Precise Molecular Sieving Architectures with Janus Pathways for Both Polar and Nonpolar Molecules

Precise molecular sieving architectures with Janus superhighways are constructed via a molecularly engineered interfacial reaction between cyclodextrin (CD) and trimesoyl chloride (TMC). Interestingly, the CD/TMC nanofilms constructed with both hydrophobic inner cavities and hydrophilic channels exhibit exceptionally high permeances for both polar and nonpolar solvents. The precise molecular sieving functions are determined by the type of CD building blocks and the inner cavities of intrinsic 3D hollow bowls. Positron annihilation spectroscopy (PAS) confirms that a larger inner CD cavity tends to generate a larger free volume and higher microporosity. Based on the rejection ratio of various dyes, the estimated molecular weight cutoff of CD/TMC nanofilms follows the trend of α-CD/TMC (320 Da) <β-CD/TMC (400 Da) <γ-CD/TMC (550 Da), which is in strict accordance with the orders of their free volumes measured by PAS and inner cavity sizes of α-CD <β-CD <γ-CD. This kind of novel CD/TMC molecular sieving membrane with intrinsic microporosity containing tunable pore size and sharp pore-size distribution can effectively discriminate molecules with different 3D sizes.