Butanol Isomer Recognition by a Flexible Hydrogen-Bonded Organic Framework

The search for new materials capable of molecular recognition remains an ongoing challenge. In particular, structural isomers are in demand due to nearly identical physicochemical properties. Here, we report a crystalline, flexible, hydrogen-bonded organic framework (HOF), DUT-226, synthesized from a carbazole-based tetracarboxylic acid. It exhibits permanent microporosity with a BET area of 1474 m2 g–1, specific pore volume of 0.63 cm3 g–1, and a pore-limiting diameter of 12 Å. DUT-226 is able to discriminate among butanol isomers in the vapor phase based on their adsorption capacities. Vapor adsorption experiments at 298 K reveal an isomer-dependent adsorption capacity trend, whereas the adsorption capacity is significant for n-butanol and almost negligible for iso-butanol. Such differences in adsorption could be attributed to the selective solid-state phase transitions of DUT-226 in the presence of different butanol isomers. These results establish DUT-226 as the first HOF material potentially capable of molecular recognition of alcohol isomers.