Electrides, with excess electrons confined in interstitial spaces, are promising for the use in catalysis, electron emitters, superconductors, and spintronics. However, they tend to lack chemical stability and magnetism, which limits their practical applications. In this work, using the first-principles calculations, we report a scarce layered semiconducting electride CaCl with P3̅m1 symmetry. The exfoliated CaCl monolayer from the bulk retains the semiconducting electride with extremely low exfoliation energy (0.17 J/m2), high in-plane stiffness (24.35 N/m), high electron mobility (597 cm2 V−1 s−1), and low work function (3.67 eV). Such a CaCl electrene is confirmed to be thermodynamically stable by negative formation enthalpy, no imaginary frequency of phonon dispersion, ab initio molecular dynamics simulations. In addition, the BF4 adsorped CaCl electrene is a ferromagnetic half-metal with a net magnetic moment of 1 μB contributed by anionic electrons and a spin-minority bandgap. Thus, the CaCl electrene is a potential candidate for the applications of electron emitter, spin-injector and spintronics.