Selective　aerobic　oxidation　of　n-butane　is　one　of　the　most　complex　selective　aerobic　oxidation　reactions　but　is　of　great　importance　in　producing　maleic　anhydride　(MA)　as　a　versatile　chemical　intermediate/plat-form　in　the　chemical　industry.　Supported　VOx　catalysts　are　extensively　used　in　the　selective　oxidation　of　alkanes.　However,　the　identification　of　active　sites　is　quite　challenging　since　various　VOx　structures　(sin-gle　sites,　clusters,　nanoparticles,　and　crystals)　and　the　related　surface　functional　groups　(V　=　O,　V-O-V,　and　V-OH)　can　be　formed　on　the　surface.　By　simply　tuning　the　V/Al　ratios　of　V/Al2O3　catalysts,　we　prepared　various　VOx　structures　using　flame-spray　pyrolysis　and　investigated　their　activities　in　the　selective　oxi-dation　of　n-butane　to　MA.　The　presence　of　single-site　VOx　(SSV),　polymeric　VO4　species,　crystalline　AlVO4　clusters,　and　vanadium　oxide　is　probed　by　systematic　studies　using　51V　and　27Al　solid-state　NMR　spectroscopy　and　confirmed　by　XRD,　HRTEM,　Raman,　and　UV-vis　spectroscopies.　VOx　single-sites　interacting　with　surface　penta-coordinated　Al　(AlV)　sites　are　identified　as　active　sites　promoting　the　con　-version　of　n-butane　to　MA.　V/Al2O3　with　a　high　population　of　SSV-AlV　pairs　in　the　amorphous　Al2O3　net-work　provides　the　best　performance　compared　to　other　V/Al2O3　catalysts　and　those　reported　in　the　literature.　Finally,　a　reaction　mechanism　based　on　the　concerted　action　of　SSV-AlV　pairs　is　proposed.(c)　2022　Published　by　Elsevier　Inc.