Tunable synthesis of tailored high-energy-density fuels from coal-based fluorene

High-energy-density (HED) fuels are crucial for volume-limited hypersonic propulsion systems, yet their petroleum-dependent production poses energy security challenges, especially for nations like China with scarce oil reserves. While coal-derived naphthalenes and anthracenes have been investigated for HED fuel production, their extended π-conjugation restrict tunability of key fuel properties. Here, we propose a molecular engineering strategy using coal-based fluorene as a versatile platform for the tunable synthesis of tailored HED fuels. The ring-increasing condensation of fluorene with benzaldehyde over CaO, coupled with hydrogenation, yields a tetracyclic fuel with higher energy density than JP-10, rendering it a prime candidate for high thrust application. The long-alkyl substitution strategy involving catalytic butylation and hydrogenation generates a butyl-tricyclic fuel with a balanced profile of energy density and flowability, demonstrating potential for cold-climate operations. Additionally, AlCl 3 -catalyzed skeletal rearrangement of hydrogenated fluorene produces trimethyladamantane with exceptional thermal stability, which may mitigate thermal management issues in hypersonic flight. Life-cycle assessment reveals that three fluorene-derived multicyclic alkanes show clear carbon-emission advantages over petroleum-based fuel JP-10. This study provides a strategic material solution for hypersonic aerospace applications, addressing critical performance demands while strengthening supply resilience through feedstock diversification.