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 via a mixed-linker strategy starting from mixtures of trimesic (BTC) and 5-hydroxyisophthalic (OH-IP) acids in different proportions. Unlike purely microporous pristine HKUST-1, the mixed-linker compounds feature a hierarchical 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 demonstrates that point defects introduced by the incorporation of OH-IP are not distributed randomly throughout the framework, but they tend to coalesce into line defects along the 〈110〉 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.