An increase of global population and consequent cause of environmental concerns, significant efforts have been made to reducing the use of fossil-based precursors and chemicals. The sustainable bio-benzoxazine resins were prepared using thymolphthalein and different amines systems such as aliphatic amines [butylamine (ba), hexylamine (ha), 2-ethylhexylamine (eha), dodecylamine (dda), octadecylamine (oda)), aryl amines (aniline (a), 4-fluoroaniline (fa), 3-trifluoromethylaniline (tfma)], and miscellaneous amines [cyclohexyamine (cha), allylamine (aa) and furfurylamine (ffa)] with paraformaldehyde through Mannich condensation. The molecular structure of corresponding benzoxazines was analysed using FTIR and 1H NMR spectroscopic techniques. Superhydrophobic cotton cloth was prepared using aliphatic amine based benzoxazine coating. The reinforcements bio-silica from bamboo ash and graphitic carbon nitride (GCN) from melamine precursors were separately prepared and functionalized under appropriate experimental conditions, which are used as reinforcement for the development of polybenzoxazine composites. Thermal stability, morphology and hydrophobicity of cardanol functionalized-GCN and GPTMS functionalized bio-silica reinforced polybenzoxazine composites were studied using TGA, FESEM and goniometer respectively. The poly(THP-oda) coated cotton fabric possesses the value of highest water contact angle of 154°. Further the poly(THP-oda) coated cotton fabric was tested for its efficiency towards oil-water separation. The value of dielectric constant of 15 wt% of bamboo ash silica reinforced poly(THP-ffa) and 15 wt% of C-GCN reinforced poly(THP-tfma) are 1.9 and 7.9 respectively.