A Stable, Mesoporous Three-Dimensional Covalent Organic Framework as a Versatile Functional Platform

Introducing functionality into the pore channels of covalent organic frameworks (COFs) without compromising their crystallinity and porosity remains a formidable challenge. Herein, we present a stable, mesoporous 3D COF, JUC-685, which exhibits a surface area of 2,188 m² g^-1 and a pore size of 3.20 nm. This robust structure serves as a versatile platform for constructing functionalized COFs while preserving structural integrity. Using a solvent-assisted linker exchange (SALE) strategy, we successfully incorporated a series of challenging functional moieties-including azobenzene, carbazole, and complex heterocycles-to generate an isoreticular series, JUC-686 to JUC-689. This methodology effectively decouples functionality from structural order. The azobenzene-functionalized derivative, JUC-686, retains a high surface area of 2,131 m² g^-1 and a mesopore of 3.09 nm. Crucially, the photoresponsive azobenzene units within its spacious pores enable remarkable, light-induced modulation of CO₂ adsorption capacity, with a change rate reaching 60.4% under UV irradiation-the highest performance reported for any azobenzene-functionalized porous materials. This work establishes a general platform for the synthesis of highly crystalline COFs with pore-wall functionality, unlocking new opportunities in smart adsorption, catalysis, and beyond.