Confining Fe₃O₄ into nanoporous carbon frameworks has been achieved through self-assembly and the use of a subsequent syn-carbonization strategy, where Fe₃O₄ and carbon frameworks are generated simultaneously and Fe₃O₄ particles are confined into porous carbon frameworks (Fe₃O₄@C). Both the composition and microstructure have a significant effect on the electrochemical performances. In comparison with bulk Fe₃O₄, Fe₃O₄@C-2 with optimal void pore volume and oxide content shows a significant enhancement in both cycling stability and high-rate capacity. The reversible capacity of Fe₃O₄@C-2 is retained at 932 mA h g⁻¹ after 100 cycles compared to only 410 mA h g⁻¹ for bulk Fe₃O₄. The capacity of Fe₃O₄@C-2 at the current density of 2 A g⁻¹ has been significantly improved to 478 mA h g⁻¹ from only 26 mA h g⁻¹ for bulk Fe₃O₄. The considerable enhancement of both the cyclability and high-rate capability can be attributed to the synergic effect of nanoconfinement as well as the optimized composition and microstructure: the good dispersion of oxide particles, and the efficient volume change alleviation during the discharge–charge process.