Mixed-Linker Metal-Organic frameworks for carbon and hydrocarbons capture under moist conditions

Abstract

• MOF-801-FA were synthesised via utilizing a mixed-ligand strategy. • Gas adsorption was boosted, e.g., a 2.5-fold increase for methane capture. • Prominent IAST selectivities were witnessed for CH 4 /N 2 and CO 2 /N 2 mixture. • MOF-801-FA reveal clean and sharp separations in a high relative humidity. The capture of carbon and hydrocarbons is significant to the utilization of valuable resources and the mitigation of global warming, but achieving high gas capacity and selectivity at the same time remains a challenge, especially in the presence of high humidity. In this regard, based on the building block of MOF-801, MOF-801-FA structures were synthesized with high quality and few defects through a mixed-ligand strategy, in which formate ligands were introduced into the framework apart from fumarate ligands. This brought about tremendous increases in gas adsorption capacity, e.g., ca. 2.5-fold and 1.1-fold enhancement occurred to the adsorption of CH 4 and CO 2 in MOF-801-Hf-FA than MOF-801-Hf at 298 K and 1 bar. Besides, prominent IAST selectivities were also witnessed in MOF-801-FA, higher than those in the pristine MOFs, for CH 4 /N 2 and CO 2 /N 2 mixtures under ambient conditions. We then confirmed the efficient performance of MOF-801-FA for real CH 4 /N 2 and CO 2 /N 2 mixtures using the breakthrough experiments and following cycling tests, even in a relative humidity of 90%. Thus, the mixed-linker strategy was demonstrated effective to tune the structures of MOFs, and boost their performance in gas adsorption and separation. The results also showed that, with high capacities for CH 4 and CO 2 , superior selectivities over N 2 , desirable water resistance and facile regeneration, MOF-801-M−FA (M = Zr or Hf) are promising candidates for capturing CH 4 and CO 2 from N 2 in industry.