This paper introduces a "Cage-on-MOF" strategy to enhance the selectivity of metal-organic frameworks (MOFs) in adsorption and catalysis without compromising porosity. Two types of oppositely charged porous coordination cages (PCCs) with secondary binding groups were synthesized and coordinatively functionalized onto PCN-222 and MIL-101 MOFs. The PCCs act as modulators, tuning surface charge, stability, and adsorption behavior. MOF@PCC nanocomposites showed reversed product selectivity and excellent recyclability in condensation reactions. This strategy offers a new approach to functionalizing porous materials.
