Lithium–sulfur battery is one of the most promising energy storage systems for its high specific capacity. However, commercial development of lithium–sulfur batteries is severely hindered by the cathode host materials. To tackle this issue, we synthesized a new host material, high surface area, three-dimensional (3D) diamond-cage porous polymer frameworks PPN-13, to construct sulfur electrode by impregnating sulfur into its nano-pores. The PPN-13-S cathode deliveries a specific discharge capacity up to 606.4 mA h/g over 100 cycles at 0.1 C with a high coulombic efficiency. It demonstrates that the 3D porous structure PPN-13 as host material shows the high performance and a remarkable positive effect on the capacity retention as cathode materials in lithium–sulfur batteries. Due to the unique features of the material, our research provides a new type of materials for tailoring cathode materials in lithium–sulfur batteries.