We report a facile approach that can simultaneously control the morphology and surface chemistry of mesoporous materials from triblock copolymers. By doping phosphotungstic acid (PW), the self-assembled structures of polystyrene–poly(ethylene oxide)–polylactide (PS–PEO–PLA, SEL) triblock copolymer can be tuned. Besides core–shell cylinders and lamellae, disordered bicontinuous structures can be achieved in SEL/PW composites. After etching with NaOH, PLA domains and PW additive are removed simultaneously, giving mesoporous PS monoliths with controlled morphologies and PEO-coated pores. Also, we demonstrated that the prepared porous PS monoliths can be used as templates to fabricate inorganic nanostructures. This work provides new insight into the fabrication of functional mesoporous materials.