Facile synthesis of crack-free metal-organic framework films on alumina by a dip-coating route in the presence of polyethylenimine

A facile polyethylenimine (PEI)-assisted dip-coating method allows crack-free films of MIL-101(Cr) and MIL-101(Cr)-NH2 to be prepared on alumina supports. The presence of PEI enhances the selectivity of the films for CO2 with respect to N-2. The film surfaces can be made hydrophobic by further dip-coating with an aliphatic monocarboxylic acid.