Carbon　nitrides　(g-C3N4)　have　emerged　as　the　promising　photocatalysts　for　CO2　conversion.　However,　they　suffer　from　inefficient　charge　transfer　and　a　lack　of　metal　sites.　Herein,　the　p-type　CoNiO2　nanosheets　are　anchored　on　the　n-type　g-C3N4　microtubes　to　construct　p-n　heterojunction　photocatalysts.　The　CoNiO2　nanosheets　provide　metal　sites　to　bind　and　activate　CO2　molecules,　and　the　configuration　of　p-n　heterojunction　impels　electron-hole　separation.　The　CoNiO2　nanosheets　that　are　vertically　aligned　on　the　surfaces　of　g-C3N4　microtubes　build　a　hierarchical　hollow　structure　and　an　intimate　contact　interface,　which　also　contributes　to　the　CO2　adsorption　and　rapid　migration　of　charged　carriers.　As　a　result,　the　g-C3N4@CoNiO2　p-n　heterojunction　photocatalysts　exhibit　outstanding　yields　(3645　mu　mol　h-1　g-1　of　CO　and　943　mu　mol　h-1　g-1　of　H2)　from　CO2　reduction　under　visible　light　irradiation,　much　higher　than　that　of　pure　CoNiO2　nanosheets　and　g-C3N4　microtubes.　In　situ　DRIFT　spectra　are　performed　to　monitor　the　intermediates　of　CO2　reduction　on　the　surfaces　of　g-C3N4@CoNiO2,　the　results　of　which　confirm　the　adsorption　and　activation　of　CO2　molecules.　It　is　expected　that　this　work　would　provide　a　feasible　strategy　for　designing　high-efficiency　g-C3N4-based　heterojunction　photocatalysts.