Deposition of microcrystalline [Cu3(btc)2] and [Zn2(bdc)2(dabco)] at alumina and silica surfaces modified with patterned self assembled organic monolayers: evidence of surface selective and oriented growth

Abstract

The deposition of microcrystalline, phase pure [Cu₃(btc)₂] (1) and [Zn₂(bdc)₂(dabco)] (2) under solvothermal conditions on alumina and on silica surfaces modified with self assembled organic monolayers has been studied. The growth of 1 is remarkably surface selective and does not take place on silica but does on alumina. In contrast the growth of 2 is not surface selective at all and densely packed coatings were obtained on silica and on alumina surfaces. Most interestingly, [Cu₃(btc)₂] shows an oriented growth mode on both c-plane sapphire and COOH-terminated SAMs at SiO₂/Si(100) wafers. The single crystals of 1 are attached to the organic surface via the (111) face, while on c-plane sapphire the crystals interact via the (100) lattice plane leading to different shapes of the crystals: pyramids on sapphire and fully developed octahedra on the COOH-SAM. The gas adsorption properties of the obtained coatings were demonstrated by reversible loading with water and with pyridine in the case of 1 and loading with [(η⁵-C₅H₅)Pd(η³-C₃H₅)] as a typical example of a MOCVD precursor for both 1 and 2 which allows the fabrication of Pd nanoparticle loaded MOF thin films.