Intermolecular And Surface Forces

Materials research has driven the development of modern nano-electronic devices. In particular, research in magnetic thin films has revolutionized the development of spintronic devices1,2 because identifying new magnetic materials is key to better device performance and design. Van der Waals crystals retain their chemical stability and structural integrity down to the monolayer and, being atomically thin, are readily tuned by various kinds of gate modulation3,4. Recent experiments have demonstrated that it is possible to obtain two-dimensional ferromagnetic order in insulating Cr2Ge2Te6 (ref. 5) and CrI3 (ref. 6) at low temperatures. Here we develop a device fabrication technique and isolate monolayers from the layered metallic magnet Fe3GeTe2 to study magnetotransport. We find that the itinerant ferromagnetism persists in Fe3GeTe2 down to the monolayer with an out-of-plane magnetocrystalline anisotropy. The ferromagnetic transition temperature, Tc, is suppressed relative to the bulk Tc of 205 kelvin in pristine Fe3GeTe2 thin flakes. An ionic gate, however, raises Tc to room temperature, much higher than the bulk Tc. The gate-tunable room-temperature ferromagnetism in two-dimensional Fe3GeTe2 opens up opportunities for potential voltage-controlled magnetoelectronics7-11 based on atomically thin van der Waals crystals.

Gate-tunable Room-temperature Ferromagnetism in Two-dimensional Fe 3 GeTe 2

Multifunctional electrocatalysts play an increasingly crucial role in various practical electrochemical energy conversion devices. Especially, on the air cathode of rechargeable zinc–air batteries (ZABs), oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), requiring efficient bifunctional electrocatalysts, are switched during discharging and charging process. Here, supported by the theoretical computations, a facile strategy for the in situ assembly of NiFe-MOFs nanosheets on heteroatoms-doped porous activated carbon spheres is developed. The newly designed electrocatalyst (NP-ACS[email protected]) shows excellent performance toward bifunctional oxygen electrocatalysis. Specifically, a remarkable low value of potential gap (ΔE = 0.61 V), which is the difference between the potential to reach an OER current density of 10 mA cm−2 and ORR half-wave potential, is achieved in 0.1 m KOH. Notably, the aqueous ZAB based on [email protected] shows super cycle stability with small voltage gap of only 0.79 V when cycled for 450 h at 10 mA cm−2. Also, the quasi-solid-state ZAB indicates excellent flexibility and cycling stability. This study presents a facile strategy for the rational integration of different catalytically active components, and can be extended to prepare other strongly competitive multifunctional electrocatalysts. 

Assembling Amorphous Metal–Organic Frameworks onto Heteroatom‐Doped Carbon Spheres for Remarkable Bifunctional Oxygen Electrocatalysis

Abstract 2D metal‐organic frameworks‐based (2D MOF‐related) materials benefit from variable topological structures, plentiful open active sites, and high specific surface areas, demonstrating promising applications in gas storage, adsorption and separation, energy conversion, and other domains. In recent years, researchers have innovatively designed multiple strategies to avoid the adverse effects of conventional methods on the synthesis of high‐quality 2D MOFs. This review focuses on the latest advances in creative synthesis techniques for 2D MOF‐related materials from both the top‐down and bottom‐up perspectives. Subsequently, the strategies are categorized and summarized for synthesizing 2D MOF‐related composites and their derivatives. Finally, the current challenges are highlighted faced by 2D MOF‐related materials and some targeted recommendations are put forward to inspire researchers to investigate more effective synthesis methods. 

Recent Progress in 2D Metal-Organic Framework-Related Materials.

Room temperature ionic liquid (RTIL) electrolytes are excellent candidates for highly stable electrochromic (EC) devices because of their wide electrochemical windows and good environmental stability. However, the small crystal spacings and molecular gaps of conventional EC materials limit the ion-diffusion rate of RTILs’ large cations. The multiple insertions/extractions of large cations can destroy the structure of the conventional EC materials, leading to structural collapse and poor EC performance. Here, we demonstrate that metal-organic frameworks (MOFs) with large intrinsic pores in crystals are promising materials for stable and high-performance RTIL-based EC systems. The MOFs’ large intrinsic hexagonal channels provide suitable ion-transport channels for RTILs, leading to ideal electrochemical stability. We further demonstrate a patterned large-area MOF/RTIL-based EC device, suggesting the promise in future digital displays. 

