Actions of sl_2 on algebras appearing in categorification

We prove that many of the recently-constructed algebras and categories which appear in categorification can be equipped with an action of $\mathfrak{sl}_2$ by derivations. The $\mathfrak{sl}_2$ representations which appear are filtered by tensor products of coverma modules. In a future paper, we will address the implications of the $\mathfrak{sl}_2$ structure for categorification.