The　efficiency　of　CO2　photoreduction　is　limited　by　slow　charge　kinetics　and　the　mass　transfer　of　hydrophobic　CO2　and　H2O　over　the　photocatalyst.　Herein,　we　present　a　copper–alkynyl　bond　coordination　polymer　(CA-CP)　with　atomically-dispersed　copper–alkynyl　units　(ADCAUs).　By　incorporating　hydrophobic　CA-CP　with　hydrophilic　iodine　vacancy-rich　bismuth　oxyhalides　(IV-BX),　we　construct　amphiphilic　heterojunction　photocatalysts　(CA-CP/IV-BX)　for　visible-light-driven　CO2　photoreduction.　CA-CP/IV-BX　achieves　excellent　stability,　100　%　CO　selectivity　and　a　CO-evolution　rate　of　157.6　μmol　g−1　h−1　coupled　with　O2　releasing.　Experimental　and　theoretical　calculations　elucidate　that　the　ADCAUs　favor　adsorption　and　activation　of　CO2,　and　have　high　CO　selectivity.　Moreover,　the　amphiphilic　janus　structure　not　only　ensures　the　spatial　synergy　effect　of　CO2　reduction　and　H2O　oxidation,　but　also　promotes　charge　separation　and　proton　feeding,　boosting　CO2　photoreduction　activity.　This　work　develops　Cu–alkynyl　coordination　polymer　photocatalysts　with　ADCAUs　and　provides　insights　into　hydrophobic–hydrophilic　biphasic　photocatalysts　for　synergistic　CO2　reduction　and　H2O　oxidation.　©　2024　Elsevier　B.V.