Ordered mesoporous carbons with semi-graphitized walls (OMCs-SGW) were successfully obtained by in situ silica-confined thermal decomposition of methane at low temperatures (800–1000 °C). This novel method, adopting ordered mesoporous silicas (OMSs) as hard templates, impregnating OMSs with small amounts of group VIII metal (Fe, Co, Ni) nitrates as catalysts, combining pore infiltration and carbonization/graphitization processes into a single step, provides an efficient way for the synthesis of OMCs-SGW. Methane, a special carbon precursor with small molecular size, is adopted because it allows complete penetration, and full carbon deposition inside the mesopores and is an easy graphitization process at low temperature assisted by catalysts. Two mesoporous silica materials, SBA-15 with hexagonal structure (p6m) and KIT-6 with cubic bicontinuous structure (Ia3d), were used as hard templates. SAXS patterns and TEM results show that the obtained carbon materials are faithfully replicated from the mesostructures of silica templates. Their pore walls are semi-graphitized and little structural shrinkage and negligible micropores are observed. The textural, structural properties and degree of graphitization of the OMCs-SGW can be conveniently tuned by controlling the temperature, namely, higher temperatures (e.g. 1000 °C) lead to products with more ordered and graphitized frameworks, but lower surface areas and pore volumes (about 390 m2/g and 0.45 cm3/g), while lower temperature (800 °C) results in products with less ordered and graphitized structures, but very high surface areas and pore volumes (up to 1200 m2/g and 2.08 cm3/g). OMCs-SGW can also be synthesized without catalysts. They have higher surface areas and pore volumes but much lower graphitized structures than the counterparts synthesized with catalysts. These OMCs-SGW show good hydrogen uptake capabilities (up to ~2 wt% at 10 bar and 77 K).