Recent Advances of Multidentate Ligand-Based Anion-Pillared MOFs for Enhanced Separation and Purification Processes

As an important subclass of metal–organic frameworks (MOFs), anion-pillars MOFs (APMOFs) have recently exhibited exceptional performances in separation and purification processes. The adjustment of pore sizes and environments of APMOFs can be finely tuned through judicious combination of organic ligands, anion pillars, and metal ions. Compared to widely investigated anion pillars, organic ligands are more crucial as they allow for a broader range of pore sizes and environments at the nanometer scale. Furthermore, different from the bidentate ligand-based APMOFs that typically form three-dimensional (3D) frameworks with pcu topology, APMOFs constructed using multidentate nitrogen(N)-containing ligands (with a coordination number ≥ 3) offer opportunities to create APMOFs with diverse topologies. The larger dimensions and possible distortion of multidentate N-containing ligands prove advantageous for addressing multi-component hydrocarbon separations encompassing a broad spectrum of dynamic diameters. Therefore, this Review summarizes the structural characteristics of multidentate ligand-based APMOFs and their enhanced performances for gas separation and purification processes. Additionally, it discusses current challenges and prospects associated with constructing multidentate ligand-based APMOFs while providing prospects. This critical review will provide valuable insights and guides for designing and developing advanced multidentate ligand-based APMOF adsorbents.