The rational construction of covalent or noncovalent organic two-dimensional nanosheets is a fascinating target because of their promising applications in electronics, membrane technology, catalysis, sensing, and energy technologies. Herein, a large-area (square millimeters) and free-standing 2D supramolecular polymer (2DSP) single-layer sheet (0.7-0.9 nm in thickness), comprising triphenylene-fused nickel bis(dithiolene) complexes has been readily prepared by using the Langmuir-Blodgett method. Such 2DSPs exhibit excellent electrocatalytic activities for hydrogen generation from water with a Tafel slope of 80.5 mV decade(-1) and an overpotential of 333 mV at 10 mA cm(-2) , which are superior to that of recently reported carbon nanotube supported molecular catalysts and heteroatom-doped graphene catalysts. This work is promising for the development of novel free-standing organic 2D materials for energy technologies.

One of the key challenges in two-dimensional (2D) materials is to go beyond graphene, a prototype 2D polymer (2DP), and to synthesize its organic analogues with structural control at the atomic- or molecular-level. Here we show the successful preparation of porphyrin-containing monolayer and multilayer 2DPs through Schiff-base polycondensation reaction at an air–water and liquid–liquid interface, respectively. Both the monolayer and multilayer 2DPs have crystalline structures as indicated by selected area electron diffraction. The monolayer 2DP has a thickness of∼0.7 nm with a lateral size of 4-inch wafer, and it has a Young's modulus of 267±30 GPa. Notably, the monolayer 2DP functions as an active semiconducting layer in a thin film transistor, while the multilayer 2DP from cobalt-porphyrin monomer efficiently catalyses hydrogen generation from water. This work presents an advance in the synthesis of novel 2D materials for electronics and energy-related applications.

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Despite rapid progress in recent years, it has remained challenging to prepare crystalline twodimensional polymers. Here, we report the controlled synthesis of few-layer 2D polyimide crystals on the water surface, through reaction between amine and anhydride monomers, assisted by surfactant monolayers. We obtained 2D polymers with high crystallinity, a thickness of approximately 2 nm, and an average crystal domain size of around 3.5 μm 2. The molecular structure of the materials, their grain boundaries, and their edge structures were characterized using X-ray scattering and transmission electron microscopy techniques, and supported by computations. The formation of crystalline polymers is attributed to the preorganization of monomers at the water-surfactant interface. Depending on its polar head, the surfactant promoted the arrangement of the monomers-and in turn their polymerizationeither horizontally or vertically with respect to the water surface. The latter was observed with a surfactant bearing a carboxylic acid group, which anchored amine monomers vertically through a condensation reaction. In both instances, micrometre-sized 2D polyamide crystals were grown.

Sheets and rational synthesis are not like fire and water! Hexafunctional terpyridine monomers can be laterally connected by metal salts to result in a mechanically stable, sheetlike entity that can be transferred from the air/water interface to a solid substrate (see the folded, ca. 1.4 nm thin film) and spanned over micrometer‐sized holes. This result is considered an important step on the way to 2D polymers.