Very thin microporous organic networks were formed on the surface of Fe3O4 nanospheres by Sonogashira coupling of tetra(4-ethynylphenyl)methane and 1,4-diiodobenzene. The thickness was controlled by screening the number of building blocks. Through carbonization, Fe3O4@C composites were prepared. The Fe3O4@C composites with 4-6 nm carbon thickness showed promising reversible discharge capacities of up to 807 mA h g(-1) and enhanced electrochemical stability.