Oriented growth of the functionalized metal–organic framework CAU-1 on –OH- and –COOH-terminated self-assembled monolayers

The oriented growth of the amino-functionalized metal-organic framework [Al4(OH)2(OCH3)4(H2N-bdc)3].xH2O (named CAU-1; CAU = Christian-Albrechts-University) on different self-assembled monolayers (SAMs) is reported. Gold substrates were modified with both 16-mercaptohexadecanol and 16-mercaptohexadecanoic acid SAMs and immersed in a pre-treated crystallization solution. The different terminal functionalities and synthesis parameters result in the direct surface growth of CAU-1 crystals along preferred crystallographic orientations. While for the OH-terminated SAMs a preferential attachment of the CAU-1 crystals either in [011] or [002] direction is observed (depending on the reaction conditions), highly oriented crystal growth in [002] orientation was obtained on the carboxylic acid functionalized SAMs.