Achieving excellent microwave absorption performance in ultralight Ti3C2T MXene with M−O bonds (M = Fe, Co, Ni) as surface terminating groups

• Novel MXenes with M−O bonds (M−Ti 3 C 2 T x , M = Fe, Co, Ni) as partial surface terminating groups were synthesized successfully for the first time. • First principles calculations revealed the effect of M−O bonds on polarization and conductive losses in M−Ti 3 C 2 T x . • M−Ti 3 C 2 T x achieved an excellent EAB of 4.90 GHz (1.63 mm) at low filling ratio of 2 wt%. • The enhanced microwave absorption performances originated from the synergetic optimization of dielectric and magnetic properties by M−O bonds, especially dielectric property. Modulating surface terminating groups has been recognized as an effective approach for regulating the electrical properties of MXene. Nevertheless, achieving the simultaneous majorization of electrical and magnetic properties of MXene through terminating groups modulation remains an essential challenge. Herein, we present an innovative series of M−Ti 3 C 2 T x (M = Fe, Co, Ni) with M−O bonds as partial terminating groups. First principles calculations are employed to investigate the impact of M−O bonds on electrical properties of M−Ti 3 C 2 T x . The M−O bonds introduce magnetic loss mechanisms while increasing polarization relaxation and conductivity, resulting in a synergistic optimization of dielectric and magnetic loss. Consequently, the Fe–Ti 3 C 2 T x achieves a favorable minimum reflection loss ( RL min ) of − 53.01 dB at 2.47 mm and an effective absorption bandwidth (EAB) of 4.20 GHz at 1.34 mm. The RL min of Co–Ti 3 C 2 T x reaches − 54.90 dB at 1.43 mm with an EAB of 3.94 GHz at 1.35 mm. The Ni–Ti 3 C 2 T x attains a RL min of − 47.66 dB and a remarkable EAB of 4.90 GHz at 1.58 mm and 1.63 mm, respectively. Notably, these excellent MA performances are accomplished with an exceptionally low filling ratio of merely 2 wt%, completely satisfying lightweight requirements of absorbers. This research presents a novel method for designing efficient absorbers with simultaneous optimized electromagnetic properties by terminating groups modulation.