Self-templated synthesis of boron-doped porous carbon by chemical interaction of 2LiBH4·CO2 with CO2

•A new compound of 2LiBH4·CO2 is synthesized for the first time.•A self-template method is developed to synthesize heteroatom–doped carbon from CO2.•Self-template mechanism is revealed based on new reactions of CO2 with 2LiBH4·CO2.•A capacity of 890 mAh/g of BPC is retained after 1200 cycles at 1.0 A/g.