This study presents a new series of amine-functionalized biochar derived from desiccated coconut waste (amine-biochar@DCW) as potential CO2 adsorbents. The CO2 adsorption experiment revealed that TETA-biochar@DCW had the highest adsorption capacity of 61.78 mg/g. Prior to the experimental studies, Density Functional Theory (DFT) was conducted at B3LYP/6-31G (d,p) to evaluate the energy band gap, global chemical reactivity descriptors (GCRD), and molecular electrostatic potentials (MEP) to compare the experimental findings. The results from the simulated data indicate that TETA-biochar@DCW has the lowest HOMO-LUMO gap at 2.7890 eV before adsorption, and it increases after CO2 adsorption occurs. The 3D plots from MEP also show that TETA-biochar@DCW is a reactive adsorbent for CO2 gases. Overall, the theoretical and experimental results of the amine-biochar@DCW suggest its potential as a promising and cost-effective adsorbent for CO2 capture.