Mesoporous　support-encapsulated　fine-size　metal　nanoclustersholdgreat　potential　for　catalytic　applications　by　virtue　of　their　highreactivity　and　fast　mass　transport　kinetics　but　suffer　greatly　fromparticle　aggregation　and/or　sintering,　especially　under　high　reactiontemperatures.　Here,　we　report　an　inner　surface-confinement　strategyto　stabilize　a　variety　of　ultrafine　metal　nanoclusters　(M　=　Pt,　Pd,Ni,　and　Ag)　inside　mesoporous　silica　supports.　The　strategy　is　basedon　the　selective　N　functionalization　of　the　inner　surface　of　mesopores,which　not　only　assures　the　direct　growth　of　ultrafine　metal　nanoclusterstherein　but　also　endows　the　active　metal　nanoclusters　with　excellentthermal　stability　via　N-metal　coordination.　Remarkably,　the　mesopore-encapsulatedN-coordinated　Pt　nanoclusters　are　particularly　selective　for　making　&　alpha;,&　beta;-unsaturated　alcohol,　benefiting　from　their　energeticallyfavored　reaction　pathway　for　end-on　binding　&　alpha;,&　beta;-unsaturatedaldehyde　reactants　and　heterolytic　dissociation　of　hydrogen.　The　syntheticmethodology　is　expected　to　provide　new　guidelines　to　improve　the　thermalstability　of　mesopore-encapsulated　metal　nanoclusters　for　superb　catalysis.