This study highlights hydrophobic tail engineering in gemini surfactants as an effective molecular strategy to regulate the synthesis, colloidal stability, and catalytic characteristic of silver nanoparticles (AgNPs). Three hydrophobic gemini surfactants with systematically varied alkyl chain lengths of 8 carbons (GSO), 12 carbons (GSD), and 16 carbons (GSH) were employed to direct AgNP nucleation and growth through surfactant-mediated interfacial interactions. Increasing hydrophobic tail length significantly enhanced micellization behavior, surface adsorption, and coordination with Ag. ions, thereby enabling precise control over nanoparticle size, dispersion, and surface charge. Among the investigated systems, GSH has lower CMC of 0.562 mM and highest adsorption energy (.. 73.7 kJ·mol.¹), providing a uniformly dispersed AgNPs with diameter of 12.7 ± 3.9 nm and a high positive zeta potential (+25.6 ± 6.6 mV). To address nanoparticle recovery and reuse challenges, a reusable catalytic membrane was fabricated via in-situ photochemical synthesis AgNPs on sponge scaffold. The resulting sponge@AgNPs membrane was integrated into a flow-through catalytic column for efficient of methylene blue (MB) reduction to leucomethylene blue (LMB) over 15 consecutive cycles. Structural integrity and homogeneous AgNP distribution were confirmed by SEM, EDX, and XRD analyses. In addition, AgNPs stabilized with GSD exhibited strong antimicrobial activity, outperforming several benchmark agents. Overall, this work establishes a facile, scalable, and environmentally benign strategy that combines surfactant molecular design with column engineering, demonstrating versatile chances for sustainable catalysis and water purification applications.