LAUSR

Porous boron carbon nitride (BCN) is one of the exciting systems with unique electrochemical and adsorption properties. However, the synthesis of low‐cost and porous BCN with tunable porosity is challenging, limiting its full potential in a variety of applications. Herein, the preparation of well‐defined mesoporous boron carbon nitride (MBCN) with high specific surface area, tunable pores, and nitrogen contents is demonstrated through a simple integration of chemical polymerization of readily available sucrose and borane ammonia complex (BAC) through the nano‐hard‐templating approach. The bimodal pores are introduced in MBCN by controlling the self‐organization of BAC and sucrose molecules within the nanochannels of the template. It is found that the optimized sample shows a high specific capacitance (296 F g−1 at 0.5 A g−1), large specific capacity for sodium‐ion battery (349 mAg h−1 at 50 mAh g−1), and excellent CO2 adsorption capacity (27.14 mmol g−1 at 30 bar). Density functional theory calculations demonstrate that different adsorption sites (BC, BN, CN, and CC) and the large specific surface area strongly support the high adsorption capacity. This finding offers an innovative breakthrough in the design and development of MBCN nanostructures for energy storage and carbon capture applications.