The brake pads would never line up. Mountain bikes usually have 26 inch rims while hybrid and road bikes use either 27 inch or 700 centimeters. In your place I just replace the back rim with a similar unit.
By the way you can get either slick or road type tread tires for a 26 inch rim. They ride pretty well too.
Most mountain bikes tires are 26", while some are 29", and road bikes use 29". Even if the rim would fit, I don't know if the brakes would fit or if the hub sizes are the same.
You could find some mtb rims that are narrow, while most can handle a 1.5" tire, maybe some could use a smaller one.