Feedstock-Driven Design of CO2 Sorbents via Chemical Upcycling of Plastics and Elastomers.

Plastic and elastomer wastes are abundant, carbon-rich feedstocks. At the same time, carbon capture requires sorbents that perform under realistic temperatures, humidity, dilute CO2, and repeated regeneration. This review surveys feedstock-driven chemical upcycling routes that transform waste polymers into CO2 sorbents, while treating carbonization-derived physisorbents as a comparative benchmark and pragmatic fallback for chemically intractable or highly heterogeneous feedstocks. We frame "waste-to-sorbent" conversion as a feedstock-driven design problem in which inherited constitutional chemistry, network and morphology, formulation, and acquired chemistry-collectively termed chemical memory-govern feasible transformations and capture performance. We organize the literature by major feedstocks-PET, PVC, polystyrene, rubbers/tires, polyolefins, and mixed plastics-and compare physisorption- and chemisorption-dominant architectures with emphasis on binding-site accessibility, transport limits, humidity effects, impurity tolerance, oxidative stability, and regeneration windows. Because cross-study comparison is often hindered by inconsistent testing conditions and incomplete characterization of both starting feedstocks and resulting sorbents, we propose a mechanism-aware benchmarking framework and minimum reporting protocol centered on feedstock descriptors, application-relevant CO2 partial pressures, working capacity, accessible-site metrics (e.g., effective nitrogen/amine efficiency), ultramicropore descriptors, and durability under humid/impure cycling. These guidelines connect feedstock chemistry to deployable sorbent design and accelerate translation beyond headline capacities.