Hydrothermal dechlorination has been widely studied for recycling end-of-life polyvinyl chloride while the impact of embedded metal additives, a major component of many waste PVC products, has rarely been reported. In this study, hydrothermal treatment of used polyvinyl chloride pipe was carried out at a temperature range between 220 and 280 °C to understand the role of metal additives in the dechlorination process. The potential application of chlorine-free hydrochar as the precursor to prepare CO2 sorbents via chemical activation was also evaluated. The results demonstrated that the well-distributed calcium carbonate in the polyvinyl chloride matrix, acting as an in-situ neutralization agent, could accelerate the dechlorination of PVC, over 98.4% of chlorine was removed at 260 °C or higher. Using the hydrochar prepared at 260 °C as a single precursor, a series of activated carbons were successfully prepared via a facile chemical activation process. Those hydrochar-derived carbons have a microporous dominant structure with high surface area and total pore volume reaching up to 1927 m2 gâ1 and 0.85 cm3 gâ1, which showed great potential as CO2 sorbents. Tested at 25 °C, the microporous carbons exhibited both remarkable CO2 adsorption capacities of 1.60 mmol gâ1 and 4.05 mmol gâ1 at 100 kPa and high CO2/N2 selectivity of 42 at 15 kPa CO2. Advanced characterization demonstrated that the excellent CO2 adsorption performance originated from a unique combination of ultra-microporosity and surface chemistry. This work provides an effective and sustainable strategy to recycle hard-to-handle chlorinated plastic waste and reduce carbon emissions.