An ultra-permeable hybrid Mg-MOF-74-Melamine sponge composite for fast dynamic gas separation

Abstract

Shape engineering porous solids such as metal-organic frameworks (MOFs) into hierarchical structured adsorbents allows significant process intensification. Here we propose a facile approach to obtain a mouldable structured adsorbent with high loading of porous solids by employing a commercially available low-cost melamine sponge. As a case study, Mg-MOF-74 was synthesized in an aqueous media at room temperature and coated successfully over the melamine sponge, without any pre-treatment/additive, to yield a melamine sponge-based Mg-MOF-74 composite (Mg-MOF-74@MS). Even after multiple coating steps, the composite displayed remarkable compressibility, thus providing additional degrees of freedom in designing packed bed systems over other rigid adsorbent forms and structures. The dynamic gas separation capability of the prepared Mg-MOF-74@MS composite was demonstrated via breakthrough experiments with mixtures of 20% CO2 and 80% CH4 at 1 bar and 298 K. Owing to the spatial structure of melamine sponge, the composite retained the adsorption properties of Mg-MOF-74 for CO2 capture i.e., high dynamic capacity (5.07 mmol/g), high selectivity (>100), facile regeneration and performed better than binderless Mg-MOF-74 pellets in terms of mass transfer, unused bed length (LUB) and pressure drop (large permeability). Overall, these findings open an interesting field of research with melamine sponge-based MOF structured adsorbent as a potential candidate for gas-phase adsorption-based separation applications.