Ultrathin 2D Metal Research Articles

Boosting acidic hydrogen peroxide electrosynthesis on 2D metal-organic framework nanosheets based on cobalt porphyrins

The 2-electron electrocatalytic oxygen reduction reaction (2e− ORR) to hydrogen peroxide (H2O2) represents a promising strategy to resolve the high energy consumption and increasing environmental concerns inherent in the traditional anthraquinone process. The acidic 2e− ORR has emerged as an exciting alternative for industrial-level H2O2 production, whereas is hampered by the inferior H2O2 selectivity due to the uncontrollable proton-coupled electron transfer processes in an acidic environment. Herein, an ultrathin 2D metal–organic frameworks (MOFs) nanosheet based on cobalt tetra(4-carboxyphenyl) porphine (Co-TCPP NSs) is designed to promote H2O2 selectivity up to 96.5 %, accompanied with a remarkable H2O2 generation rate of 4677.42 mg·L−1·h−1. Of note, the Co-TCPP NSs also demonstrate its potential for the electro-Fenton process with a cumulative H2O2 concentration of 1.21 wt%, highlighting its practical potential in portable H2O2 generation electrochemical devices for distributed applications. Our findings demonstrated that the efficient H2O2 electrosynthesis could be attributed to the attenuated *OOH adsorption over Co-N4 moiety on the Co-TCPP NSs, which consequently suppresses its further reduction to form H2O. This work highlights the potential of 2D MOF architecture for the 2e− ORR and provides an atomic-level insight into the enhanced H2O2 selectivity.

Pyridine-induced caused structural reconfiguration forming ultrathin 2D metal–organic frameworks for the oxygen evolution reaction

2D Co MOF-Py3 is synthesized by a bottom-up structural reconfiguration strategy by using pyridine for the oxygen evolution reaction.

Ozonolysis–oxidation-driven top-down strategy for the target preparation of ultrathin 2D metal–organic framework monolayers

A novel chemical exfoliation method is developed for the target preparation of 2D MOF monolayers from the 3D pillar-layered MOFs.

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.

Heterogenized molecular Pd(ii) catalyst on ultrathin 2D metal–organic frameworks with nanoflower-like morphology for isonitrile-involved cyclization reaction

An ultrathin 2D MOF based catalyst with fully exposed single-site Pd(ii) active centers shows superior catalytic efficiency for the isonitrile-involved cyclization reaction compared to 3D MOF based Pd(ii) catalyst and homogeneous counterpart.

Constructing ultrathin defective Co3O4/MoS2 nanosheets based 2D/2D heterojunction toward room temperature NH3 detection

Ultrathin 2D/2D face-to-face heterostructures have shown promising applications in gas sensing devices. Synthesis of ultrathin 2D/2D metal oxide/MoS2 based heterostructures, however, remains challenging probably due to the difficulty in preparing ultrathin 2D metal oxides. Here, ultrathin defective Co3O4/MoS2 nanosheets (NSs) with large heterointerfaces and high specific surface area are prepared via in-situ growth of MoS2 on salt-template-synthetic Co3O4 NSs. The as-obtained Co3O4/MoS2 sensor exhibits a high response value of 2.1 toward 5 ppm NH3 at room temperature, outperforming most sensors based on metal oxide/MoS2 reported hitherto. Moreover, the ultrathin defective Co3O4/MoS2 NSs sensor presents excellent selectivity and long-term stability. The excellent gas sensing performances of the Co3O4/MoS2 based sensor are attributed to the presence of rich defects and intimate interfacial electronic interaction, which ensures abundant active adsorption sites and rapid electrons transfer. Our method demonstrates a versatile integration strategy to construct 2D/2D heterostructures for innovative applications including but not limited to the gas sensing fields.

