Can I substitute pomegranate concentrate for pomegranate molasses in this recipe?

There isn't any reason why you couldn't, but I would have no idea how much to suggest. Pomegranate molasses is the regular strength juice cooked down to a syrup consistency, and for the most part that is what concentrate is. The only question is how much water was removed, and how concentrated it is. I suppose you could add water to it until is is sort of syrupy, and then use that. Do let the rest of us know what you do and how it goes.