Molecular rotors and motors in dynamic and responsive porous architectures

Porous frameworks provide a robust platform for organizing the spatial arrangement of molecular rotors and motors in the solid state, thus fostering the emergence of collective phenomena and correlated motion. We reported on the benchmark dynamics of molecular rotors within a cubic zinc metalorganic framework.[1] Indeed, H T relaxation NMR and muon-spin spectroscopy, conducted down to a temperature of 2 K, revealed hyperfast rotary motion in the gigahertz regime even at temperatures as low as 2 K, with a negligible energy barrier (E ) of 6.2 cal mol . A functional organization of dipolar molecular rotors was achieved in a fluorinated metal-organic framework comprising a wheel-shaped ligand with geminal rotating fluorine atoms.[2] The combination of high-resolution synchrotron-source XRD and solid-state NMR spectroscopy at temperatures below the liquid He, along with DFT and phonon calculations, unveiled a highly dynamic landscape demonstrating benchmark mobility of correlated dipolar rotors at 2 K (E = 17 cal mol ). Highly porous yet stable architectures, referred to as porous switchable frameworks (PSFs), have been designed to sustain the effective isomerization of molecular switches and motors in the solid state.[3,4] The quantitative and reversible photo-isomerization of overcrowded alkene switches led to a restructuring of the framework, enabling "on-command" modulation of the adsorption properties. Notably, installing two orthogonal types of photoswitches in an integrated solid porous framework allowed the selective switching between four independently accessible states of the porous material, providing a basis for dynamic multifunctional materials. [1] Nature Chem. 2020, 12, 845; [2] Angew. Chem, Int. Ed. 2023, 62, 5, e202215893; [3] Nature Chem. 2020, 12, 595: [4] Angew. Chem, Int. Ed. 2023, 63, 23, e202404878