Materials with good flexibility and high conductivity that can provide electromagnetic interference (EMI) shielding with minimal thickness are highly desirable, especially if they can be easily processed into films. Two-dimensional metal carbides and nitrides, known as MXenes, combine metallic conductivity and hydrophilic surfaces. Here, we demonstrate the potential of several MXenes and their polymer composites for EMI shielding. A 45-micrometer-thick Ti ₃ C ₂ T _x film exhibited EMI shielding effectiveness of 92 decibels (>50 decibels for a 2.5-micrometer film), which is the highest among synthetic materials of comparable thickness produced to date. This performance originates from the excellent electrical conductivity of Ti ₃ C ₂ T _x films (4600 Siemens per centimeter) and multiple internal reflections from Ti ₃ C ₂ T _x flakes in free-standing films. The mechanical flexibility and easy coating capability offered by MXenes and their composites enable them to shield surfaces of any shape while providing high EMI shielding efficiency.

Shields up!: Specialized conductive materials are used to shield or block electromagnetic radiation such as microwaves or radio waves to either prevent the escape of stray radiation or prevent interference from unwanted sources. Ideal materials should show high effective shielding while requiring a small volume or mass of material. Materials from the MXene family of two-dimensional ceramics, where M is a transition metal and X is either carbon or nitrogen, have shown excellent shielding properties. Iqbal et al. now show even better and somewhat unexpected performance from a metal carbon nitride. Science , this issue p. 446