Ionic-liquid-assisted room-temperature dry etching of metal–organic frameworks

Metal–organic frameworks (MOFs) are functional nanoporous materials with high surface areas exhibiting great promise for diverse device applications. However, their beam-sensitive structure renders them highly susceptible to electron and ion beam damage, leading to decomposition during etching and hindering fine patterning. In this study, we developed a simple method for room-temperature dry etching of this fragile class of materials. By infiltrating MOFs with ionic liquids, their mechanical stability is greatly improved, and the damage from electron and ion beams is reduced, achieving harmless ion beam etching. Using this method, fine patterning of MOFs with sub-100-nm precision was successfully accomplished at room temperature. The influence of ionic liquid type on the dry etching properties of MOFs was studied, and possible damage mechanisms were suggested, involving reduction of Cu 2+ to Cu + and cleavage of the Cu–O bond.