A chemical-free method is developed to convert cotton fabric into reactive mesoporous carbon via optimized carbonization and oxidation processes. The processed carbon serves as both catalyst support and reactant which controls the nucleation/growth of Ag nanoparticles. The particle size is successfully controlled below 5 nm with mono-dispersion on carbon support. Various characterization techniques including scanning/transmission electron microscopies, N-2 adsorption-desorption, X-ray diffraction, X-ray photoelectron spectrum are used to study the evolution of carbon support microstructure and surface composition during thermal oxidation as well as the in-situ reaction between carbon support and Ag precursor during hybridization. These Ag/carbon catalysts, with well-controlled Ag nanoparticle size and excellent dispersion, out-perform other existing catalysts reported from literature in terms of activity and stability. The unique property of these catalysts promises potential applications in other chemical reactions besides the demonstrated capability in nitroaromatics reduction. Moreover, this green technology of processing biomass into effective catalyst support provides a great platform to design metal/carbon hybrid catalysts from wider biomass resources and target to broader catalytic reactions. (C) 2015 Elsevier B.V. All rights reserved.