All-gas-phase synthesis of UiO-66 through modulated atomic layer deposition

Abstract

Thin films of stable metal-organic frameworks (MOFs) such as UiO-66 have enormous application potential, for instance in microelectronics. However, all-gas-phase deposition techniques are currently not available for such MOFs. We here report on thin-film deposition of the thermally and chemically stable UiO-66 in an all-gas-phase process by the aid of atomic layer deposition (ALD). Sequential reactions of ZrCl ₄ and 1,4-benzenedicarboxylic acid produce amorphous organic–inorganic hybrid films that are subsequently crystallized to the UiO-66 structure by treatment in acetic acid vapour. We also introduce a new approach to control the stoichiometry between metal clusters and organic linkers by modulation of the ALD growth with additional acetic acid pulses. An all-gas-phase synthesis technique for UiO-66 could enable implementations in microelectronics that are not compatible with solvothermal synthesis. Since this technique is ALD-based, it could also give enhanced thickness control and the possibility to coat irregular substrates with high aspect ratios.

Abstract

Thin films of metal-organic frameworks (MOFs) are promising for catalysis, gas storage, and microelectronics. Here, the authors introduce a vapour-phase synthesis of UiO-66 thin films, beginning with modulated atomic layer deposition of porous, amorphous films, followed by acetic acid vapour-enabled crystallization to the MOF structure.