A Novel Strategy for the Construction of Covalent Organic Frameworks from Nonporous Covalent Organic Polymers

Abstract

The field of covalent organic frameworks (COFs) has been developed significantly in the past decade on account of their important characteristics and vast application potential. On the other hand, the discovery of novel synthetic methodology is still ac hallenging task to further promote the preparation of COFs.H erein, an interesting protocol for the conversion of amorphous nonporous covalent organic polymers (COPs) to COFs was established, affording four COFs with high crystallinity and porosity.S pecifically,i mine-linked amorphous COP-1 was successfully converted to COF-1-4 by replacing one type of linker with other organic building blocks. The realization of this conversion provides afacile method for constructing COFs from COPs.

Construction of a Nanoporous Highly Crystalline Hexagonal Boron Nitride from an Amorphous Precursor for Catalytic Dehydrogenation

“…[16] However, the final few-layered h-BNNS obtained through these approaches often suffer from low surface areas or amorphous/low crystalline structures. [21] Herein, an ovel strategy was developed for the successful transformation of amorphous bulk h-BN to h-BNNS with high crystallinity and porosity,w hich was fully characterized by powder X-ray diffraction (PXRD), microscopy and N 2 adsorption/desorption isotherms.T he essence of this strategy lies in the successive dissolution-precipitation/crystallization of amorphous h-BN precursor in the presence of magnesium ( Figure 1A). [20] In addition, the high crystallinity makes their structures easier to be determined by using powder X-ray diffraction (PXRD) and high-resolution transmission electron microscopy (HR-TEM).…”

“…Recently,t his protocol was utilized in the conversion of amorphous covalent organic polymers (COPs) to COFs of high crystallinity and porosity by replacing the linkers. [21] Herein, an ovel strategy was developed for the successful transformation of amorphous bulk h-BN to h-BNNS with high crystallinity and porosity,w hich was fully characterized by powder X-ray diffraction (PXRD), microscopy and N 2 adsorption/desorption isotherms.T he essence of this strategy lies in the successive dissolution-precipitation/crystallization of amorphous h-BN precursor in the presence of magnesium ( Figure 1A). Thep roduced crystalline h-BNNS consisted primarily of thin layers in ah igh mass yield of 88 %.…”

Construction of Covalent‐Organic Frameworks (COFs) from Amorphous Covalent Organic Polymers via Linkage Replacement

“…ForC OF-3, the value is similar to the material synthesized by the direct approach (1700 m 2 g À1 ), [16] while the value for COF-4 is much higher than that synthesized by the direct method (2238 m 2 g À1 )a nd the COP-to-COF strategy (2143 m 2 g À1 ). [12,17] All these results demonstrated that the linkage replacement from polyimide-based COP-2 to iminebased COF-3 and COF-4 was very successful.…”

“…We thus developed aC OP-to-COF conversion strategy to obtain COFs with high crystallinity and porosity. [12] Current reports on the linker substitution during the construction of COFs are limited to the same type of linkages with the same type of reactions. There is still no report of the linkage substitution using different types of linkages under different types of reactions.…”

“…To realize the linkage replacement from COPs to COFs, COPs based on reversible covalent bonds are suitable starting materials.C onsidering that polyimide bond is less reversible and more stable than imine bond, we firstly selected iminelinked COP-1 as as tudy model and 1,4,5,8-naphthalenetetracarboxylic anhydride (L 1 )a st he replacing linker.C OP-1w as synthesized from 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 1,4-phthalaldehyde under solvothermal conditions. [12] COF-1 was then obtained by substituting the 1,4phthalaldehyde linker in COP-1 with L 1 using N-methyl pyrrolidone (NMP) and mesitylene as the solvent in the presence of isoquinoline (Scheme 1). Thet ransformation from COP-1 to COF-1 was fully characterized by Fouriertransform infrared spectroscopy (FT-IR) and 13 Ccross-polarization magic angle spinning nuclear magnetic resonance (CP/ MAS NMR) spectroscopy.I nF T-IR spectra, the absence of characteristic imine absorption band at 1623 cm À1 and the appearance of the C=Oa bsorption bands at 1680 and 1720 cm À1 indicate the complete transformation from COP-1t oC OF-1 ( Figure S1 in the Supporting Information).…”