Aqueous phase-transfer catalysis enables selective iodination of PVC under mild and sustainable conditions. Subsequent reaction with a DBU-based CO₂-binding amine (CO₂BAM) achieves efficient S_N2 substitution at CH–X centers, improving CO₂ incorporation fourfold relative to previous CO₂BAL strategies. The polymer remains fully soluble, demonstrating a greener, safer, and effective approach to PVC structural modification.