Abstract: Coal cinder is an abundant by-product due to the extensive consumption of coal for industrial production and daily life. Making full use of the cinder will be conducive to the low-carbon economy. Here, inspired by the burning of coal, a new method for construction the silica-based composite porous material (SiO2-CPM) was developed through combusting a siloxane-modified anthracite coal gel (CSiO2 gel). In this process, the combustion product was directly converted into porous material, with the calorific value of the coal remained nearly unchanged (~98% original calorific value retained), demonstrating the viability of this method in energy-efficient applications. The SiO2-CPM exhibited an ultra-low thermal conductivity (0.036 W/m·k at room temperature), outperforming conventional insulation materials (e.g., cotton ~0.05 W/m·k). Besides, it showed an improved mechanical strength (fracture stress 41.8 KPa) compared with the powder state of coal cinder. Experimental results demonstrated that the amount of siloxane, structure-directing agent and the acid environment were critical for the mechanical improvement. The SiO2-CPM showed a good dimensional stability against thermal expansion, and also displayed excellent thermal insulation and fire resistance even at 900°C. Meanwhile, the SiO2-CPM with complex geometry could be easily obtained by this method due to the good shaping ability of the CSiO2 gel. Compared to conventional methods like sol-gel or freeze-drying, this approach for fabricating SiO2-CPM is simpler, cost-effective, and allows direct utilization of coal cinder post-combustion.