In　the　quest　to　enhance　photocatalytic　performance,　structural　regulation　and　interface　engineering　stand　out　as　effective　strategies　for　amplifying　active　sites　and　fostering　the　separation　of　photogenerated　electron-hole　pairs.　In　this　study,　a　pioneering　approach　was　employed,　utilizing　a　straightforward　two-step　calcination　method　to　prepare　a　novel　photocatalyst:　porous　graphite　carbon　nitride　(g-C3N4,　CN)　nanosheets　(NS)　loaded　with　mesoporous　cerium　oxide　(CeO2/CNNS).　The　distinctive　architecture　of　CeO2/CNNS　not　only　elevates　the　specific　surface　area　and　catalytic　active　sites　but　also　facilitates　efficient　mass　transfer.　Experimental　results　and　density　functional　theory　(DFT)　calculations　corroborate　the　existence　of　an　internal　electric　field　(IEF)　within　the　Zscheme　heterojunction　formed　by　uniformly　dispersed　CeO2　and　CNNS.　This　IEF　proves　pivotal　in　promoting　charge　separation　and　migration,　thereby　maintaining　robust　redox　capabilities.　Under　visible　light　irradiation,　CeO2/CNNS　demonstrates　an　impressive　4.2-fold　increase　in　the　hydrogen　production　rate　compared　to　bulk　gC3N4　(BCN),　coupled　with　a　48.5%　boost　in　the　photocatalytic　degradation　rate　constant　(k)　of　tetracycline　(TC).　This　study　not　only　unveils　the　innovative　design　of　CeO2/CNNS　but　also　paves　the　way　for　a　fresh　perspective　on　the　design　and　preparation　of　multifunctional　photocatalysts.