A macroporous silicon micromonolith containing ca. 40,000 regular channels of 3.3 ¿m in diameter per square millimeter has been successfully functionalized with an Au/TiO2 catalyst for CO preferential oxidation (CO-PrOx) in the presence of hydrogen. The functionalization of the silicon microchannels has been accomplished by growing a SiO2 layer on the channel walls, followed by exchange with a titanium alkoxyde precursor and decomposition into TiO2 and, finally, by anchoring carbosilanethiol dendron protected pre-formed Au nanoparticles. Catalytically active centers at the Au-TiO2 interface have been obtained by thermal activation. With this method, an excellent homogeneity and adherence of the catalytic layer over the microchannels of the macroporous silicon micromonolith has been obtained, which has been tested for CO-PrOx at 363-433 K and ¿=2 under H2/CO=0-20 (molar). The macroporous silicon micromonolith converts ca. 3 NmL of CO per minute and mL of microreactor at 433 K under H2/CO=20, suggesting that it could be particularly effective for hydrogen purification in lowtemperature microfuel cells for portable applications.