Ordered mesoporous carbon C-FDU-18s with tunable pore sizes of 12−33 nm and pore wall thicknesses of 5−11 nm were synthesized by using poly(ethylene oxide)-block-poly(styrene) (PEO-b-PS) diblock copolymers with various PS chain lengths as templates and through the evaporation induced self-assembly process. The obtained C-FDU-18 carbons possess face-centered cubic mesostructure with Fm3m symmetry, large cell parameters varying from 32 to 54 nm, high Brunauer–Emmett–Teller surface area up to 1000 m2 g−1 and large pore volume of about 0.7 cm3 g−1. By oxidative treatment of HNO3 and H2O2 mixed solution, numerous hydrophilic groups were created in the mesopore channels without destroying the ordered mesostructure of the C-FDU-18. Through the in situ reduction of Ag+, Ag nanoparticles (9.7 nm) were successfully introduced into the large mesopores, resulting in functional mesoporous carbons Ag–C-FDU-18 with stably trapped Ag nanoparticles. Similarly, by reduction of Fe3+ ions in the large mesopores, superparamagnetic Fe–C-FDU-18 with incorporated magnetic nanoparticles (6.2 nm) and fast magnetic response was synthesized. These functional large-pore mesoporous carbons have high potential for application in various fields such as catalysis, chemical sensing, and magnetic separation and enrichment.