Edge engineering of platinum nanoparticles via porphyrin-based ultrathin 2D metal–organic frameworks for enhanced photocatalytic hydrogen generation

Edge-doping engineering in metal nanoparticles (MNPs) is always hard to achieve due to the high surface energy of the hybrid MNPs, while porphyrin-based ultrathin two-dimensional (2D) metal–organic framework (MOF) is demonstrated the positive role in stabilize this structure. Herein, a bottom-up method was developed to prepare platinum nanoparticles (PtNPs)-decorated 2D MOF nanosheets, where a porphyrin ligand of Pd-metalized tetrakis(4-carboxyphenyl)porphyrin (PdTCPP) was applied to synthesize ultrathin MOF nanosheets as Zr-TCPP(Pd) in high yield. Attributing to the high superficial area of ultrathin Zr-TCPP(Pd) nanosheets, Pt NPs can well anchor uniformly with small nanoparticle size to obtain 2% Pt/Zr-TCPP(Pd) hybrid nanosheets, which showed a higher photocatalytic hydrogen production rate of 3348 μmol g-1h−1. This is attributed to the coordination between Zr4+ and C = O of PVP, which promotes the contact between PtNPs and Zr-TCPP(Pd) nanosheets. As a result, the long-life electrons of PdTCPP photosensitizers are rapidly transferred to the electron capture center PtNPs, and the photoelectron-hole recombination is effectively inhibited. The apparent quantum efficiency of 2% Pt/Zr-TCPP(Pd) reaches up to 1.56% at 420 nm. The density functional theory (DFT) calculations revealed the Pd-doped position in Pt79 nanoparticle is important that the Pt78Pdsurf. model (Pd atom was doped on the surface of Pt nanoparticle) showed the highest activity with abundant exposed active region.

Ultrathin PdAuBiTe Nanosheets as High-Performance Oxygen Reduction Catalysts for a Direct Methanol Fuel Cell Device.

Ultrathin 2D metal nanostructures have sparked a lot of research interest because of their improved electrocatalytic properties for fuel cells. So far, no effective technique for preparing ultrathin 2D Pd-based metal nanostructures with more than three compositions has been published. Herein, a new visible-light-induced template technique for producing PdAuBiTe alloyed 2D ultrathin nanosheets is developed. The mass activity of the PdAuBiTe nanosheets against the oxygen reduction reaction (ORR) is 2.48 A mgPd -1 , which is 27.5/17.7 times that of industrial Pd/C/Pt/C, respectively. After 10000 potential cyclings, there is no decrease in ORR activity. The PdAuBiTe nanosheets exhibit high methanol tolerance and in situ anti-CO poisoning properties. The PdAuBiTe nanosheets, as cathode electrocatalysts in direct methanol fuel cells, can thus give significant improvement in terms of power density and durability. In O2 /air, the power density can be increased to 235.7/173.5mWcm-2 , higher than that reported in previous work, and which is 2.32/3.59 times higher than Pt/C.

Shape-controlled template-driven growth of large CuS hexagonal nanoplates

Ultrathin 2D metal sulphide nanostructures have revealed extraordinary properties, applications and thus, the subject matter of current research. However, synthesis of shape-controlled large-sized (approximately few µms) plates/sheets are not well known, specifically due to the colloidal synthesis process resulting in the distribution of shape/size. Here, we report the template-assisted growth of large-sized CuS nanoplates (~0.5–9 µm) by simple wet chemistry, where the Au microplates serve as a template. The Au microplates act as seed and facilitate the Au-Cu via epitaxial growth of Cu. Later, the Au-Cu acts as the source of Cu and in presence of aqueous S2−, the CuS hexagons form, however, the edge of the hexagons are parallel to the Au seed and thus, hinting to be controlled by the seed. Interestingly, the substrate independent Au-Cu can even provide the platform for the spiral nanoplates, by simply decorating the outer surface of the Cu with pillar-like features.

Metal–Organic Framework Nanosheets for Thin-Film Composite Membranes with Enhanced Permeability and Selectivity

Widespread applications of reverse osmosis (RO)-based processes call for high-performance thin-film composite (TFC) membranes. In this study, a TFC membrane by incorporating an ultrathin 2D metal–o...

