The work presented here reports the greener synthesis of polyurea (GPUa) via in-situ solvent-free precipitation polymerization of toluene diisocyanate (TDI) (used as monomer) and water. The divalent manganese [Mn(II)] ions were incorporated into GPUa to form Mn(II)-GPUa to enhance its applicability. The structure of GPUa and Mn(II)-GPUa was validated by Fourier-transform infrared and proton nuclear magnetic resonance spectral techniques. The morphology along with the elemental analysis of GPUa and Mn(II)-GPUa was assessed by X-ray diffraction analysis and field emission scanning electron microscopy along with energy-dispersive X-ray spectroscopy. Thermal degradation behavior and stability of GPUa and Mn(II)-GPUa were investigated by thermo-gravimetric, differential thermal, differential scanning calorimetry, and integral procedure decomposition temperature analysis. Furthermore, the batch adsorption method was used to examine the adsorption behavior of Mn(II)-GPUa. The study's results indicated that Mn(II)-GPUa might be used as an eco-friendly, thermally stable material and adsorbent, making it suitable as an effective dye adsorbent for wastewater treatment. The current work is aligned with Green chemistry principles (Principles 1,2,3,4,5,6,8,and 12).