Abstract

Two-dimensional polymers (2DPs) refer to a type of organic 2D crystals, comprising repeated organic building blocks connected by strong covalent or coordination bonds in two dimensions, such as 2D COFs and 2D MOFs. Recently, we have developed a surfactant monolayer-assisted on-water synthesis method for the construction of 2DPs, like imine-, imide- and boronate ester-based 2D COFs, which exhibit few-layers and micrometer-sized single-crystalline domains (up to 150 μm2). Besides the dynamic reversible covalent chemistry, we have extended this on-water synthesis to the synthesis of charged 2D poly(pyridinium salt) single crystals on the water surface through an irreversible Katritzky reaction under pH control, which acted as an anion-selective membrane for osmotic energy generation, offering a high chloride ion selectivity and high power density (up to 150 W/m2). Thus, we were able to address the key challenges for ionic transport referring to the contradiction lying in "high stability-high crystallinity" and "high ion permeability-high selectivity". Besides ionic transport, we have also pushed the development of conductive 2DPs for electronics. For instance, one representative iron-bis(dithiolene) 2D c-MOF film exhibited as a p-type semiconductor with a band-like transport and high mobility of ~220 cm2/Vs. Another BBL-based 2DP film also exhibited a p-type semiconducting behavior with a narrow band gap (1.3 eV), and a high THz mobility over 103 cm2/Vs. Very recently, we have applied the on-water synthesis to prepare polyaniline film, and achieved topologically guided 2D polymerization of aniline, which resulted in multi-layer stacked 2D polyaniline single crystals. We discovered its strong out-of-plane electron coupling effect, and demonstrated its metal behavior, which realized 3D electron transport in organic systems. Thus, due to precise topological structures, tunable band gaps, controllable active sites and high carrier transport abiblity, the achieved 2DPs show superior performance in FETs, photo-detecting, chemiresistive sensing and electrochemical energy storage and conversion.

Keywords: 2D polymers; electron transport; ion transport; electrochemical energy

References:
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