  Using first-principles calculations, we predict a lightweight
room-temperature ferroelectric carbon-boron framework in a host/guest clathrate
structure. This ferroelectric clathrate, with composition ScB$_3$C$_3$,
exhibits high polarization density and low mass density compared with widely
used commercial ferroelectrics. Molecular dynamics simulations show spontaneous
polarization with a moderate above-room-temperature T$_c$ of $\sim$370 K, which
implies large susceptibility and possibly large electrocaloric and
piezoelectric constants at room temperature. Our findings open the possibility
for a new class of ferroelectric materials with potential across a broad range
of applications.
