Toward Covalent Organic Framework Metastructures

作者：Song Wang, Yuhao Yang, Haoran Zhang, Ziyang Zhang, Chi Zhang, Xiaodong Huang, Daichi Kozawa, Pingwei Liu, Bo‐Geng Li, Wenjun Wang · 发表于：Journal of the American Chemical Society · 年份：2021 · DOI：10.1021/jacs.0c13090 · 被引用次数：75 · 研究领域：Covalent Organic Framework Applications、Metal-Organic Frameworks: Synthesis and Applications、Luminescence and Fluorescent Materials

The bottom-up assembly of periodically ordered structures provides a scalable way for producing metastructured materials with exotic optical and mechanical properties. However, direct self-assembly of small molecules into such metastructures beyond the nanoscale remains an unresolved issue. Here we demonstrate that metastructured assemblies of two-dimensional (2D) polymers, specifically 2D covalent organic frameworks (COFs), can be directly synthesized in solution. We applied 2D COF monomer polycondensation to prepare flower-shaped particles consisting of highly crystalline “petals” with sizes larger than 20 μm. The petal comprises periodically arranged COF nanoflake units with tunable lengths of 490–850 nm, thicknesses about 20 nm, interflake spacing around 14 nm, and Hermans orientation factors up to 0.998. Such a metastructure is mechanically robust and remains almost intact even after full pyrolysis at 900 °C. It also demonstrates unique birefringence and polarization-dependent resonances under visible–near-infrared light not observed in its constituents, 2D COF polycrystals, and with well-defined nanopores of 1.8 nm and the high surface area of 1576 m 2 /g. Such metastructured particles with nanopores are well-suited as novel particulate optical devices for collecting and storing information about their surroundings that can be easily read out by polarization imaging with high sensitivity, as demonstrated by their explosive detection and anticounterfeiting applications. ...