The development of functional materials with better flame-retardant and thermal insulation properties has attracted considerable attention for energy storage applications in modern society. Here, we describe a facile approach for the preparation of conjugated microporous polymer hollow spheres (CMP-HSs) by using SiO2 nanoparticles as a template via the Sonogashira-Hagihara cross-coupling reaction. The assynthesized CMP-HSs have good thermal stability with a thermal decomposition temperature of up to 281 degrees C, high porosity (the BET specific surface area is measured to be approximately 666 m(2) g(-1)) along with lipophilic and hydrophobic characteristics. To further improve their flame retardancy, CMP-HSs were treated with dimethyl phosphonate (DMMP) though an immersion method to prepare the CMPHSs composite (CMP-HSs-DMMP) flame-retardants. By introducing CMP-HSs-DMMP into the epoxy resin (EP) matrix, the as-prepared EP composites showed excellent flame-retardant properties, e.g., the peak heat release rate (pHRR) and total heat release (THR) value of EP composites containing only 0.2% CMP-HSs-DMMP flame-retardant were 650.9 kW m(-2) and 79.4 MJ m(-2) respectively, in the range of 0 degrees C - 650 degrees C, which are 19.6 +/- 2% and 19.1 +/- 5% lower than that of pure EP within the same temperature range. Considering the significant enhancement of its flame retardancy with only a slight dosage of CMPHSs-DMMP, such CMP hollow sphere-based flame-retardant composites may have great potential as functional bulk materials or coatings in a variety of fireproofing applications. (C) 2020 Elsevier Inc. All rights reserved.