MgAPO-5 materials have been synthesized by using three new structure directing agents: S-(-)-1-benzyl-2-pyrrolidinemethanol, and its ortho-and meta-fluoro-benzyl derivatives. Their acidity has been measured and their catalytic activity tested in the cyclohexene oxide opening acidcatalyzed reaction. The catalytic activity of these materials can be related to their acidity. It has been found that MgAPO-5 samples synthesized from both fluorinated structure directing agents are much more active as acid catalysts for the reaction. A computational study based on molecular mechanics shows a rigid arrangement of the organic molecules in form of helices of dimers within the AFI structure, and suggests a direction of the fluorinated molecules towards the incorporation of magnesium atoms in the framework. (c) 2006 Elsevier B.V. All rights reserved.