Hierarchically structured mixed-linker HKUST-1 Metal Organic Frameworks as catalysts: One-pot synthesis of quinazolines

Abstract

Hierarchically structured HKUST-1 compounds have been prepared by a mixed-linker strategy starting from mixtures of trimesic (BTC) and 5-hydroxyisophtalic (OH-IP) acids in different proportions. Unlike purely microporous pristine HKUST-1, the mixed-linker compounds feature a micro-/mesoporous system in which mesopores account for up to 40% of the total pore volume of the solid. The creation of mesopores is reflected by the appearance of deep trenches running in well-defined directions, parallel to the edges of the octahedral crystal. This evidences that point defects introduced by the incorporation of OH-IP are not distributed randomly through the framework, but they tend to coalesce into line defects along the <1 1 0> direction. The creation of such a hierarchical system of mesopores translates into a higher catalytic activity of mixed-linker MOFs with respect to pristine HKUST-1 for the conversion of bulky substrates, as we showed for the synthesis of quinazoline by oxidative coupling of benzylamine and 2-aminoacetophenone with tert-butyl hydroperoxide.