Bombyx　mori　silk,　a　natural　nitrogen-rich　biopolymer　protein,　is　earth-abundant　and　sustainable.　In　this　study,　nitrogen-doped　carbon　quantum　dots　(N-CQDs)　derived　from　Bombyx　mori　silk　fibroin　are　immobilized　onto　TiO2　nanotube　arrays　(TiO2　NTAs)　by　a　facile　hydrothermal　process.　The　resulting　N-CQDs　decorated　TiO2　NTA　heterostructures　(N-CQDs@TiO2　NTAs)　display　a　maximum　incident　photon-to-electron　conversion　efficiency　(IPCE)　of　32.5%　under　450　nm　monochromatic　light　in　neutral　solution.　Compared　with　pristine　TiO2　NTAs,　the　N-CQDs-decorated　TiO2　NTAs　demonstrate　significantly　improved　photocatalytic　efficiency　during　the　degradation　of　organic　contaminants.　Furthermore,　the　constructed　heterostructures　are　used　to　split　water　to　investigate　their　photocatalytic　promise,　yielding　the　maximum　H-2　and　O-2　production　rates　of　30.12　and　14.96　mu　mol　cm(-2)　h(-1),　respectively.　Optimizing　the　N-CQD　coating　is　found　to　effectively　tune　the　bandgap　and　up　conversion　capability　of　the　heterostructures,　enabling　unique　photon　harvest　and　boosting　photocatalytic　activity.　This　study　provides　a　proof　of　concept　that　nonmetal,　abundant,　and　sustainable　materials　can　be　exploited　to　enhance　the　photocatalytic　capability　of　TiO2,　imparting　a　variety　of　unique　applications　such　as　water　purification　and　chemical　fuel　production.