Porous graphitized carbons (PGCs), with the texture mimicking activated carbons while the framework resembling few-layer graphene, promise intriguing opportunities in versatile applications. Nonetheless, shortage of facile strategies to achieve high graphitization levels without compromising porosity remains a bottleneck. We demonstrate that various carbon precursors, including activated carbon, biomass, biochar, anthracite and synthetic polymer, can be converted to large-surface-area PGCs by joint treatment using both potassium hydroxide and a catalyst. In particular, using activated carbon as the precursor, BET surface areas exceeding 2000 m2/g can be readily achieved. Besides, joint treatment introduces mesoporosities to the products. We propose that molten potassium hydroxide can promote metal-catalyzed graphitization of carbon precursors, while preventing intensive graphene sheet stacking, forming thin graphitized flakes that construct highly porous structures. The PGCs can be used as moisture-resistant VOC adsorbents owing to their excellent hydrophobicity. The joint-treatment process can realize a scale-up fabrication of high-quality PGCs.