Hollow　metal-organic　frameworks　(MOFs)　are　of　considerable　research　interest,　but　they　usually　contain　only　a　single　chemical　component,　and　their　spherical　or　randomly　distributed　voids　may　not　have　ideal　properties.　In　this　work,　we　found　that　incorporating　WO42−　ions　into　UiO-66　could　realize　a　fine　caving　of　the　single　crystals,　which　created　W/UiO-66　nanocages　with　an　uncommon　and　well-defined　channel　structure.　Inspiringly,　the　width　of　the　channel　could　be　tuned　on　the　nanoscale　(80-140　nm)　by　varying　the　dose　of　WO42−　in　the　etching　reaction.　Despite　the　accommodation　of　abundant　W,　the　as-formed　nanocages　were　of　high　crystallinity,　which　was　confirmed　by　HRTEM　images　collected　using　a　K2IS　direct-detection　electron-counting　camera.　As　a　result,　the　channel　structure,　which　was　well　preserved　after　annealing,　and　the　incorporation　of　W　endowed　the　calcined　W/UiO-66　nanocages　with　highly-improved　activity　in　the　oxygen　reduction　reaction　(ORR).　This　synthetic　strategy　could　also　be　applied　to　creating　Mo-bearing　UiO-66　nanocages,　and　may　inspire　the　rational　design　of　other　intricate　MOFs.　©　The　Royal　Society　of　Chemistry.