Metal nanoparticles encased in a MOF shell have shown remarkable properties in catalysis due to potential synergistic effects. However, capping agents, commonly used to prepare these nanoparticles, lower their reactivity once embedded into the MOF. Here we present a new route to prepare polyvinylpyrrolidone (PVP)-capped Au NPs@MOF-808 core–shell composites. Simultaneously, we show for the first time that the capping PVP can be easily removed by chemical treatment while maintaining the integrity of the MOF shell. We finally show how this leads to a significant enhancement of the reactivity of Au NPs@MOF-808 composites for selective oxidation reactions.