The　catalytic　oxidation　reaction　plays　a　pivotal　role　in　scientific　research　and　industrial　applications.　However,　the　development　of　green　catalysts　with　high　conversion　and　selectivity　under　mild　conditions　remains　a　challenging　yet　rewarding　endeavor.　Herein,　a　novel,　stable　four-connected　Hf-based　cationic　metal–organic　framework　(MOF)　PFC-30-Hf,　is　reported　as　a　green　catalyst　for　the　oxidation　of　aniline　to　afford　azoxybenzene.　The　catalytic　reaction　can　proceed　at　room　temperature　using　H2O2　as　the　green　oxidant.　More　strikingly,　the　catalyst　yields　oxidation　products　with　almost　100%　conversion　and　selectivity,　endowing　the　entire　reaction　with　an　isolation-free　feature.　The　enhanced　catalytic　activity　is　attributed　to　the　well-defined　catalytic　microenvironment　created　by　the　Lewis　acidic　Hf4+　metal　clusters,　the　Brønsted　acidic　hydroxyl　groups　on　metal　nodes,　and　the　cationic　ligand　with　enhanced　affinity　for　substrates.　This　synergistic　effect　was　then　evidenced　by　parallel　studies　on　neutral　isoreticular　MOF　PFC-30-Hf-N,　HfO2,　and　Hf6　clusters.　Detailed　mechanistic　investigations　into　the　catalytic　process　revealed　the　occurrence　of　stepwise　oxygen　atom　transfer　and　intermediate　condensation　during　the　reaction.　Furthermore,　PFC-30-Hf　demonstrated　equally　satisfactory　activity　and　isolation-free　merit　for　sulfide　oxidation　to　afford　sulfone,　demonstrating　the　great　potential　of　MOFs　to　engineer　the　catalytic　microenvironment　for　the　pursuit　of　green　and　sustainable　chemistry.　©　2025　Chinese　Chemical　Society.　All　rights　reserved.