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High-efficiency separation of hexane isomers through selective molecular exclusion represents an important yet challenging task in the petrochemical industry. It has stringent requirements on the adsorbents' pore shape and dimensions. Here we report the complete exclusion of branched hexanes from their linear isomer by an aluminum metal−organic framework, CAU-21-ODB (ODB = 4,4′-oxidibenzoate) with high stability. The unique gourd-shaped channels with suitable pore aperture lead to substantial uptake of nHEX (141 mg/g at 30 °C) but negligible adsorption of its branched isomers under identical conditions. The capability of CAU-21-ODB for the separation of hexane isomers has been verified by multicomponent breakthrough experiments. DFT calculations further confirm the size-exclusion-based separation mechanism.

Formaldehyde (HCHO) is one of the most universal and harmful indoor gas pollutants nowadays. Even a very low concentration of HCHO does great harm to human health. Herein, we developed a kind of porous organic polymer (P-CDP) as an adsorbent for the rapid removal of HCHO. The adsorption capacity of HCHO on P-CDP is 2.78 mg g −1 and the average adsorption rate in 10 min is 0.18 mg g −1 min −1 at a HCHO concentration of 1 ppm, which are 4.06 and 9.11 times higher than those of commercial coconut shell activated carbon (ACCO), respectively. The partition coefficient (PC) of P-CDP reaches 0.93 mol kg −1 Pa −1 . More importantly, P-CDP shows excellent reusability, with no obvious loss of HCHO uptake after five adsorption−desorption cycles, indicating the good cycling stability of P-CDP. The high adsorption uptake and rapid adsorption rate of P-CDP for HCHO are attributed to the relatively strong electrostatic interactions together with the van der Waals forces between −F and −OH groups on P-CDP and HCHO molecules. This study demonstrates the great potential of P-CDP for practical use in the removal of low-concentration HCHO in indoor environments.

The effect of metal modulation on the SO2 adsorption and separation performance of MOF materials.

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