A Porous Crystalline Molecular Solid Explored by Hyperpolarized Xenon We thank the Italian Ministry of Universities and Scientific Research (PRIN program) for financial support. The research with laser-polarized xenon was supported by the Director, Office of Energy Research, Office of Basic Energy Science, Materials Sciences Division of the U.S. Department of Energy. T.M. thanks the Alexander von Humboldt Foundation for

Abstract

Volatile species and large gas atoms, such as xenon, can diffuse into the aromatic nanochannels of a solid comprising tris(o-phenylenedioxy)cyclophosphazene molecules held together by weak interactions. Continuous-flow laser-polarized 129Xe NMR spectroscopy shows an anisotropic signal from the xenon atoms inside the crystals as soon as 200 ms after contact of the polarized gas with the sample. The xenon chemical shift anisotropy is concentration dependent (see picture) and undergoes a sign inversion as a result of the change of the symmetry of electron cloud.