Hyperpolarized Xe NMR signal advancement by metal-organic framework entrapment in aqueous solution

Abstract

We report hyperpolarized Xe signal advancement by metal-organic framework (MOF) entrapment (Hyper-SAME) in aqueous solution. The129Xe NMR signal is drastically promoted by entrapping the Xe into the pores of MOFs. The chemical shift of entrapped129Xe is clearly distinguishable from that of free129Xe in water, due to the surface and pore environment of MOFs. The influences from the crystal size of MOFs and their concentration in water are studied. A zinc imidazole MOF, zeolitic imidazole framework-8 (ZIF-8), with particle size of 110 nm at a concentration of 100 mg/mL, was used to give an NMR signal with intensity four times that of free129Xe in water. Additionally, Hyper-SAME is compatible with hyperpolarized129Xe chemical exchange saturation transfer. The129Xe NMR signal can be amplified further by combining the two techniques. More importantly, Hyper-SAME provides a way to make detection of hyperpolarized129Xe in aqueous solution convenient and broadens the application area of MOFs.