Leemans obtained his Licence en Sciences Mathématiques at the Université libre de Bruxelles in 1994 and his doctorate degree, under the supervision of Francis Buekenhout and Michel Dehon in 1998.
[1][2] He is currently Professor at the mathematics department of the Faculty of Sciences of the Université libre de Bruxelles.
He returned to Belgium after experiencing problems with Immigration New Zealand because of his stepson's autism.
[4] Leemans's principal area of research is at the interface of algebra, computational mathematics, combinatorics and geometry.
He has published more than 90 papers in peer-reviewed scientific journals and two memoirs of the Academie Royale des Sciences de Belgique.