Microporous metal-organic frameworks (MOFs) that display permanent porosity show great promise for a myriad of purposes. The potential applications of MOFs can be developed further and extended by encapsulating various functional species (for example, nanoparticles) within the frameworks. However, despite increasing numbers of reports of nanoparticle/MOF composites, simultaneously to control the size, composition, dispersed nature, spatial distribution and confinement of the incorporated nanoparticles within MOF matrices remains a significant challenge. Here, we report a controlled encapsulation strategy that enables surfactant-capped nanostructured objects of various sizes, shapes and compositions to be enshrouded by a zeolitic imidazolate framework (ZIF-8). The incorporated nanoparticles are well dispersed and fully confined within the ZIF-8 crystals. This strategy also allows the controlled incorporation of multiple nanoparticles within each ZIF-8 crystallite. The as-prepared nanoparticle/ZIF-8 composites exhibit active (catalytic, magnetic and optical) properties that derive from the nanoparticles as well as molecular sieving and orientation effects that originate from the framework material.

Permanently microporous metal-organic framework (MOF) materials 1 have attracted considerable attention on account of their large internal surface areas, uniform channels, (sub)nanometer-sized cavities, thermal stability, and chemical tailorability. 2 Among the potential applications for which proof-of-concept reports have proliferated are gas storage, 3 chemical catalysis, 4 and smallmolecule separations. 5 At first glance MOFs would also appear to be attractive for chemical sensing. Nevertheless, reports of MOFbased sensing are comparatively few. 6 The challenge is signal transduction: the cavities of MOFs are generally too small to tailor with reporter molecules, i.e. moieties that can readily signal analytebinding events via changes in color, redox potential, or other properties. In the handful of cases where sensing has been described, advantage has generally been taken of framework luminescence, 7 with signal transduction consisting of luminescence quenching. 6,8 Here we describe an alternative approach that circumvents the need for molecular-level reporters and instead relies upon a readout of changes in a macroscopic property of the sensing material, the refractive index. Specifically, we have configured the material as a transparent thin film on an appropriate support material (glass or silicon) and optically monitored the energies of Fabry-Pe ´rot interference peaks as a function of analyte exposure. 9 These peaks are observable when the thickness of a supported material is comparable to the wavelength of light (λ). Importantly, their energies also depend on the film's refractive index.

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The encapsulation of noble-metal nanoparticles (NPs) in metal-organic frameworks (MOFs) with carboxylic acid ligands, the most extensive branch of the MOF family, gives NP/MOF composites that exhibit excellent shape-selective catalytic performance in olefin hydrogenation, aqueous reaction in the reduction of 4-nitrophenol, and faster molecular diffusion in CO oxidation. The strategy of using functionalized cavities of MOFs as hosts for different metal NPs looks promising for the development of high-performance heterogeneous catalysts.

Nanoscale metal-organic particles (NMOPs) are constructed from metal ions and organic bridging ligands via the self-assembly process. Herein, we fabricate NMOPs composed of Mn(2+) and a near-infrared (NIR) dye, IR825, obtaining Mn-IR825 NMOPs, which are then coated with a shell of polydopamine (PDA) and further functionalized with polyethylene glycol (PEG). While Mn(2+) in such Mn-IR825@PDA-PEG NMOPs offers strong contrast in T1-weighted magnetic resonance (MR) imaging, IR825 with strong NIR optical absorbance shows efficient photothermal conversion with great photostability in the NMOP structure. Upon intravenous injection, Mn-IR825@PDA-PEG shows efficient tumor homing together with rapid renal excretion behaviors, as revealed by MR imaging and confirmed by biodistribution measurement. Notably, when irradiated with an 808 nm laser, tumors on mice with Mn-IR825@PDA-PEG injection are completely eliminated without recurrence within 60 days, demonstrating the high efficacy of photothermal therapy with this agent. This study demonstrates the use of NMOPs as a potential photothermal agent, which features excellent tumor-targeted imaging and therapeutic functions, together with rapid renal excretion behavior, the latter of which would be particularly important for future clinical translation of nanomedicine.