Separation of d-glucose and d-fructose by porous organic cage

Porous organic cages (POCs) are discrete, three-dimensional molecular species constructed from organic building blocks via covalent bonds. In this work, we found that RCC3, a tetrahedral [4 + 6] porous organic cage possessing 6 vicinal diamine pairs, can selectively separate d -glucose and d -fructose. RCC3 exhibited high binding capacity for d -glucose (0.4 mg/mg of RCC3). This binding process can be reversibly controlled. After a capture-dissociation cycle, the recovery yields of d -glucose and RCC3 were 75% and 83%, respectively. In addition, three binding/dissociation experiments on the binary system of d -glucose and RCC3 demonstrated its reusability. The binding mechanism of RCC3 to d -glucose was investigated via nuclear magnetic resonance spectroscopy (NMR), matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS), and control experiments with various POCs and monosaccharides, revealing the aminal formation between diamines on RCC3 and the carbonyl group of d -glucose. This work demonstrated a novel strategy for the molecular recognition and isolation of d -glucose utilizing porous organic cages.