Topological Transformation and Dimensional Reduction in Multicomponent Metal-Organic Frameworks for Gas Separations

Multicomponent MOFs have offered a wide range of opportunities to harness new properties. However, the synthesis of multicomponent MOFs remains challenging. This work demonstrates the synthesis of a family of multicomponent MOFs by topological transformation from well-established multicomponent partitioned acs (pacs) structures. Such transformation is based on the new understanding on the self-assembly process of pacs MOFs. A key to this understanding is that pacs structures, topologically regarded as the introduction of a pore-partitioning ligand into MOF-235/MIL-88 type framework, are likely to be formed in a layer-pillar-layer fashion in practical reactions. As the π-π interaction between layers and other chemical interactions during the self-assembly process are recognized, the structural transformation can be modulated from 3D pacs structures to 2D interrupted pacs structures (denoted i-pacs). It is especially noteworthy that such dimensional reduction is first observed in metal-organic frameworks and the i-pacs MOFs contain four structural modules and up to five components, which have the highest complexity among 2D MOFs. Interestingly, the i-pacs MOFs have significantly enhanced performance for CO₂/N₂ separation in comparison with pacs MOFs.