One-pot　synthesis　of　urea　[(NH2)(2)CO]　from　easily　available　small　molecules,　that　is,　N-2,　CO2,　and　H2O,　is　an　extremely　attractive　but　very　challenging　reaction.　2D-CdS@3D-BiOBr　composites　with　S-scheme　heterojunctions　are　constructed　via　a　facile　hydrothermal　technique　followed　by　a　self-assembly　method　and　shown　to　be　an　excellent　photocatalyst　enabling　the　reduction　of　N-2　and　CO2　with　H2O　to　(NH2)(2)CO　under　visible　light.　The　optimal　40%2D-CdS@3D-BiOBr　sample　shows　up　to　15　mu　mol.g(-1).h(-1)　total　yield　of　NH3　and　(NH2)(2)CO,　of　which　(NH2)(2)CO　accounts　for　54%.　The　apparent　quantum　efficiency　(AQE)　is　3.93%　for　urea　production.　On　the　photocatalyst,　urea　is　speculated　to　form　by　two　possible　chemical　routes.　One　is　direct　photocatalytic　synthesis.　Both　N-2　and　CO2　molecules　are　activated　by　the　Cd2+　ion　of　2D-CdS　and　the　oxygen　defect　of　3D-BiOBr　at　the　edges　of　the　heterojunction　interface　of　2D-CdS/3D-BiOBr,　respectively.　*HNCONH*　is　the　key　intermediate　of　the　formation　of　(NH2)(2)CO　molecules.　The　other　is　indirect　synthesis　by　photocatalysis　and　then　thermocatalysis.　N-2　is　reduced　into　NH3　and　CO2　is　reduced　into　CO　on　2D-CdS　by　the　photogenerated　electrons　and　protons,　and　then　the　formed　NH3　reacts　with　the　reactant　CO2　or　the　product　CO　to　form　(NH2)(2)CO　by　thermocatalysis　on　2D-CdS.　The　former　is　dominant　for　urea　synthesis.　The　work　confirms　that　urea　could　be　synthesized　photocatalytically　from　cheap　N-2,　CO2,　and　H2O　under　visible　light.　A　composite　heterojunction　semiconductor　could　be　a　prospective　photocatalyst　appropriate　for　the　complex　reaction.