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In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. Covalent organic frameworks COFs have been attracting intense research due to their permanent porosity, designable architecture, and high stability. However, COFs are challenging to crystallize and their synthesis often results in tiny crystal sizes and low crystallinities, which hinders an unambiguous structure determination.
The resulting model is comparable to that obtained from high-crystallinity samples by dual-space method. Moreover, for low-resolution 3DED data, the model obtained by SA shows a better framework than those provided by classic direct method, dual-space method, and charge flipping. We further simulate data with different resolutions to understand the reliability of SA under different crystal quality conditions. The successful determination of Py-1P structure by SA compared to other methods provides new knowledge for using 3DED to analyze low-crystallinity and nanosized materials.
Covalent organic frameworks COFs are crystalline porous polymers that are constructed by connecting organic monomers via strong covalent bonds 1 , 2. Their precise integration of organic units at an atomic level to create predesigned framework structures endows them as a promising class of materials in various applications such as gas sorption 3 , 4 , separations 5 , 6 , 7 , catalysis 8 , 9 , 10 , 11 , sensing 12 , optics 13 , 14 , electronics 15 , 16 , 17 , etc.
A grand challenge in the development of COFs is to characterize their structures at the atomic level. Single-crystal X-ray diffraction is the common method used to study crystal structures. While different strategies have been developed to obtain COF single-crystals 18 , 19 , however, limited by the reaction kinetics and thermodynamics of polymerization, the synthesis of COFs often yields low-crystallinity products with small particle sizes. This hinders the determination of COF structures and prevents a deep understanding of their structure—property relationships.
