M-doped　NH2-MIL-125(Ti)　(M=Pt　and　Au)　were　prepared　by　using　the　wetness　impregnation　method　followed　by　a　treatment　with　H-2　flow.　The　resultant　samples　were　characterized　by　powder　X-ray　diffraction　(XRD),　X-ray　photoelectron　spectroscopy　(XPS),　X-ray　absorption　fine　structure　(XAFS)　analyses,　N-2-sorption　BET　surface　area,　and　UV/Vis　diffuse　reflectance　spectroscopy　(DRS).　The　photocatalytic　reaction　carried　out　in　saturated　CO2　with　triethanolamine　(TEOA)　as　sacrificial　agent　under　visible-light　irradiations　showed　that　the　noble　metal-doping　on　NH2-MIL-125(Ti)　promoted　the　photocatalytic　hydrogen　evolution.　Unlike　that　over　pure　NH2-MIL-125(Ti),　in　which　only　formate　was　produced,　both　hydrogen　and　formate　were　formed　over　Pt-　and　Au-loaded　NH2-MIL-125(Ti).　However,　Pt　and　Au　have　different　effects　on　the　photocatalytic　performance　for　formate　production.　Compared　with　pure　NH2-MIL-125(Ti),　Pt/NH2-MIL-125(Ti)　showed　an　enhanced　activity　for　photocatalytic　formate　formation,　whereas　Au　has　a　negative　effect　on　this　reaction.　To　elucidate　the　origin　of　the　different　photocatalytic　performance,　electron　spin　resonance　(ESR)　analyses　and　density　functional　theory　(DFT)　calculations　were　carried　out　over　M/NH2-MIL-125(Ti).The　photocatalytic　mechanisms　over　M/NH2-MIL-125(Ti)　(M=Pt　and　Au)　were　proposed.　For　the　first　time,　the　hydrogen　spillover　from　the　noble　metal　Pt　to　the　framework　of　NH2-MIL-125(Ti)　and　its　promoting　effect　on　the　photocatalytic　CO2　reduction　is　revealed.　The　elucidation　of　the　mechanism　on　the　photocatalysis　over　M/NH2-MIL-125(Ti)　can　provide　some　guidance　in　the　development　of　new　photocatalysts　based　on　MOF　materials.　This　study　also　demonstrates　the　potential　of　using　noble　metal-doped　MOFs　in　photocatalytic　reactions　involving　hydrogen　as　a　reactant,　like　hydrogenation　reactions.