Meanwhile, the superior stability and reactivity of (NixCuy)HITP encountered attractive pH tolerance and recycle possibility for practical application. The detailed APAP degradation pathways were further provided according to GC-MS results to complete whole process mechanism discussion from “reaction site” to “activated species ’’ to “ pollutant degradation pathways”.

Two 3D Two-Fold Interpenetrated Dia-Like Polyoxometalate-Based Metal-Organic Frameworks: Synthesis and Sulfide Selective Oxidation Activity.

Two new three-dimensional (3D) polyoxometalate-based metal-organic frameworks (POMOFs), [M2(btap)4(H2O)4(HPMo10VI Mo2VO40)] (M = Co (1) and Cd (2); btap = 3, 5-bis(1', 2', 4'-triazol-1'-yl)pyridine), have been synthesized under mild hydrothermal conditions and characterized in detail. Single-crystal X-ray diffraction (SXRD) analysis indicates that 1 and 2 are isostructural. In complexes 1 and 2, the metal ion is coordinated with the ligand to form two different left and right helical one-dimensional chains, which are alternately connected in a twisted form to build a two-fold interpenetrated three-dimensional structure, and the polyoxometalate is encapsulated into in the pores generated by the interpenetrating structure. It is noteworthy that 1 and 2, as recyclable catalysts, possess favorable heterogeneous catalytic activity and excellent sulfoxide selectivity in sulfide oxidation reactions, with H2O2 as an oxidant. By reason of the high dispersion of polyoxometalate with good intrinsic activity in the skeleton structure, the title complex has high activity. In addition, no obvious decrease of sulfoxide yield is observed after at least five cycles. These results indicate the excellent catalytic activity and sustainability of 1 and 2.

Magnetic Real Chern Insulator in 2D Metal-Organic Frameworks.

Real Chern insulators have attracted great interest, but so far, their material realization is limited to nonmagnetic crystals and systems without spin-orbit coupling. Here, we reveal the magnetic real Chern insulator (MRCI) state in a recently synthesized metal-organic framework material Co3(HITP)2. Its ground state with in-plane ferromagnetic ordering hosts a nontrivial real Chern number, enabled by the C2zT symmetry and robustness against spin-orbit coupling. Distinct from previous nonmagnetic examples, the topological corner zero modes of MRCIs are spin-polarized. Furthermore, under small tensile strains, the material undergoes a topological phase transition from the MRCI to a magnetic double-Weyl semimetal phase, via a pseudospin-1 critical state. Similar physics can also be found in closely related materials Mn3(HITP)2 and Fe3(HITP)2, which also exist. Possible experimental detections and implications of an emerging magnetic flat band in the system are discussed.

TiO2 embedded in ultrathin N-doping carbon nanosheets derived from shape-engineered titanium metal-organic frameworks for lithium-ion storage

The utility of TiO2 as an anode for lithium-ion storage is hindered by low conductivity and sluggish ionic diffusion. Here, the 2D N-doped carbon-wrapped TiO2 (TiO2 @NC) composite with a thickness of 5.5 nm derived from the 2D metal-organic framework was designed. This composite consisting of TiO2 nanoparticles embedded in ultrathin N-doping carbon was used to address the rate and cyclability of Li-ion batteries. The 2D nanosheet morphology obtained from Ti8O8(OH)4(BDC-NH2)6（NH2-MIL-125 (Ti)）effectively increases the specific surface area and shortens the electron/ion transport pathway. The chemical bond of Ti-C-O between TiO2 nanocrystals and N-doping carbon further improve conductivity. Due to its unique structure, the produced TiO2 @NC composite shows excellent cyclability with a reversible capacity of 110 mAh g–1 after 2000 cycles at 0.5 A g–1. Furthermore, the 2D TiO2 @NC exhibits outstanding rate performance (71 mAh g–1 at 5 A g–1) compared to bulk TiO2 @NC. This general concept can be extended to the development of metal oxide materials based on insertion mechanisms, such as Nb2O5.

Density functional theory–guided electrochemical determination of nitrite in foods based on 2D metal-organic frameworks

This paper presents results for four types of morphology-controlled two-dimensional cobalt based tetrakis (4-carboxyphenyl) porphyrin metal-organic frameworks (2D Co-TCPP MOFs) with different catalytic properties for nitrite, and an electrochemical sensor was fabricated by the Co-TCPP MOF with superior catalytic properties. The sensor exhibited a high sensitivity of 311.3 μg/g, an extra low detection limit (LOD) of 0.03 μM, and a wide linear range of 0.1–375 μM, which was applied successfully for nitrite detection in water, milk and sausage. Moreover, density functional theory (DFT) calculations were used to establish the sensing method, the adsorption structures of nitrite on the surface of Co-TCPP MOF were built and the electrocatalytic mechanism was confirmed. The results explained why the sensor fabricated by a single Co-TCPP MOF exhibited equal or better performance than reported sensors fabricated by composite materials based on a combination of theory and experiment. This work reported a universal electrochemical sensing method for nitrite detection in food based on a single morphology-controlled 2D TCPP MOF, which provided a new and valuable strategy for establishing an efficient food safety determination method guided by theoretical calculations.

