Diverse crystal size effects in covalent organic frameworks

Abstract

Crystal size effect is of vital importance in materials science by exerting significant influence on various properties of materials and furthermore their functions. Crystal size effect of covalent organic frameworks (COFs) has never been reported because their controllable synthesis is difficult, despite their promising properties have been exhibited in many aspects. Here, we report the diverse crystal size effects of two representative COFs based on the successful realization of crystal-size-controlled synthesis. For LZU-111 with rigid spiral channels, size effect reflects in pore surface area by influencing the pore integrity, while for flexible COF-300 with straight channels, crystal size controls structural flexibility by altering the number of repeating units, which eventually changes sorption selectivity. With the understanding and insight of the structure-property correlation not only at microscale but also at mesoscale for COFs, this research will push the COF field step forward to a significant advancement in practical applications.

Aqueous Synthesis of Covalent Organic Frameworks as Photocatalysts for Hydrogen Peroxide Production

“…29 The COF-300 synthesized in LC had less overall N 2 uptakes which might be due to its larger crystal size and thus low accessibility of the pores (Figure S17). 34 The reason behind the formation of highly crystalline 2D COFs in ribbon structures and COF-300 in rod with the LC-directed synthesis methodology deserves a discussion. The high crystallinity of the COFs might relate to the strong confinement of the monomers as well as their molecular precursors by the LC, which prevents their rapid agglomeration and diffusion among Triton X-100, n-decyl alcohol and water, slows down the polymerization as well as crystallization rate, leaving enough time and space for the ordering of the final products.…”

Reticular design and crystal structure determination of covalent organic frameworks

“…71 These studies, however, draw our attention to another issue which is the generalizability-the modulator approach up to this point works well only for 3D imine-linked COFs. 72,73 Recently, Yaghi and co-workers have reported single crystals of a 2D BP-COF-6 based on boron-phosphorous linkages; 49 it is likely that the single crystals of BP-COF-6 are in situ formed under acidic conditions and are not applicable to the vast chemistry of COFs based on a variety of linkages (though the formation of BP-COF-6 paves the way for future use of specic linkers that are able to generate organic clusters in situ). At this point, it should be noted that COF chemists are still facing a great challenge with the limitation of COF crystallization, and new chemistry with impactful solutions is highly needed to open the avenue for diversifying COF chemistry.…”

Morphological control of covalent organic frameworks in a PEG–H2O system

“…Although deploying a green medium and environment-friendly synthetic methods has achieved satisfactory advancements, it is still difficult to obtain single uniform and dispersed TAPB–DMTP COFs due to solvent limitations. Accordingly, inspired by the preparation of COFs of LZU-111, LZU-112, LZU-300 and LZU-303 by Wang's group from Lanzhou University, 47 benzaldehyde and aniline were introduced into the reaction system, and spherical TAPB–DMTP COF-4 with a diameter of approximately 400 nm and good dispersion was successfully prepared, as shown in Fig. 5 and Fig.…”