During his scholarship at the Bénédictins of the Abbaye de Maredsours, Gaston-François met the British zoologist George Albert Boulenger, who came to study fossils from Denée.
He worked at the British Museum of Natural history where Boulenger taught him technical preparations of zoological collections.
He brought back 25,000 specimens, mostly snakes and fish, but also an ethnographic ensemble and many photos, leaving everything to the Museum of the Belgian Congo.
Nominated in 1927 as a definitive member, after Jean-Marie Derscheid left, he became in 1936 head of the zoology and entomology sections.
From August 1930 to September 1931, he went on a mission to Katanga, finding zoological and botanical specimens, but also cultural artifacts.