<p>The synthesis of functional polymers from carbon dioxide (CO₂) remains a central yet challenging goal in sustainable polymer chemistry. In this study, we present a novel strategy to produce polycarbosilanes containing intact lactone ring units from CO₂, butadiene and silanes. Key to this strategy is the preparation of functional dienes from CO₂ and butadiene, which are subsequently copolymerized with silanes via a photocatalytic step-growth hydrosilylation polymerization. The resulting CO₂/butadiene/silane terpolymers exhibit excellent thermal stability and high glass transition temperatures. The intact lactone ring units can undergo facile backbone editing via base-promoted hydrolysis. Notably, treatment of the functional polycarbosilanes with tetrabutylammonium fluoride led to significant polymer degradation to oligomers under mild conditions. This methodology establishes a versatile and sustainable platform for designing high-performance and degradable CO₂-derived polymers.</p>