Tailoring the dynamics of DUT-5 nanocrystals: from rigid nanoparticles to flexible nanowires

Here we describe the synthesis of a series of 1D anisotropic DUT-5(Al) nanostructures differing by their crystal dimensions and aspect ratio. Very long and monodisperse DUT-5(Al) nanowires (NWs) with length exceeding 6 µm were designed by using graphene oxide (GO) nanoscrolls as structure directing agents while shorter DUT-5(Al) nanorods 50 nm in length or polydisperse DUT-5(Al) samples with a broad size distribution were prepared without any GO. Remarkably, these materials were also differing by their dynamic properties upon guest molecules adsorption. While DUT-5(Al) nanorods exhibited a rigid large pore (lp) phase, it was revealed that DUT-5(Al) NWs could present a gating behaviour upon guest adsorption involving a structural transition from a highly disordered narrow pore (np) phase to the lp phase. The structure of DUT-5(Al) NWs as well as their guest-responsive structural flexibility were fully characterized by coupling high resolution TEM, 3D electron diffraction, high resolution synchrotron PXRD and PDF, adsorption isotherms and in situ PXRD. To the best of our knowledge, this study delivers an unprecedented design of flexible DUT-5(Al) NWs whereas this MOF was previously regarded as a rigid porous hybrid material. Moreover, it demonstrates that tuning the aspect ratio of MOF particles can influence their structural flexibility.