Photocatalytic　CO2　conversion　is　a　promising　method　to　yield　carbon　fuels,　but　it　remains　challenging　to　regulate　catalytic　materials　for　enhanced　reaction　efficiency　and　tunable　product　selectivity.　This　study　concerns　the　development　of　a　facile　and　efficient　thermal　post-treatment　method　to　improve　the　crystallinity　and　surface　hydrophobicity　of　a　cobalt　phosphide　(CoP)　cocatalyst,　which　promotes　the　separation　and　transfer　of　photoexcited　charge　carriers,　reinforces　CO2　chemisorption,　and　weakens　the　H2O　affinity.　Compared　with　pristine　CoP,　the　optimal　CoP-600　cocatalyst　displays　a　3.5-fold　enhancement　in　activity　and　a　2.3-fold　increase　in　selectivity　for　the　reduction　of　CO2　to　CO　with　a　high　rate　of　68.1　μmol　h−1.　©　2021　Wiley-VCH　GmbH