Photocatalytic　CO2　conversion　with　H2O　to　carbonaceous　fuels　is　a　desirable　strategy　for　CO2　management　and　solar　utilization,　yet　its　efficiency　remains　suboptimal.　Herein,　efficient　and　durable　CO2　photoreduction　is　realized　over　a　Ru-NPs/Ru-PHI　catalyst　assembled　by　anchoring　Ru　single　atoms　(SAs)　and　nanoparticles　(NPs)　onto　poly(heptazine　imide)　(PHI)　via　the　in-plane　Ru-N-4　coordination　and　interfacial　Ru-N　bonds,　respectively.　This　catalyst　shows　an　unsurpassed　CO　production　(32.8　mu　mol　h(-1)),　a　record-high　apparent　quantum　efficiency　(0.26%)　beyond　800　nm,　and　the　formation　of　the　valuable　H2O2.　Ru　SAs　tune　PHI＇s　electronic　structure　to　promote　in-plane　charge　transfer　to　Ru　NPs,　forming　a　built-in　electron　field　at　the　interface,　which　directs　electron-hole　separation　and　rushes　excited　electron　movement　from　Ru-PHI　to　Ru　NPs.　Simultaneously,　Ru　SAs　introduce　an　impurity　level　in　PHI　to　endow　long-wavelength　photoabsorption,　while　Ru　NPs　strengthen　CO2　adsorption/activation　and　expedite　CO　desorption.　These　effects　of　Ru　species　together　effectively　ensure　CO2-to-CO　conversion.　The　CO2　reduction　on　the　catalyst　is　revealed　to　follow　the　pathway　CO2　-＞　*CO2　-＞　*COOH　-＞　*CO　-＞　CO,　based　on　the　intermediates　identified　by　in　situ　diffuse　reflectance　infrared　Fourier　transform　spectroscopy　and　further　supported　by　density　functional　theory　calculations.