Dicarboxylic Acid Separation by Dynamic and Size-Matched Recognition in Solution and in the Solid State

Bis(trimethylammonium) alkane diiodides dynamically encapsulate dicarboxylic acids through intermolecular hydrogen bonds between the I−anions of the hosts and the carboxylic OH groups of the guests. A selective recognition is realized when the size of the I−⋅⋅⋅HOOC(CH2/CF2)nCOOH⋅⋅⋅I−superanion matches the dication alkyl chain length. Dynamic recognition is also demonstrated in solution, where the presence of the size-matching organic salt boosts the acid solubility profile, thus allowing efficient mixture separation.