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

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 CH4 and CO2 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 CH4/N-2 and CO2/N-2 mixtures under ambient conditions. We then confirmed the efficient performance of MOF-801-FA for real CH4/N-2 and CO2/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 CH4 and CO2, superior selectivities over N-2, desirable water resistance and facile regeneration, MOF-801-M-FA (M = Zr or Hf) are promising candidates for capturing CH4 and CO2 from N-2 in industry.