Carbon materials with ordered mesoporous and/or well-defined hollow nanostructures are promising candidates for adsorbates, optical devices, nanoreactors, electrochemical supercapacitors, and storage materials. [1][2][3][4] These nanostructured carbons are commonly fabricated by using templating procedures using silica-based molds, which involve coverage or filling of the surfaces of the molds with carbon sources followed by carbonization under inert conditions and subsequent removal of the molds using chemical etching. To date, various carbon sources have been employed to control the level of graphitization of carbon networks for the purpose of adjusting conductivity, stability, and porosity in order to satisfy conditions for desired applications as well as to simplify the preparation procedure. [2,4] These nanostructured carbons also exhibit potential abilities as efficient catalysts and electrocatalysts for various reactions when they are used in combination with metal nanoparticles, that is, carbon-metal nanocomposites. [1c,3b,d,4b] Although some studies have reported high catalytic functions of such composites, [1c,3d] effective control of metal size and dispersion in such composites as catalysts is yet to be established. When carbon-metal catalyst composites are fabricated by the reported methods, additional workup procedures, such as pretreatment of the silica molds with metal particles and post-loading of them on the thus-obtained carbon materials, are indispensable. Therefore, a more convenient approach for the preparation of such composites will be appreciated.Here, we report a simple and unique method for obtaining a carbon-metal catalyst composite, that is, Pt nanoparticles incorporated in microporous hollow carbon nanospheres (nPt@hC), through the photocatalytic reaction of TiO 2 nanoparticles in deaerated aqueous media. In this method, TiO 2 nanoparticles not only act as molds of hollow carbon but also induce simultaneous deposition of Pt nanoparticles and phenolic polymers by photocatalytic reduction and oxidation of a platinum(IV) precursor and phenol, respectively. Although photodeposition of metal nanoparticles on photocatalytic materials is a well-known phenomenon [5] and has been applied to fabricate composites of metal/semiconductor nanoparticles in some studies, [6] this is the first report of the synthesis of nanocomposites using both reduction and oxidation abilities of photocatalysis. In addition, as an example of the use of nPt@hC, we also show its efficient catalytic functions for liquid-phase hydrogenation of olefins. Photoirradiation was performed in an air-free closed gas circulation system with a Pyrex reaction cell. The TiO 2 photocatalyst used was commercial anatase TiO 2 powder supplied by Ishihara Sangyo (ST-21). A suspension containing the TiO 2 powder, phenol, and a small portion of hexachloroplatinic acid (H 2 PtCl 6 , containing Pt atoms corresponding to 0.3 wt % for TiO 2 ) was photoirradiated under Ar (30 kPa) with a highpressure Hg lamp through a Pyrex water jack...