Photocatalytic　CO2　reduction　conjugated　with　H2O　oxidation　is　regarded　as　a　promising　artificial　photosynthesis　system　because　it　can　simultaneously　solve　energy　and　environment　problems.　Here,　a　novel　solid　solution,　Zn2Ti1-xGexO4　(0　＜=　x　＜=　0.15),　with　high　photocatalytic　activity　for　the　reaction　was　successfully　synthesized　via　a　facile　molten　salts　route.　The　Zn-based　solid　solutions　with　size　about　200　nm　have　a　homogeneous　inverted　cubic　spinel　structure　(Fd3m)　and　a　continuously　modulated　band　gap　with　the　Ge　content.　For　the　CO2　reduction　reaction　with　H2O　under　simulated　solar　irradiation,　the　Zn2Ti1-xGexO4　solid　solutions　display　not　only　high　activity　for　the　conversion　of　CO2　into　CH4　and　CO　fuels,　but　also　long-term　stability　(＞60　h　of　catalytic　reaction).　Experimental　results　and　theoretical　calculations　indicated　that　the　conduction　and　the　valence　bands　of　the　cubic　spinet　Zn2TiO4　are　positively　shifted　by　introducing　Zn2GeO4　with　a　pseudocubic　inverse　spinel　structure,　but　the　band　gaps　of　solid　solutions　are　simultaneously　modulated　with　the　introduction　of　germanium.　Nevertheless,　the　Zn2TiO4　affords　a　light-carrier　effective　mass　and　strong　electron　delocalization　by　forming　a　solid　solution　with　Zn2GeO4,　which　is　beneficial　to　improving　migration　of　photogenerated　electrons　and　holes.　As　a　synergistic　result　of　band　gap　narrowing　and　high　carrier　diffusion,　good　conversion　efficiencies　for　production　of　solar　fuels　through　the　reactions　of　CO2　reduction　with　H2O　are　achieved.　(C)　2019　Elsevier　Inc.　All　rights　reserved.