Dan Hua

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.

Green Layer-by-Layer Method for the Preparation of Polyacrylonitrile-Supported Zinc Benzene-1,4-dicarboxylic Acid Membranes

Ultrafiltration-level polyacrylonitrile (PAN) flat sheet membranes were chemically modified through cross-linking and hydrolysis to provide a suitable surface for the growth of a selective layer composed of a Zn benzene-1,4-dicarboxylic acid (Zn(BDC)) metal-organic framework (MOF). Unlike typical membrane modification methods or conventional MOF synthesis procedures, deionized (DI) water was the only solvent used for each of the modification steps. To better understand the layer-by-layer MOF growth process, several MOF growth conditions were also studied, including the effects of solution concentration, growth temperature, membrane immersion time and the number of layers. Subsequently, organic solvent nanofiltration (OSN) was used to test the effectiveness of the modifications and compare the performances of the fabricated membranes. With the appropriate combination of the MOF growth conditions, the layer-by-layer method was used to produce an OSN membrane with an isopropanol permeance of 2.39 L m-2  h-1  bar-1 and an 86 % rejection of the dye Brilliant Blue R (Mw 825.97 g mol-1 ).