Construction of Covalent Organic Frameworks via Three-Component One-Pot Strecker and Povarov Reactions

Abstract

Postsynthetic modification (PSM) has been demonstrated to be a powerful method for achieving new covalent organic frameworks (COFs) via single-step or multistep organic functional group transformations on established COF frameworks. PSM, however, might sometimes lead to collapse of the COF framework, decreases in crystallinity, or low postsynthetic yield due to the inherent limit of solid-state synthesis. Herein we report, for the first time, a new synthetic strategy that can generate new COFs via multicomponent one-pot in situ reactions. In total, 12 α-aminonitrileand quinoline-linked COFs with high crystallinity and permanent porosity are successfully achieved by three-component one-pot in situ Strecker and Povarov reactions under solvothermal conditions in high yields. The obtained COFs feature the same structures as those obtained from the stepwise PSM approach on an established imine-linked COF. This in situ multicomponent assembly strategy, as a synthetic methodology parallel to PSM, might open a new route for constructing COFs that is not possible under PSM conditions.

Imparting multi-functionality to covalent organic framework nanoparticles by the dual-ligand assistant encapsulation strategy

“…1h ). The strong diffraction peaks at 2.72, 4.81, 5.63, 7.39 and 9.65° can be clearly observed after the thermal treatment in the acetic acid condition, matching well with (100), (110), (200), (210), and (220) planes of TAPB-DMTP-COF, respectively 32 . It should be noticed that the shell is amorphous within the first 4 h reaction under room temperature, and the diffraction peaks emerge after only 2 h thermal treatment at 80 °C (Supplementary Fig.…”

Chemical Conversion and Locking of the Imine Linkage: Enhancing the Functionality of Covalent Organic Frameworks

“…[50] A multi-component OPR version of the Strecker synthesis was developed to form stable aaminonitrile-linked COFs. [51] The three-component reaction was carried out by dissolving the amine and the aldehyde buildingblocks with trimethylsilyl cyanide (TMSCN) in 1,2dichlorobenzene (o-DCB)/1-butanol (n-BuOH) mixture and using standard solvothermal conditions with the assistance of acetic acid and BF3•OEt2. The resulting a-aminonitrile-linked S-TmTaDm-COF and other COFs were synthesized with this method demonstrating its general applicability.…”

“…As discussed in the previous section, upon reaction with aryl alkynes or aryl alkynes, the imine linkages in COFs can be converted to yield the corresponding quinoline-linked COFs which features an extended p-electron delocalization. [14,51,57] The reaction is relatively versatile and could be carried out both in its OPR and its PSM versions. The PSM of the pre-synthesized imine COF-1 (Figure 5a) was achieved for the first time by using phenylacetylene at 110 °C in the presence of BF3•Et2O and chloranil in toluene for 3 days (Scheme 4d).…”

“…Noteworthy, it has been recently shown that the multi-component OPR and single-step PSM are potentially interchangeable strategies that can be used to tackle benzothiazole, quinoline and a-aminonitrilelinked COFs. [47,51] To date, however, the PSM product was always found being slightly worse in terms of yield and crystallinity, probably due to the difficulties deriving from the reactions at the solid state. Finally, despite being time demanding, multi-step PSM reactions prepared the ground for the construction of complex moieties at the linkage position of COFs.…”

Homochiral Covalent Organic Frameworks for Asymmetric Catalysis

“…Recently, the COF synthetic methodology has been successfully extended to the in situ reactions of multiple functional groups by Wang et al [40] . and us [19d] . We believe that these one‐pot multifunctional reactions based on the Debus–Radziszewski, Strecker, and Povarov reactions will become a valuable tool not only for the in situ formation of COFs, but also HCCOFs.…”