Overall　photocatalytic　conversion　of　CO2　and　pure　H2O　driven　by　solar　irradiation　into　methanol　provides　a　sustainable　approach　for　extraterrestrial　synthesis.　However,　few　photocatalysts　exhibit　efficient　production　of　CH3OH.　Here,　BiOBr　nanosheets　supporting　atomic　Cu　catalysts　for　CO2　reduction　are　reported.　The　investigation　of　charge　dynamics　demonstrates　a　strong　built-in　electric　field　established　by　isolated　Cu　sites　as　electron　traps　to　facilitate　charge　transfer　and　stabilize　charge　carriers.　As　result,　the　catalysts　exhibit　a　substantially　high　catalytic　performance　with　methanol　productivity　of　627.66　mu　mol　g(catal)(-1)　h(-1)　and　selectivity　of　approximate　to　90%　with　an　apparent　quantum　efficiency　of　12.23%.　Mechanism　studies　reveal　that　the　high　selectivity　of　methanol　can　be　ascribed　to　energy-favorable　hydrogenation　of　*CO　intermediate　giving　rise　to　*CHO.　The　unfavorable　adsorption　on　Cu-1@BiOBr　prevents　methanol　from　being　oxidized　by　photogenerated　holes.　This　work　highlights　the　great　potential　of　single-atom　photocatalysts　in　chemical　transformation　and　energy　storage　reactions.