• Deep eutectic gels with tunable hydrogen bond (HB) density were synthesized by varying the ChCl:EG molar ratio, enabling systematic study of HB effects on EMW absorption.
• The optimal gel (G22-CE2.4) achieved an effective absorption bandwidth of 8.50 GHz at 2.54 mm thickness, attributed to enhanced conduction loss and impedance matching from optimal HB content.
• This work is the first to elucidate the role of hydrogen bonds in dielectric loss, providing a new mechanism for designing high-performance EMW absorbers.
• The findings offer a rational strategy for optimizing supramolecular polymer absorbers by controlling intermolecular interactions, with potential applications in electromagnetic pollution mitigation.