The persistent increase in atmospheric CO₂ levels presents a dual challenge of environmental mitigation and sustainable energy generation. This study introduces a unified nano-engineered platform combining nanostructured metals, plasmonic nanoparticles, quantum dots, and defect-rich TiO₂ to drive selective CO₂ conversion into CO, CH₄, and CH₃OH. By leveraging synergistic nano-interfaces, this work integrates catalytic activity with optoelectronic functionality, enabling simultaneous energy harvesting and chemical transformation. Nanostructured metals provide tailored surface states for CO₂ adsorption, while plasmonic nanoparticles induce hot-electron injection, and quantum dots facilitate directional charge transfer. Defective TiO₂ layers introduce oxygen vacancies that localize charges and modulate reaction pathways. Comprehensive material characterization using TEM, XRD, XPS, PL, and UV–Vis spectroscopy confirms controlled interface formation, defect density, and optical enhancement. CO₂ conversion experiments under gas-phase and photo-assisted modes demonstrate tunable product selectivity via defect engineering and electrical bias application. The hybrid platform achieves enhanced Faradaic efficiency, turnover number, and operational stability compared to conventional systems. Mechanistic insights reveal that defect-plasmon-quantum dot interactions govern charge localization and transfer, providing a predictive framework for reaction steering. Integration with photovoltaic and optoelectronic modules showcases the feasibility of combined chemical and energy conversion, offering a pathway toward scalable, smart CO₂-to-fuel system. These findings provide a transformative approach to CO₂ utilization, highlighting the potential for decentralized renewable energy generation and sustainable fuel production. The methodology and insights reported herein establish a foundation for designing multi-functional catalytic systems with controllable reaction pathways and integrated energy recovery.