Phosphorothioate-Cored Organic Membrane as a Heterogeneous Dip Catalyst for Hydrogen-Bonding-Assisted Covalent Organic Framework Synthesis

Covalent organic frameworks (COFs) are typically catalyzed by acid or base to maintain reversibility during dynamic covalent bond formation. However, the concept of recyclable and linkage-general heterogeneous catalytic systems for COF synthesis seems interesting and has not yet been demonstrated. On this line, we introduce an intrinsic heterogeneous membrane-based “dip-catalyst” for COF synthesis. Wherein a free-standing, interfacially fabricated Schiff-base membrane (TAP–DTP) directly mediates COF formation with good yield. The membrane incorporates a phosphorothioate functionality that promotes a hydrogen-bond-assisted catalytic pathway, which facilitates condensation reactions while preserving the dynamic character required for error correction. Remarkably, this single catalytic platform supports the formation of structurally diverse COFs, including imine-, β-ketoenamine-, and imide linkages, and can be readily retrieved and reused without measurable loss of activity. Control experiments with a phosphorothioate-free analogue confirm the decisive role of the P═S motif, while density functional theory (DFT) calculations substantiate the origin of this catalytic effect. The optimized structures reveal strong hydrogen-bonding interactions between the catalytic core and the amine and carboxylic acid hydrogens (H···S = 2.76 and 2.34 Å), while the aldehyde interaction is weaker (3.09 Å), indicating that the amine and carboxylic acid components primarily facilitate the slow formation of COF. This work establishes a new paradigm in which a heterogeneous, recyclable dip catalyst serves as an alternative to conventional homogeneous systems for COF synthesis, and may be extended to broader organic transformations in the future.