Increase　of　porosity　and　functionalization　with　nanoscale　catalysts　are　two　significant　aspects　for　achieving　high-performance　metal　oxide-based　resistive　gas　sensors.　In　this　work,　a　simple　metal-organic　framework　(MOF)　route　has　been　developed　to　fabricate　Ag　nanocatalysts　functionalized　ZnO　hollow　nanocages　(NCs).　Nanoscale　Ag　catalysts　with　a　small　size　of　approximately　10　nm　are　uniformly　encapsulated　within　the　cavities　of　MOFs　(ZIF-8).　The　high　porosity,　hollow　structure,　and　functionalization　with　uniformly-distributed　nanoscale　Ag　catalysts　have　been　simultaneously　achieved　for　MOF-derived　ZnO.　This　type　of　porous　Ag-ZnO　hollow　NCs　show　much　enhanced　ethanol　sensing　performances　and　reduced　operating　temperature　in　comparison　with　pure　ZnO　nanoparticles　(NPs)　and　ZnO　NCs.　In　particular,　the　1　mL　Ag-ZnO　NCs　exhibit　the　highest　response　of　84.6-100　ppm　ethanol　at　250　degrees　C,　which　is　6.4　and　3.3　times　higher　than　those　of　pure　ZnO　NPs　and　ZnO　NCs　at　the　optimum　operating　temperature　of　275　degrees　C,　respectively.　The　Ag-ZnO　NCs　also　display　fast　response/recovery　times,　good　ethanol　selectivity,　and　response　reproducibility.　The　enhanced　ethanol　sensing　properties　are　attributed　to　the　synergistic　effects　of　several　points　including　the　electron　sensitization　effects　and　catalytic　effects　of　nanoscale　Ag　catalysts,　porous　and　hollow　structures,　high　surface　area,　and　high　surface　O-　species　absorbing　capability　of　Ag-ZnO　NCs.