The excessive exploitation of fossil fuels has led to escalating energy shortages and CO₂ emissions, posing severe threats to sustainable development. Against the backdrop of carbon neutrality goals, green CO₂ conversion technologies have garnered significant attention. Among them, photocatalytic CO₂ reduction offers a sustainable route to convert CO₂ into value-added solar fuels using abundant sunlight. However, current systems face critical challenges such as rapid recombination of photogenerated charge carriers and insufficient redox capability, which limit overall efficiency. To address these bottlenecks: (1) A SnO₂/CDs Ohmic heterojunction was constructed by incorporating carbon quantum dots (CDs) into SnO₂ nanofibers. Under illumination, photogenerated electrons in SnO₂ are driven to the CDs surface by band bending and the built-in electric field, where they are synergistically excited with the intrinsic free electrons of CDs via localized surface plasmon resonance (LSPR), forming a stable carrier cycling mechanism that prolongs carrier lifetime. Enhanced light absorption and efficient CO₂ chemisorption by CDs further boost the photocatalytic performance. (2) An In₂O₃/Nb₂O₅ S-scheme heterojunction was fabricated via one-step electrospinning, achieving tight interfacial contact and ultrafast charge transfer (<10 ps). The photogenerated electrons and holes accumulate in the conduction band of Nb₂O₅ and the valence band of In₂O₃, respectively, benefiting from extended carrier lifetimes and strong redox potential. Moreover, the strong CO₂ adsorption and activation capability of Nb₂O₅ contributes to the improved catalytic activity. (3) To further overcome charge recombination and reaction kinetics mismatch, a spatially engineered Nb₂C/Nb₂O₅/ZnO ternary heterostructure is developed by anchoring ZnO quantum dots (QDs) onto Nb₂O5 nanorods grown in situ from Nb₂C MXene. This architecture integrates an Nb₂O₅/ZnO S-scheme heterojunction and an Nb₂C/Nb₂O₅ Schottky junction, both sharing Nb₂O₅ as a central mediator, thereby establishing bidirectional interfacial electric fields (IEFs) that direct photogenerated electrons toward ZnO and holes toward Nb₂C. This spatial charge separation effectively suppresses Coulombic recombination and prolongs carrier lifetimes. Additionally, the intrinsic photothermal effect of Nb₂C MXene enhances CO₂ chemisorption and activation at defective ZnO QDs. These synergistic effects collectively enable high-efficiency CO₂ photoreduction without molecular cocatalysts or sacrificial agents, providing a mechanistically distinct and scalable approach for artificial photosynthesis.