Chemistry in 2D

Organic 2D materials display valuable properties that are unique from their bulk counterparts, but creating covalent sheets with long-ranging order remains a formidable challenge. Now, reacting complementary monomers right below a surfactant monolayer on water proves to be a powerful method to create organic 2D materials with long-range order.

Organic materials are highly sensitive to electron beam irradiation and thus easily damaged upon imaging by electron microscopy. Now, low-dose aberration-corrected high resolution transmission electron microscopy allows for less invasive near-atomic-scale imaging of a two-dimensional polymer.

Exfoliation of layered materials is a common route to 2D materials. Here an amorphous copolymer of benzoquinone and pyrrole is exfoliated to yield an active HER catalyst.

Two-dimensional covalent organic frameworks (2D COFs) are commonly synthesised through dynamic covalent chemistry, as it allows for thermodynamic ‘error correction' which enhances crystallinity. Here a crystalline 2D COF with amine and hydroxyl functional groups within the pores is synthesised through kinetically-controlled reactions.

The exfoliation of covalent organic frameworks is a potential route to interesting two-dimensional materials. Here, the authors report a strategy incorporating metal ions and axial ligands to facilitate exfoliation of porphyrin COFs, and examine the photocatalytic activity of the resulting nanomaterials.

Graphene-based materials are widely studied in biomedical applications, but a full picture of their interactions with proteins and cells remains elusive. Here the molecular basis for the effect of graphene-based materials on cell fate and in tissue engineering is reviewed.

The bottom-up synthesis of extended aromatic hydrocarbons can yield curved ‘nanographenes’ with striking properties. Here, the authors review the synthetic advances towards extended corannulenes since 2006, and highlight key challenges facing researchers in the field.

There is a continuous demand to develop new procedures for the synthesis of pristine graphene for device applications. Here the authors report gold catalyzed in situ formation of graphene from hydrocarbon contaminants in a transmission electron microscope within a few milliseconds at room temperature.

Self-driven synthetic microswimmers typically move continuously until the fuel runs out. Here, multilayer graphene oxide particles are shown to periodically swarm together under continuous UV illumination.

Hydrogen peroxide is an industrially highly demanded chemical, but its electrochemical synthesis still suffers from sluggish kinetics and imperfect selectivity. Here, the authors report a catalyst material comprising single cobalt atoms anchored on oxygen functionalized graphene oxide that produces 1.0 mg cm⁻² h⁻¹ of H₂O₂ with high selectivity and a low onset potential.

Carbon-based materials such as graphene oxide are promising catalysts but are often incompatible with high temperatures or microwave irradiation. Here asphaltene oxide is shown to catalyze transformations that range from Claisen-Schmidt and aldol condensations to C–C cross-couplings and microwave-promoted Fischer indole syntheses.

The mechanism underlying synergistic interactions between metal nanoparticles and graphene is poorly understood but has implications for catalytic applications. Here, the authors describe an interface dipole layer catalytic mechanism induced by the interaction between graphene and nickel nanoparticles.

Due to loss of sulfur to the electrolyte, maintaining high charge cycle stability is a key challenge for lithium sulfur batteries. Here a highly stable cathode material is obtained through molybdenum sulfide particle loading on a laser synthesised S- and N-doped graphene electrode.

Rechargeable sodium ion batteries are a promising alternative to lithium technologies, however there are fewer high-performing anode materials. Here, the authors prepare a cobalt-doped tin disulfide/reduced graphene oxide nanocomposite and demonstrate its enhanced sodium kinetics and improved rate performance.

Environmentally friendly binders for energy materials may improve sustainability, but can suffer from poor performance. Here a gel derived from graphene oxide and starch is used as a hybrid binder for supercapacitors, providing good rate performance and stability over 17,000 cycles.

Flexible, transparent supercapacitor electrodes are promising materials for innovative electronic and display applications. Here, the authors report a leaf-skeleton inspired core-shell network that exhibits up to 88% optical transmittance and is stable over 30000 bend-release cycles while retaining competitive electrochemical performance.

Several rare earth carbides are superconducting at ambient pressure and low temperature. Here global structure searching predicts high-pressure metallic phases of yttrium dicarbide with phonon-mediated superconductivity and increased carbon network evolution from dimers to sheets with increasing pressure.

Improving the synthesis of crystalline monolayer transition metal dichalcogenides requires insight into domain and boundary structures. Here, the authors produce monolayer rhenium diselenide by chemical vapour deposition onto gold foil, allowing in situ analysis of domain and defect structure.

Rhenium disulfide is a promising lithium ion battery material but its distorted structure makes computational modelling challenging. Here hardware-accelerator-assisted high-throughput DFT based structure searching is used to model the reversible lithiation of ReS₂ including metal–sulphur bond cleavage.

Metal-organic frameworks are candidates for future energy storage materials, but are limited by poor conductivity and random crystal orientation on current collectors. Here, fabrication of electrodes containing uniformly oriented crystals supported by carbon nanowalls leads to improved electrochemical performance.

Lithium oxygen batteries are prone to degradation resulting from the applied overpotential. Here the surface functionalisation of titanium nitride and carbide MXenes is studied theoretically and shown to reduce the overpotential by up to 80% and to enhance ORR by a factor of 60 compared to common graphene-based catalysts.

Collision geometries are hard to control, making transition states in chemical reaction hard to study. Here the authors show that a linear transition state leads to formation of reaction product ‘knocked-on’ along the continuation of the direction of reagent approach.

Rutile TiO₂ is a prominent photocatalyst for overall water splitting, but the on-surface activation of hydrogen atoms is still not fully understood. Here, the authors use atomic force and kelvin probe force microscopy to study the lateral manipulation of hydrogen on a rutile (110) surface.

Catalytically active complexes adsorbed to noble metal surfaces hold potential for CO₂ utilisation. Here, the mechanism of growth of fac-Re(bpy)(CO)₃Cl on Ag(001) is shown to begin at well-oriented surface steps, with surface restructuring promoting the growth of long-range ordered assemblies.

Mechanistic insight into enantioselective reactions at intrinsically chiral surfaces can be challenging to obtain. Here the catalytic activity of Pd₁- and Pd₃-terminated PdGa{111} surfaces is shown to differ substantially, with Pd₁-terminated surfaces promoting on-surface azide– alkyne cycloadditions enantioand regioselectively.

Ullmann-type reactions on metal surfaces are widely studied examples of on-surface synthesis. Here the combination of normal incidence X-ray standing wave analysis, X-ray photoelectron spectroscopy, and scanning tunneling microscopy enables the characterisation of molecular conformations in two such reactions.

Strong spin-spin interactions between surface-deposited magnetic molecules are desirable for quantum computing applications. Here the authors use scanning tunneling microscopy and spectroscopy to investigate the spin-spin interactions between neighbouring porphyrazine-derivatives on Au(111).

Kinetic control of self-assembly at interfaces offers a promising route to new two dimensional materials. Here high-resolution dynamic atomic force microscopy experiments combined with DFT calculations reveal the kinetic pathways by which 2,5-dihydroxybenzoic acid sequentially assembles on calcite.

Self-sorting is an attractive approach to produce complex supramolecular systems and materials with controlled structures. Here the authors show geometrical complementarity in the self-sorting behaviour of pentagonal and hexagonal pillararenes on heterogeneous surface through layer-by-layer deposition.

Acenes are a promising class of organic materials with distinctive electronic and optical properties. Here decaazapentacene and octaazatetracenes are prepared and their self-assembly behaviour at different oxidation states is analysed.