One of the greatest advantages of augmented reality (AR) in education is that AR increases student motivation. Nevertheless, there is a gap between the research on student motivation in AR and the definition of frameworks to inform and guide the design and development of AR applications that effectively support student motivation. In this paper, we attempt to bridge that gap as we introduce and evaluate a framework for designing motivational AR applications. Our framework has been built upon three theoretical foundations: motivational design, universal design for learning and co-creation. The evaluation study was conducted with 58 chemistry students enrolled in the vocational education and training (VET) program for Laboratory Operations, and we found that the framework not only effectively supports the four dimensions of Keller's (2010) ARCS (attention, relevance, confidence and satisfaction) model of motivation, but also demonstrates exceptional results in the Attention and Confidence dimensions of motivation.