Metal-organic　frameworks　(MOFs)　have　been　demonstrated　as　excellent　host　matrices　to　encapsulate　diverse　guest　molecules　for　fabricating　functional　composite　materials.　Many　synthetic　methods　have　been　explored　to　prepare　white　light　emitting　(WLE)　MOF　composites;　however,　yielding　easily　solution-processable　WLE　guest@MOF　nanocomposites　remains　a　great　challenge.　In　this　work,　we　develop　a　novel　strategy,　i.e.,　in　situ　guest-introduction　combined　with　the　instant　in　situ　exfoliation　method,　to　fabricate　WLE　MOF　composite　nanosheets,　which　integrates　the　advantages　of　bottom-up　synthesis　and　top-down　exfoliation.　By　employing　this　strategy,　the　WLE　lanthanide　hydrate@2D　MOF　composite　nanosheets　with　large　average　lateral　dimensions　of　similar　to　1.2　mu　m　x　500　nm　and　a　thickness　of　similar　to　11.4　nm　are　rapidly　constructed　from　2D　MOF　precursors　and　lanthanide　hydrate　species　in　high　yields.　The　white　light　can　be　finely　tuned　by　adjusting　the　content　of　the　included　guest　molecules,　and　the　color-rendering　index　(CRI)　reaches　up　to　92.　This　novel　synthetic　strategy　has　many　advantages　including　high　efficiency,　facile　and　green　synthesis,　etc.　The　combined　bottom-up　and　top-down　strategy　paves　a　new　route　to　design　and　prepare　functional　guest@2D　MOF　composite　nanosheets.