Hierarchically porous metal–organic frameworks with red topology for hydrogen and methane storage

Abstract

The construction of highly porous metal–organic frameworks with complex topologies requires precise matching between linker conformation and node connectivity. Here we report the reticular design and synthesis of CU-6-M (M = Fe or Cr), assembled from conformationally adaptive diphenylethynyl linkers and six-connected trinuclear oxo-centred clusters. The ability of the linker to adopt multiple out-of-plane conformations satisfies the geometric requirements of a red topology, resulting in a highly interconnected hierarchical pore architecture. CU-6-Fe and CU-6-Cr exhibit an interconnected hierarchical pore system with Brunauer–Emmett–Teller surface areas up to 7,145 m2 g−1. This architecture enables total H2 uptakes of up to 17.5 wt% and 45.4 g l−1 at 100 bar and 77 K. Under temperature–pressure swing conditions, CU-6-Fe and CU-6-Cr deliver up to 16.9 wt% and 44.1 g l−1 and also show record gravimetric CH4 storage at ambient temperature. These results establish linker flexibility as a key design parameter for the realization of complex, highly porous topologies for high-capacity storage of clean-energy fuel gases.