COFs on MOFs: Layer‐by‐Layer Synthesis of MOF@COF Nanoparticles with Synergistic Adsorption

Abstract Synergistic effects between porous materials offer a powerful route to enhance key functionalities such as adsorption, catalysis, and molecular transport. In this context, the combination of metal–organic frameworks (MOFs) and covalent organic frameworks (COFs) provides a promising platform for engineering hybrid adsorbents with synergistic sorption behavior. Here, a versatile layer‐by‐layer strategy is presented for the controlled growth of crystalline COF shells on MOF nanoparticles, yielding uniform MOF@COF nanocomposites as stable aqueous colloids. This approach enables precise tuning of shell thickness and porosity under mild conditions. The resulting core–shell hybrids exhibit enhanced water adsorption, driven by the formation of interfacial mesopores. Modeling studies indicate that a minimum number of COF growth cycles is necessary to induce these mesopores, which interconnect with the intrinsic micropores of the COF shell and facilitate synergistic uptake. This work presents a scalable and modular approach to creating porous hybrid nanoparticles with programmable interfacial architectures and enhanced sorption performance.