The ideal gas equation is written as PV = nRT.

Pressure has units of force/area, or forc/(length²). Volume has units of length³. So, the dimensions are force * length, which is the same as energy.

So, liter-atmospheres is an energy unit.

This makes mol-kelvins also an energy unit. Further, it means that R is a conversion constant that converts from one set of enrgy units into another!