Due to the rapidly growing interest in development of silsesquioxane chemistry, we present herein an original approach to the synthesis of functionalized silsesquioxanes via dehydrogenative coupling of completely and incompletely condensed POSS silanols using a wide range of commercially available, non-toxic hydrosilanes and pinacolborane. Of particular importance, this procedure involves an inexpensive and abundant potassium tert-butoxide as a catalyst and undergoes under mild reaction conditions. No toxic metal residue or corrosive by-products are formed during this process, which makes this method highly convenient and practical. (C) 2019 Elsevier Inc. All rights reserved.