This research aims to synthesize and characterize the CO2 adsor+bent from waste tire (WT) as a precursor to produce porous carbon adsorbent material using a combination of thermal (pyrolysis, 600–700 °C) and chemical (H3PO4 and KOH) methods. The derived fine black powder was impregnated by 10–50 wt% polyethyleneimine (PEI) to produce porous carbon material (PEI-PCM) for evaluation of the performance of CO2 adsorption under TGA (micro-scale system). To observe the PEI loading and relevant CO2 capture selectivity characteristics, X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) method, and Fourier transform infrared spectrometry (FT-IR) were carried out. The XRD pattern showed the main phase of amorphous carbon, graphite, and some impurities (ZnS). Type II adsorption isotherm is related with reducing of the specific surface area and pore volume from 78 m2·g−1 to 25.26 m2·g−1, 0.45 cm3·g−1 to 0.23 cm3·g−1, respectively. The FT-IR spectra indicated the bending of primary and secondary amine which belonged to PEI molecule. It can be concluded that PEI-PCM properties such as, pore-size distribution, pore volume and surface functional groups supported CO2 adsorption capability following surface structure modification. The 50 wt% PEI-PCM-P showed good adsorption capacity of 53.81 mg·g−1 at temperatures of 75 °C. As a result, the PEI-PCM was successfully developed for CO2 absorption application. This work can help mitigating the challenge of disposal of WT and realization of the bio-circular-green economy (BCG model).