Flexible porous molecular materials responsive to CO2, CH4 and Xe stimuli

摘要: In the search for flexible molecular crystals endowed with porosity, we achieved fabrication of expandable crystalline prototypal structures, which allow absorption gases, without modifying crystal architecture. The design brings together highly symmetrical tetrahedral elements to construct swellable porous adamantoid frameworks through co-operation eight surrounding hydrogen bonds mounted on conformationally groups. flexibility manifests itself in response stimuli selected promote reversible conformational changes, inducing breathing structure. backbone reticular construction is based formation carboxylic dimers, project outwards from core consolidate 3D framework. Contact proper gases such as CO2, Xe and hexane triggers a 56–70% enlargement channel cross-section. accommodation CO2 chambers was revealed by synchrotron-light X-ray diffraction, combined dynamics density functional theory (DFT) theoretical calculations. Rare experimental observations xenon dynamics, diffuses along channels experiences different chamber orientations crystal, were gathered analysing 129Xe NMR chemical shift anisotropy profiles, encode shape orientation each visited cavity channel. jump rate activation energy experienced uniquely established exploring atoms their diffusional path. Nitrogen showed low affinity matrix unable enlarge pores, thus it excluded restrictive pores empty crystal. Given properties crystals, possible outline some advantageous aspects, simple design, easy self-assembly, solubility, gas uptake absence metal ions, they can be considered eco-friendly capture separation.