Engineering Functionalized 2D Metal-Organic Frameworks Nanosheets with Fast Li+ Conduction for Advanced Solid LiBatteries.

Solid-state batteries can ensure high energy density and safety in lithium metal batteries, while polymer electrolytes are plagued by slow ion kinetics and low selective transport of Li+ . Metal-organic frameworks (MOFs) are proposed as emerging fillers for solid-state poly(ethylene oxide)(PEO) electrolytes, however, developing functionalized MOFs and understanding their roles on ion transfer has proven challenging. Herein, combining computational and experimental results, the functional group regulation in MOFs can effectively change surficial charge distribution and limit anion movement is revealed, providing a potential solution to these issues. Specifically, functionalized 2D MOF sheets are designed through molecular engineering to construct high-performance composite electrolytes, where the electron-donating effect of substituents in 2D-MOFs effectively limits the movement of ClO4 - and promotes mechanical properties and ion migration numbers (0.36 up to 0.64) of PEO. As a result, Li/Li cells with composite electrolyte exhibit superior cyclability for 1000h at a current density of 0.2mAcm-2 . Meanwhile, the solid LiFePO4 /Li battery delivers highly reversible capacities of 148.8mAh g-1 after 200cycles. These findings highlight a new approach for anion confinement through the use of functional group electronic effects, leading to enhanced ionic conductivity, and a feasible direction for high-performance solid-state batteries.

Rapid Light Response of a Novel Bi‐Based Metal–Organic Framework for Bacterial Wound Infections Treatment

AbstractBismuth metal–organic frameworks (MOFs) as catalysts are scarce. Herein, the first MOF comprising meso‐ tetra(4‐carboxyphenyl) porphine (TCPP) as an organic ligand and Bi ion as a metal node, denoted as Bi‐TCPP, is synthesized by a convenient one‐step hydrothermal method. Compared to other 2D (Cu‐TCPP) or 3D (PCN‐222) MOFs with TCPP as a ligand, Bi‐TCPP has ultrafast singlet oxygen generation ability and a high photothermal conversion efficiency of 49.5% under the irradiation of 660 nm light. This is due to Bi‐TCPP's strong ligand‐to‐metal charge transfer (LMCT) events that form singlet oxygen (1O2). Further, when the electrons and holes above the bandgap relax to the band edge, the excess energy is converted into heat. In vitro and in vivo experiments show excellent antibacterial and repair effects. Hence, the synthesis of Bi‐TCPP provides new ideas for the study of rare bismuth‐based MOFs, and its excellent biocompatibility provides a possibility for further application.

Nanocomposite polymer blend membrane molecularly re-engineered with 2D metal-organic framework nanosheets for efficient membrane CO2 capture

Membrane gas separation technology is an energy-efficient alternative to the traditional industrial processes for CO2 capture towards the mitigation of global warming. To overcome the inherent performance trade-off behavior of polymeric membranes, many nanoarchitectures have been incorporated for developing high-performance mixed matrix membranes. Yet, a successful nanocomposite membrane design remains challenging, especially for CO2 capture, because of polymer-filler incompatibility and interfacial defects. Herein, 2D Cu-TCPP nanosheets were synthesized and incorporated into Pebax/Poly (ethylene glycol) methyl ether acrylate (PEGMEA) blends to design MMMs with exceptional CO2/N2 separation performance. This synergistic polymer blend after crosslinking, offers a highly accommodating and robust matrix environment for the homogenous distribution of nanosheets. Cu-TCPP particles were also produced as 3D nanoflowers to probe their morphological effect on gas transport. The finely dispersed 2D nanosheets expanded the free volume of the resultant nanocomposite membranes, leading to a significantly enhanced CO2 permeability of up to 1183 Barrer which was 93% higher than the neat polymers, while they also increased the transport pathway tortuosity that contributes to a very high CO2/N2 selectivity of 57.6 at a loading of merely 0.1 wt%. Not only do such separation performances surpassed the Robeson upper bound by a large margin and outcompeted many existing advanced MMM designs, but they also remained stable after long-term operations. By carefully elucidating the gas transport tuning effect of 2D metal-organic framework nanosheets in nanocomposite membranes, this work could help broaden their applicability for other environmentally important molecular separations.