Answer:
Love has been perhaps most usefully defined as a state of deep affection and devotion characterized uniquely by the condition that one would without hesitation put the welfare of the beloved ahead of one's own. Love can manifest in many forms, of which romantic sexual love is only one category. (You may love your sexual partner--or a family member--or a best friend--or an ideal, a concept, a place, a writer, a mentor, an activity--etc.)
Sex--or rather, specifically sexual act[s]--is a biological function, usually most satisfactorally requiring intimate personal contact of some sort, the occasions for which may likewise range widely: from the purely mutually recreational, to specifically for the purposes of procreation, to a form of the manifestation of the feelings of affection between people in a commited and caring relationship.