Brüll was called as rabbi to Bzenec, one of the Reform communities of Moravia, an office that be resigned in 1870 in order to take charge of the rabbinate of Frankfurt am Main.
As a result of the movement inaugurated by Samson Raphael Hirsch at Frankfurt, even the circles that were not Orthodox tended gradually toward the conservative party.
Brüll's range of reading and critical insight constituted him an important reviewer of new books in the field of Jewish science.
At the instance of Steinschneider, the Zunz-Stiftung had commissioned Brüll to add a supplement to Leopold Zunz's Gottesdienstliche Vorträge, the basic work of modern Jewish science.
): "Dr. Brüll appeared to me to possess the rare combination of ability and leisure, zeal and perseverance, requisite for editing such a supplement.'"
Of these, Toledot Shabbethai Ẓebi (Wilna, 1879) and Ner la-Maor, a biography of Aaron Worms, in Ozar ha-Sifrut, ii.