Formation and tuning of a pillar porous-layered framework into a pillar double-channelled framework

Precise structural regulation is crucial for tailoring the functions of metal-organic frameworks (MOFs). In this work, we report a subtle pillar-engineering strategy, which involves changing the hexafluoride anion from SiF₆^2- to TiF₆^2-, which can trigger a dramatic topological transformation in Cu-based MOFs constructed from 1,3,5-tris(2-methyl-1H-imidazol-1-yl)benzene (TMBIB). The resulting frameworks, Cu-TMBIB-a and Cu-TMBIB-b, exhibit entirely different network architectures: Cu-TMBIB-a adopts a classical pillar porous-layered structure with a 3,4,5-c topology, whereas Cu-TMBIB-b features a rare pillar-double-channelled framework with an 8,12-c topology. This distinct evolution in the framework architecture is hierarchically driven by the geometric and electronic disparities between the inorganic pillars, which regulate metal-node coordination and the subsequent assembly process. Notably, Cu-TMBIB-a shows good stability and favorable iodine adsorption performance. This work not only reveals pillar engineering as a powerful tool for MOF topology, but also expands the structural diversity of pillared frameworks, offering a rational design strategy for developing advanced separation materials.