This review article presents the fundamental and practical aspects of water adsorption in Metal-Organic Frameworks (MOFs). The state of the art of MOF stability in water, a crucial issue to many applications in which MOFs are promising candidates, is discussed here. Stability in both gaseous (such as humid gases) and aqueous media is considered. By considering a non-exhaustive yet representative set of MOFs, the different mechanisms of water adsorption in this class of materials are presented: reversible and continuous pore filling, irreversible and discontinuous pore filling through capillary condensation, and irreversibility arising from the flexibility and possible structural modifications of the host material. Water adsorption properties of more than 60 MOF samples are reported. The applications of MOFs as materials for heat-pumps and adsorbent-based chillers and proton conductors are also reviewed. Some directions for future work are suggested as concluding remarks.

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Multimodal bioimaging nanoparticles by integrating diverse imaging ingredients into one system, represent a class of emerging advanced materials that provide more comprehensive and accurate clinical diagnostics than conventional contrast agents. Here monodisperse and biocompatible core-shell nanoparticles, NaGdF4: Yb(3+)/Er(3+)@NaGdF4:Nd@sodium-gluconate (termed as GNa-Er@Nd), with about 26 nm in diameter were successfully prepared by a facile two step reactions in high boiling solvents, and followed a ligand exchange process with sodium gluconate. The resulting GNa-Er@Nd nanoparticles were well characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR), and zeta potentials. These nanohybrids present brightly dual-wavelength excited upconversion luminescence (UCL) under both 980 and 793 nm laser because of the synergistic effect of Yb(3+)/Er(3+) and Nd(3+). They also exhibited excellent relaxivity parameters (r1) in magnetic resonance imaging (MRI) and Hounsfield units (HU) in X-ray computed tomography (CT) that are comparable to the clinical contrast agents. Therefore, these small and monodisperse nanoparticles provide options to construct a unique platform for potential multimodal UCL/CT/MRI imaging simultaneously.