Temperature-Responsive Smart Molecule Gate in Metal-Organic Framework for Task-Specific Gas Separation
Molecular sieving is a highly efficient method for gas separation because of ultra-high selectivity. Nevertheless, traditional adsorbents with molecular sieving effect can only separate a specific gas mixture due to their constant pore apertures. It is still a challenge to continuously fine-tune pore apertures at sub angstrom scale to separate various gas mixtures in a given porous material. Herein, temperature-responsive smart molecule gate with precisely controllable pore size is proposed and validated for molecule recognition and separation, achieved by introducing methoxyl group in the narrow bottleneck of the metal-organic framework (MOF). The effective aperture size of the smart molecule gate can be continuously tuned from 3.6 to 5.2 Å, covering the size range of the commercially important gas molecules. Consequently, the MOF with such structure exhibits highly selective uptake for several gas mixtures, including N2/CH4, CH4/C2H4, C2H4/C3H6, C3H6/C3H8, and C3H8/i-C4H10, by controlling the opening degree of smart molecule gate. Furthermore, to verify the practical application, C3H6/C3H8 separation performances were systematical evaluated, and excellent selectivity for C3H6/C3H8 can be achieved at room temperature. This rational design of smart molecule gate in this work opens a new avenue for the application of smart materials for gas separation.