Epitaxial growth of metal-semiconductor van der Waals heterostructures NbS2/MoS2 with enhanced performance of transistors and photodetectors

Two-dimensional (2D) heterostructures based on layered transition metal dichalcogenides (TMDs) have attracted increasing attention for the applications of the next-generation high-performance integrated electronics and optoelectronics. Although various TMD heterostructures have been successfully fabricated, epitaxial growth of such atomically thin metal-semiconductor heterostructures with a clean and sharp interface is still challenging. In addition, photodetectors based on such heterostructures have seldom been studied. Here, we report the synthesis of high-quality vertical NbS2/MoS2 metallic-semiconductor heterostructures. By using NbS2 as the contact electrodes, the field-effect mobility and current on-off ratio of MoS2 can be improved at least 6-fold and two orders of magnitude compared with the conventional Ti/Au contact, respectively. By using NbS2 as contact, the photodetector performance of MoS2 is much improved with higher responsivity and less response time. Such facile synthesis of atomically thin metal-semiconductor heterostructures by a simple chemical vapor deposition strategy and its effectiveness as ultrathin 2D metal contact open the door for the future application of electronics and optoelectronics.

Ultrathin 2D Metal\u2013Organic Framework Nanosheets In situ Interpenetrated by Functional CNTs for Hybrid Energy Storage Device

HighlightsThe ultrathin nickel metal–organic framework (MOF) nanosheets in situ interpenetrated by functional carboxylated carbon nanotubes (C-CNTs) were successfully constructed. The incorporated C-CNTs effectively adjust the layer thickness of Ni-MOF nanosheets.The integrated hybrid MOF nanosheets delivered the boosted electrochemical performances and exhibited superior specific capacity of 680 C g−1 at 1 A g−1.

Removal of arsenic(iii) from water by 2D zeolitic imidazolate framework-67 nanosheets

Ultrathin 2D metal–organic framework nanosheets can efficiently and rapidly capture arsenate from water.

Ultrathin 2D metal-organic framework nanosheets prepared via sonication exfoliation of membranes from interfacial growth and exhibition of enhanced catalytic activity by their gold nanocomposites.

Ultrathin two-dimensional (2D) metal–organic framework (MOF) nanosheets were prepared by a facile sonication exfoliation of MOF membranes from interfacial growth. The stacked form of nanosheets constituting the MOF membranes was significantly different to that of its layered MOF counterparts. This led to decreased interaction between nanosheets, so they could exfoliate readily from the MOF membranes. Moreover, Au nanoparticles were introduced to form nanocomposites. Enhanced catalytic activity and long-term stability of these nanocomposites were observed by a model reaction of the reduction of 4-nitrophenol to 4-aminophenol. This preparation method could be extended to other 2D MOF nanosheets and their nanocomposites.

Ultrathin 2D metal–organic framework (nanosheets and nanofilms)-basedxD–2D hybrid nanostructures as biomimetic enzymes and supercapacitors

xD–2D hybrid nanostructures based on ultrathin 2D TCPP MOF exhibit great potential for application in biomimetic catalase and supercapacitors.

Wrinkled Rh2P Nanosheets as Superior pH‐Universal Electrocatalysts for Hydrogen Evolution Catalysis

AbstractSearching for highly efficient and durable electrocatalysts for the hydrogen evolution reaction (HER) that function effectively at all pHs is of great interest to the scientific community, however it is still a grand challenge, because the HER kinetics of Pt in alkaline solutions are approximately two to three orders of magnitude lower than that in acidic solution. Herein, a new class of wrinkled, ultrathin Rh2P nanosheets for enhancing HER catalysis at all pHs is reported. They exhibit a small overpotential of 18.3 mV at 10 mA cm−2, low Tafel slope of 61.5 mV dec−1, and good durability in alkaline media, much better than the commercial Pt/C catalyst. Density functional theory calculations reveal that the active open‐shell effect from the P‐3p band not only promotes Rh‐4d for increased proton–electron charge exchange but also provides excellent p–p overlapping to locate the O‐related species as distributary center, which can benefit the HER process in alkaline media. It is also demonstrated that the present wrinkled, ultrathin Rh2P nanosheets are highly efficient and durable electrocatalysts toward HER in both acid and neutral electrolytes. The present work opens a new material design for ultrathin 2D metal phosphide nanostructures for the purpose of boosting HER performance at all pHs.

