Chong Min Koo

Heterointerface engineering, which plays a pivotal role in developing advanced microwave‐absorbing materials, is employed to design zeolitic imidazolate framework (ZIF)–MXene nanocomposites. The ZIF–MXene composites are prepared by electrostatic self‐assembly of negatively charged titanium carbide MXene flakes and positively charged Co‐containing ZIF nanomaterials. This approach effectively creates abundant Mott–Schottky heterointerfaces exhibiting a robust built‐in electric field (BIEF) effect, as evidenced by experimental and theoretical analyses, leading to a notable attenuation of electromagnetic energy. Systematic manipulation of the BIEF‐exhibiting heterointerface, achieved through topological modulation of the ZIF, proficiently alters charge separation, facilitates electron migration, and ultimately enhances polarization relaxation loss, resulting in exceptional electromagnetic wave absorption performance (reflection loss RL min = −47.35 dB and effective absorption bandwidth f E = 6.32 GHz). The present study demonstrates an innovative model system for elucidating the interfacial polarization mechanisms and pioneers a novel approach to developing functional materials with electromagnetic characteristics through spatial charge engineering.

Surface plasmons in 2D materials such as graphene exhibit exceptional field confinement. However, the low electron density of majority of 2D materials, which are semiconductors or semimetals, has limited their plasmons to mid‐wave or long‐wave infrared regime. This study demonstrates that a 2D Ti 3 C 2 T x MXene with high electron density can not only support strong plasmon confinement with an acoustic plasmon mode in the short‐wave infrared region, but also provide ultrahigh nonlinear responses. The acoustic MXene plasmons (AMPs) in the MXene (Ti 3 C 2 T x )–insulator (SiO 2 )–metal (Au) nanostructure generate in the 1.5–6.0 µm wavelength range, exhibiting a two orders of magnitude reduction in wavelength compared to wavelength in free space. Furthermore, AMP resonators with patterned Au rods exhibit a record‐high nonlinear absorption coefficient of 1.37 × 10 −2 m W −1 at wavelength of 1.56 µm, ≈3 orders of magnitude greater than the highest value recorded for other 2D materials. These results indicate that MXenes can overcome fundamental plasmon wavelength limitations of previously studied 2D materials, providing groundbreaking opportunities in nonlinear optical applications, including all‐optical processing and ultrafast optical switching.