Covalent Organic Frameworks (COFs) as Multi-Target Multifunctional Frameworks

Abstract

Covalent organic frameworks (COFs), synthesized from organic monomers, are porous crystalline polymers. Monomers get attached through strong covalent bonds to form 2D and 3D structures. The adjustable pore size, high stability (chemical and thermal), and metal-free nature of COFs make their applications wider. This review article briefly elaborates the synthesis, types, and applications (catalysis, environmental Remediation, sensors) of COFs. Furthermore, the applications of COFs as biomaterials are comprehensively discussed. There are several reported COFs having good results in anti-cancer and anti-bacterial treatments. At the end, some newly reported COFs having anti-viral and wound healing properties are also discussed.

Keywords: anticancer; crystallinity; dynamic covalent chemistry; photochemical synthesis; sonochemical synthesis; stability.

Figure 1

(a) Representation of chemical reactions for synthesis of COFs. (b) The combination of monomers to design 2D COFs.

Figure 2

(a) Boron containing COF. (b) Triazine-based COF (CTF) [37]. “Used with permission of Royal Society of Chemistry, from Covalent organic frameworks (COFs): From design to applications. Ding, S.-Y.; Wang, W., Chem. Soc. Rev. 2013, 42, 548–568 in 2022; permission conveyed through Copyright Clearance Center, Inc.”

Figure 3

Imine-based COF having pore size of 3.5 nm.

Figure 4

Coordinative adsorption (a) and ion-exchange method (b) [66].

Figure 5

Major adsorption mechanisms; H-bonding (a), pore-size effect (b), hydrophobic interaction (c), and pi–pi interactions (d).

Figure 6

(a) Quercetin adsorbed on TTI-COF (b) Doxorubicin adsorbed on TAPB-DMTP-COF.

Figure 7

(a) COF LZU-1 with a particle size of 110 nm. (b) BODIPY PS effectively nanosized on LZU-1 nanoparticles [101].

Figure 8

Basic unit (amorphous polyimine) and crystalline COF (Tpbd) “Reproduced with permission of John Wiley and Sons, Angewandte Chemie International Edition from Manipulation of amorphous-to-crystalline transformation: Towards the construction of covalent organic framework hybrid microspheres with NIR photothermal conversion ability by Tan, J.; Namuangruk, S.; Kong, W.; Kungwan, N.; Guo, J.; Wang, C. in Angew. Chem. Int. Ed. 2016, 55, 13979–13984 [108]”.

Figure 9

Combining DOX and TAPB-DMTP-COF. “Reproduced with permission of John Wiley and Sons (Chemistry—A European Journal) from One-Pot Synthesis of DOX@ Covalent Organic Framework with Enhanced Chemotherapeutic Efficacy by Liu, S.; Hu, C.; Liu, Y.; Zhao, X.; Pang, M.; Lin, J. in Chem. A Eur. J. 2019, 25, 4315–4319” [99].

Figure 10

Physical adsorption of a-amylase into the TPMM COF pores “Reprinted from Integration of α-amylase into covalent organic framework for highly efficient biocatalyst, Samui, A.; Sahu, S.K. Microporous and Mesoporous Materials 2020, 291, 109700.” Copyright (2022), with permission from Elsevier [126].

Figure 11

Recycling capability of COF-PY-EDDA and COF-ETTA-EDDA.

Figure 12

Loading of AQS onto GO, resulting in the AQS-GO nanocomposite through π–π interactions. “Reprinted from, Enhanced photo-induced antibacterial application of graphene oxide modified by sodium anthraquinone-2-sulfonate under visible light by Zhang, L.; Chen, P.; Xu, Y.; Nie, W.; Zhou, Y. Applied Catalysis B: Environmental 2020, 265, 118572. Copyright (2022), with permission from Elsevier” [142].

Figure 13

Schematic representation of ACE2 and COF preventing interaction of spike protein with ACE2. “Reprinted from, Atomistic insight into 2D COFs as antiviral agents against SARS-CoV-2. By Jahromi, A.M.; Solhjoo, A.; Ghasemi, M.; Khedri, M.; Maleki, R.; Tayebi, L. Materials Chemistry and Physics 2022, 276, 125382, Copyright (2022), with permission from Elsevier” [156].