Yolk-shell　composites　offer　a　promising　platform　for　integrating　cores　into　hollow　shells　to　create　unique　structures　and　properties.　However,　the　concomitant　functionality　and　tunability　of　yolk-shell　nanocomposites　is　still　a　great　challenge　but　highly　desirable.　Herein,　we　demonstrate　a　rational　design　for　the　fabrication　of　yolk-shell-structured　covalent　organic　framework　(COF)@metal-organic　framework　(MOF)　(YS-COF@MOF)　nanocomposites　with　COF　as　the　external　shell　and　MOF　as　the　inner　yolk.　Series　of　the　YS-COF@MOF　composites　with　different　MOF　cores　and　COF　shells　were　readily　synthesized　via　a　template-free　solvothermal　method.　Control　experiments　showed　that　the　formation　of　the　hollow　cavity　between　the　core　and　the　shell　originated　from　the　amorphous-to-crystalline　transformation　and　the　simultaneous　shrinkage　of　the　shell　under　the　pyrrolidine-catalyzed　conditions.　The　resultant　YS-COF@MOF　merges　the　inherent　structure　tunability　and　functionality　of　both　COFs　and　MOFs.　The　functions　of　YS-COF@MOF　can　be　regulated　and　optimized　by　judicious　selections　of　metal　ions　and　organic　building　blocks.　Representative　YS-TpPa@UiO-66-(COOH)2　with　spatially　distributed　acidic　and　basic　sites　exhibited　synergistically　enhanced　catalytic　activity　in　one-pot　deacetalization-Knoevenagel　cascade　reactions.　©