Modulator‐Controlled Synthesis of Microporous STA‐26, an Interpenetrated 8,3‐Connected Zirconium MOF with the the‐i Topology, and its Reversible Lattice Shift

A fully interpenetrated 8,3‐connected zirconium MOF with the the‐i topology type, STA‐26 (St Andrews porous material‐26), has been prepared using the 4,4′,4“‐(2,4,6‐trimethylbenzene‐1,3,5‐triyl)tribenzoate (TMTB) tritopic linker with formic acid as a modulating agent. In the as‐prepared form STA‐26 possesses Im3‾ m symmetry compared with the Pm3‾ m symmetry of the non‐interpenetrated analogue, NU‐1200, prepared using benzoic acid as a modulator. Upon removal of residual solvent there is a shift between the interpenetrating lattices and a resultant symmetry change to Cmcm which is fully reversible. This is observed by X‐ray diffraction and 13C MAS NMR is also found to be remarkably sensitive to the structural transition. Furthermore, heating STA‐26(Zr) in vacuum dehydroxylates the Zr6 nodes leaving coordinatively unsaturated Zr4+ sites, as shown by IR spectroscopy using CO and CD3CN as probe molecules. Nitrogen adsorption at 77 K together with grand canonical Monte Carlo simulations confirms a microporous, fully interpenetrated, structure with pore volume 0.53 cm3 g−1 while CO2 adsorption at 196 K reaches 300 cm3 STP g−1 at 1 bar. While the pore volume is smaller than that of its non‐interpenetrated mesoporous analogue, interpenetration makes the structure more stable to moisture adsorption and introduces shape selectivity in adsorption. Two‐in‐one A zirconium MOF with the topology is prepared in interpenetrated form by choice of modulator: combined XRD and MAS NMR reveal the interpenetrated lattices display a relative shift that is reversible upon polar sorbate uptake and removal.