A Generalized Strategy for the Synthesis of Large-Size Ultrathin Two-Dimensional Metal Oxide Nanosheets.

Two-dimensional (2D) nanomaterials show unique electrical, mechanical, and catalytic performance owing to their ultrahigh surface-to-volume ratio and quantum confinement effects. However, ways to simply synthesize 2D metal oxide nanosheets through a general and facile method is still a big challenge. Herein, we report a generalized and facile strategy to synthesize large-size ultrathin 2D metal oxide nanosheets by using graphene oxide (GO) as a template in a wet-chemical system. Notably, the novel strategy mainly relies on accurately controlling the balance between heterogeneous growth and nucleation of metal oxides on the surface of GO, which is independent on the individual character of the metal elements. Therefore, ultrathin nanosheets of various metal oxides, including those from both main-group and transition elements, can be synthesized with large size. The ultrathin 2D metal oxide nanosheets also show controllable thickness and unique surface chemical state.

A Generalized Strategy for the Synthesis of Large‐Size Ultrathin Two‐Dimensional Metal Oxide Nanosheets

AbstractTwo‐dimensional (2D) nanomaterials show unique electrical, mechanical, and catalytic performance owing to their ultrahigh surface‐to‐volume ratio and quantum confinement effects. However, ways to simply synthesize 2D metal oxide nanosheets through a general and facile method is still a big challenge. Herein, we report a generalized and facile strategy to synthesize large‐size ultrathin 2D metal oxide nanosheets by using graphene oxide (GO) as a template in a wet‐chemical system. Notably, the novel strategy mainly relies on accurately controlling the balance between heterogeneous growth and nucleation of metal oxides on the surface of GO, which is independent on the individual character of the metal elements. Therefore, ultrathin nanosheets of various metal oxides, including those from both main‐group and transition elements, can be synthesized with large size. The ultrathin 2D metal oxide nanosheets also show controllable thickness and unique surface chemical state.

Preparation of Ultrathin Two‐Dimensional TixTa1−xSyOz Nanosheets as Highly Efficient Photothermal Agents

AbstractAlthough two‐dimensional (2D) metal oxide/sulfide hybrid nanostructures have been synthesized, the facile preparation of ultrathin 2D nanosheets in high yield still remains a challenge. Herein, we report the first high‐yield preparation of solution‐processed ultrathin 2D metal oxide/sulfide hybrid nanosheets, that is, TixTa1−xSyOz (x=0.71, 0.49, and 0.30), from TixTa1−xS2 precursors. The nanosheet exhibits strong absorbance in the near‐infrared region, giving a large extinction coefficient of 54.1 L g−1 cm−1 at 808 nm, and a high photothermal conversion efficiency of 39.2 %. After modification with lipoic acid‐conjugated polyethylene glycol, the nanosheet is a suitable photothermal agent for treatment of cancer cells under 808 nm laser irradiation. This work provides a facile and general method for the preparation of 2D metal oxide/sulfide hybrid nanosheets.

Preparation of Ultrathin Two-Dimensional Tix Ta1-x Sy Oz Nanosheets as Highly Efficient Photothermal Agents.

Although two-dimensional (2D) metal oxide/sulfide hybrid nanostructures have been synthesized, the facile preparation of ultrathin 2D nanosheets in high yield still remains a challenge. Herein, we report the first high-yield preparation of solution-processed ultrathin 2D metal oxide/sulfide hybrid nanosheets, that is, Tix Ta1-x Sy Oz (x=0.71, 0.49, and 0.30), from Tix Ta1-x S2 precursors. The nanosheet exhibits strong absorbance in the near-infrared region, giving a large extinction coefficient of 54.1 L g-1 cm-1 at 808 nm, and a high photothermal conversion efficiency of 39.2 %. After modification with lipoic acid-conjugated polyethylene glycol, the nanosheet is a suitable photothermal agent for treatment of cancer cells under 808 nm laser irradiation. This work provides a facile and general method for the preparation of 2D metal oxide/sulfide hybrid nanosheets.