Ultra-stable ionic-liquid-based electrochromism enabled by metal-organic frameworks

The large-scale preparation of monolayer two-dimensional (2D) material remains a great challenge, which hinders its real-world applications. Herein, we report a novel layered metal–organic framewor...

https://www.chinesechemsoc.org/doi/pdf/10.31635/ccschem.021.202101208

Facile Exfoliation of 2D Crystalline Monolayer Nanosheets from an Amorphous Metal-Organic Framework

Y.C. thanks Prof. Jean-Pierre Sauvage, Enrico Traversa, Jean-Marie Basset, Yi Zhang, Min Liu, Bo Tang, Yu-Bin Dong, Guo-Xia Jin, Tao Yue, Hai Xu for the helpful discussion.

/pdf/2d-crystalline-monolayer-nanosheets-produced-from-1d-31wrgmf0ev.pdf

2D Crystalline Monolayer Nanosheets Produced from 1D-Amorphous Metal-Organic Framework

The invention discloses a novel two-dimensional MOF material and a preparation method of a corresponding single-layer nanosheet. The novel two-dimensional MOF material is the first single-layer two-dimensional material which can be prepared and applied in batches so far. The two-dimensional MOF material is constructed by a building block unit with a three-dimensional structure, the interlayer acting force is very weak, the mechanical strength in the layer is high, and the corresponding single-layer nanosheet material can be prepared on a large scale through simple mechanical stripping. The obtained single-layer nanosheet has the characteristics of high quality, large size and good stability, and is simple to prepare, low in raw material cost and short in time consumption. The single-layernanosheet has the characteristics of large specific surface area, small mass transfer obstruction, full exposure of high-activity sites, excellent performance and the like, and has a good quantum confinement effect, and researches show that the nanosheet material has excellent performances in catalysis, sensing, information, quantum dot matrixes, separation, gas separation and adsorption, ion screening, liquid molecular sieving and the like, and has an important application prospect.

Preparation and application of large-size single-layer two-dimensional MOF nanosheet

The invention discloses a single-layer two-dimensional COFs nanosheet material capable of being prepared in batches and application of the single-layer two-dimensional COFs nanosheet material in membrane separation and catalysis. The COFs material is formed by assembling three-dimensional molecular building blocks with D3h, D4h or Dnh symmetry, the mechanical strength in the layer is high, the interlayer acting force is extremely weak, and the single-layer nanosheet can be prepared through simple mechanical stripping. The two-dimensional COFs nanosheet prepared from the COFs material has the characteristics of high single-layer uniformity, large size, high quality, good stability, large specific surface area, small mass transfer obstruction and the like, shows excellent performance in separation and electrocatalysis of gas and other substances, and has important application prospects.

Two-dimensional COFs nanosheet based on cage-shaped molecular building block and application of two-dimensional COFs nanosheet

Crystal phase is well studied and presents a periodical atom arrangement in three dimensions lattice, but the "amorphous phase" is poorly understood. Here, by starting from cage-like bicyclocalix[2]arene[2]triazines building block, a brand-new 2D MOF is constructed with extremely weak interlaminar interaction existing between two adjacent 2D-crystal layer. Inter-layer slip happens under external disturbance and leads to the loss of periodicity at one dimension in the crystal lattice, resulting in an interim phase between the crystal and amorphous phase - the chaos phase, non-periodical in microscopic scale but orderly in mesoscopic scale. This chaos phase 2D MOF is a disordered self-assembly of black-phosphorus like 3D-layer, which has excellent mechanical-strength and a thickness of 1.15 nm. The bulky 2D-MOF material is readily to be exfoliated into monolayer nanosheets in gram-scale with unprecedented evenness and homogeneity, as well as previously unattained lateral size (>10 um), which present the first mass-producible monolayer 2D material and can form wafer-scale film on substrate.

Chaos Phase Induced Mass-producible Monolayer Two-dimensional Material.

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