Improving　product　selectivity　is　the　most　important　goal　for　the　artificial　photosynthesis　of　CO2　and　H2O　considering　that　the　adsorption　behaviors　of　reactants　may　play　an　important　role　in　the　product　selectivity　of　CO2　conversion.　In　this　work,　a　black　In2O3　sample　was　modified　with　fluoride　anions　(F−)　as　electron　donors　or　amino　ions　(NH2+)　as　electron　acceptors.　F-modified　In2O3　provided　additional　F−　and　In2+　sites,　which　promoted　H2O　to　accept　more　electrons　from　the　material,　and　exhibited　a　high　selectivity　to　CH4　of　81.95%.　NH2-modified　In2O3　caused　H2O　to　donate　electrons　to　the　material　by　constructing　a　hydrophobic　layer,　resulting　in　a　high　combined　selectivity　to　methanol　and　carbon　monoxide　of　87.64%.　Based　on　the　two　different　H2O　adsorption　behaviors　at　In2+　sites　adjacent　to　oxygen　vacancy　defects　(VO-In2+)　or　at　In3+　sites,　the　respective　formation　of　hydrogen　ions　(H+)　or　protons　(*H)　is　key　to　regulating　the　product　selectivity　of　CO2　reduction.　The　formation　of　a　confined-space　structure　of　CO2　and　its　capacity　to　accept　more　electrons　from　the　material　induced　by　a　higher　number　of　VO-In2+　sites　after　modification　both　ensure　the　proceeding　of　CO2　reduction.　The　findings　presented　in　this　work　add　to　the　understanding　of　artificial　photosynthesis.　©　2023　The　Royal　Society　of　Chemistry.