Heterogeneous　metal　catalysts　with　bifunctional　active　sites　are　widely　used　in　chemical　industries.　Although　their　improvement　process　is　typically　based　on　trial-and-error,　it　is　hindered　by　the　lack　of　model　catalysts.　Herein,　we　report　an　effective　vacancy-pair　capturing　strategy　to　fabricate　12　heterogeneous　binuclear-site　catalysts　(HBSCs)　comprising　combinations　of　transition　metals　on　titania.　During　the　synthesis　of　these　HBSCs,　proton-passivation　treatment　and　step-by-step　electrostatic　anchorage　enabled　the　suppression　of　single-atom　formation　and　the　successive　capture　of　two　target　metal　cations　on　the　titanium-oxygen　vacancy-pair　site.　Additionally,　during　acetylene　hydrogenation　at　20　degrees　C,　the　HBSCs　(e.g.,　Pt1Pd1-TiO2)　consistently　generated　more　than　two　times　the　ethylene　produced　by　their　single-atom　counterparts　(e.g.,　Pd1-TiO2).　Furthermore,　the　Pt1Pd1　binuclear　sites　in　Pt1Pd1-TiO2　were　demonstrated　to　catalyze　C2H2　hydrogenation　via　a　bifunctional　active-site　mechanism:　initially　C2H2　chemisorb　on　the　Pt1　site,　then　H2　dissociates　and　migrates　from　Pd1　to　Pt1,　and　finally　hydrogenation　occurs　at　the　Pt1-Pd1　interface.