Flexible vs. rigid covalent organic frameworks: catalytic performance in the Knoevenagel reaction†

This study successfully synthesized two distinct covalent organic frameworks (COFs): the rigid DAPO-TFPT-COF and the flexible DAPO-TFPC-COF. Both COFs boast high crystallinity, large specific surface area, and uniform pores. A comprehensive investigation was conducted to evaluate the catalytic performance of rigid versus flexible COFs in the Knoevenagel reaction. Compared to the rigid DAPO-TFPT-COF, the flexible DAPO-TFPC-COF showed superior dispersibility and faster kinetics in solvents, leading to higher catalytic activity; however, its better dispersibility resulted in a lower recovery rate. The flexible COF exhibited lower tolerance in weak acidic and basic environments, indicating the need for developing flexible COFs with stronger bonds. This study is the first to extensively explore the catalytic performance of both rigid and flexible COF catalysts, offering valuable insights for bio-mimetic research. It highlights the potential of flexible COFs, prompting further exploration in bio-mimetic applications.