Hydrophobic and photocatalytic cotton fabric was created through a simple dip-coating combining with methyltrimethoxysilane (MTMS), tetraethyl orthosilicate (TEOS) and graphitic carbon nitride (g-C₃N₄). The hybrid silica g-C₃N₄ network exhibits hierarchical roughness, high thermal stability, and visible-light activity, as confirmed by XRD, SEM-EDX, FTIR, and TGA. The coated fabrics displayed robust water repellency with a contact angle of 133 ± 3° and achieved > 88% degradation of methylene blue under visible light, following pseudo-first-order kinetics (k = 0.00995 min−1). The synergy of MTMS+TEOS+g-C₃N₄ enabled durable self-cleaning behaviour and resistance to liquid penetration. This scalable, fluorine-free route demonstrates a sustainable pathway for multifunctional fabric, with applications spanning outdoor protective fabrics, environmental remediation and advanced military clothing.