Constructing heterojunctions with rich porosity and unique microstructures is the main way to obtain efficient adsorption and photocatalysis. A ternary composite of Co3O4–TiO2 supported in N-doped magnetic 3D porous microspheres (Co3O4–TiO2/N-MCMs) was successfully constructed with hierarchical pore structures, large specific surface areas, and abundant active sites. The Co3O4–TiO2/N-MCMs possessed excellent adsorption and solar degradation capabilities for representative azo dye (methyl orange, MO) and triphenylmethane dye (rhodamine B, RhB), and the total removal rate of the two dyes with different initial concentration reached up to 99.0% and 99.2% within 2 h, respectively. MO and RhB were rapidly adsorbed and enrichment into Co3O4–TiO2/N-MCMs via pore filling, and then degraded by the nucleophilic reagents (•O– 2 and •OH). Characterizations and theoretical calculations demonstrated that Co3O4–TiO2/N-MCMs contained a sufficient amount of p-n type heterojunctions between Co3O4 and TiO2, which could effectively promote spatial separation of photogenerated e--h+ pairs to improve degradation ability and reduce band gap to extend visible-light absorption. Moreover, N-doping could further transfer photogenerated electrons from heterojunctions to reaction areas to effectively prolong the lifetime of photogenerated electrons. The LC-MS results showed that MO and RhB can be mineralized into H2O and CO2 without generating any secondary pollution. Furthermore, Co3O4–TiO2/N-MCMs exhibited excellent magnetic separation capability and reusability. This study designed a novel photocatalyst for highly efficient removal of organic dyes via “One stone with two birds” strategy of synergistic adsorption-photocatalysis, which could simplify the treating process and exhibit a highly promising in practical applications.