Hydrogen-bond-mediated quasi-two-dimensional covalent organic frameworks for ultrahigh gold extraction

Covalent organic frameworks (COFs) are ideal for precious metal recovery due to their high surface areas and tunable binding sites. However, the confinement of binding sites within inner pores often leads to restricted mass transfer, resulting in poor site accessibility and limited extraction capacities. Herein, we report a quasi-two-dimensional (quasi-2D) topology-directed strategy to construct exposed binding sites for highly efficient gold recovery. By incorporating outward-pointing hydroxyl groups, the local conformation of the imine-linked skeleton is effectively locked via inter-chain hydrogen bonding (ICHB), which suppresses molecular torsion and promotes ordered assembly of the 1D chains into a quasi-2D crystalline architecture. This structural rigidification creates unobstructed ion-diffusion pathways and maximizes the exposure of active sites for rapid [AuCl4]− capture and reduction. Remarkably, under mild thermal and vibratory stimulation, gold nanoparticles form in situ and aggregate, yielding a high gold extraction capacity of 5082.32 mg g−1. Theoretical calculations demonstrate that ICHB-induced structural planarization creates a cooperative coordination environment and optimizes the energetic landscape for dechlorination, synergistically promoting guest enrichment and interfacial gold reduction. This work establishes a new blueprint for creating COFs with exposed active sites via inter-chain assembly, offering a scalable approach to maximize site accessibility and electron transfer for selective gold capture. Covalent organic frameworks are ideal for precious metal recovery but the confinement of binding sites within inner pores often leads to restricted mass transfer and limits extraction capacities. Here, the authors report a quasi-2D topology-directed strategy to construct exposed binding sites for highly efficient gold recovery.