We study the production of ultra-high-energy particles via the Bañados-Silk-West mechanism in the premerger phase of binary systems detected by LIGO-Virgo-KAGRA. By solving the geodesic equations for charged particles in magnetized Kerr spacetime with fields of $B\sim {10}^{12}–{10}^{14}\mathrm{G}$, we demonstrate that collisions near the horizon can achieve center-of-mass energies $E_{\mathrm{cm}}\sim {10}^{18}–{10}^{20}\mathrm{eV}$, placing them firmly in the ultra-high-energy cosmic-ray (UHECR) range. We systematically explore the parameter space of merger remnants, varying black hole mass ($M\sim 20–150M_{\odot }$, characteristic of the binary black hole population), dimensionless spin (${\chi }_f\sim 0.7–0.9$), magnetic field strength, and particle angular momenta. Our analysis reveals three distinct acceleration regimes: a gravity-dominated regime ($B<{10}^{12}\mathrm{G}$) with negligible magnetic enhancement, a transition regime (${10}^{12}\mathrm{G}\lesssim B\lesssim {10}^{13}\mathrm{G}$) where gravitational and magnetic effects compete, and a magnetic-dominated regime ($B>{10}^{13}\mathrm{G}$) where fields amplify collision energies by nearly an order of magnitude. For the 34 gravitational-wave events with high remnant spins (${\chi }_f>0.7$), we compute the maximum achievable energies, finding that systems with ${\chi }_f\gtrsim 0.85$ and $M\gtrsim 100M_{\odot }$ can reach $E_{\max }\sim {10}^{20}\mathrm{eV}$. Our results establish magnetized binary mergers, particularly black hole–neutron star systems and postmerger black hole remnants formed in binary neutron star coalescences, as promising sources of UHECRs and provide quantitative predictions linking gravitational-wave observables to particle acceleration efficiency.

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• Classical black holes
• Cosmic ray acceleration
• Gravitational wave sources