Direct conversion of aromatic amides into crystalline covalent triazine frameworks by a condensation mechanism

Abstract

Summary: Multiple studies have recently been conducted to develop well-ordered covalent triazine-based frameworks (CTFs). To date, few studies have demonstrated CTFs with high crystallinity using novel synthesis strategies and different building blocks. To construct highly crystalline CTFs with enhanced performance, significant technical advancements in fundamental chemical insights are essential. Here, we report that the phosphorus pentoxide (P2O5)-catalyzed condensation of biphenyl-based amide and nitrile monomers can produce ordered pCTF-2. The pCTF-2A directly synthesized from amide monomers showed unusually higher crystallinity and porosity than the pCTF-2N synthesized from nitrile monomers. Based on experimental results, density functional theory (DFT) calculations revealed that amide groups can be directly trimerized into triazine rings in the presence of P2O5, which is a more thermodynamically favorable reaction than those from nitrile groups. Based on this mechanistic insight, the efficient and better synthesis strategy provides an effective pathway for the formation of crystalline CTFs.

Keywords

• covalent triazine frameworks
• crystalline organic networks
• cyclotrimerization
• phosphorus pentoxide
• reaction mechanisms