Manipulating Terminal Bonds of Ti₃C₂T_x MXene for Highly Efficient Microwave Absorption and Photothermal Conversion

MXenes have been widely investigated as microwave absorption (MA) materials because of their unique properties. This study introduces a terminal bond manipulation strategy to enhance charge transfer and polarization in Ti₃C₂T_x, optimizing its MA performance. The strategy uses molten salt etching to create Ti₃C₂T_x MXenes with F, Cl, or Br as terminal groups. Among these, Ti₃C₂Cl_x demonstrates the best MA performance, with a minimum reflection loss of −55.18 dB at an absorber thickness of 1.63 mm and an effective absorption bandwidth of 5.36 GHz at an absorber thickness of 1.52 mm, respectively. Density functional theory reveals directional charge transfer from Ti to T (T = F, Cl, or Br) and moderate dipole polarization, which optimize impedance matching, polarization loss, and conductive loss for enhanced MA performance. Additionally, Ti₃C₂Cl_x improves the mechanical and thermal properties of polydimethylsiloxane (PDMS). Typically, Ti₃C₂Cl_x/PDMS composite with 1.2 wt% Ti₃C₂Cl_x shows 230% increase in tensile strength, 224% improvement in elongation, and 170% rise in thermal conductivity compared to pure PDMS. Moreover, the composite also exhibits excellent photothermal conversion performance, reaching 60°C under simulated sunlight irradiation of 100 mW·cm⁻². This strategy offers a pathway for developing next-generation materials with multifunctional properties for intelligent systems.