Stimuli-responsive structural transformations are emerging as a scaffold to develop a charming class of smart materials. A EuL metal-organic framework (MOF) undergoes a reversible temperature-stimulated single-crystal to single-crystal transformation, showing a specific behavior of fast capture/release of free Eu³⁺ in the channels at low and room temperatures. At room temperature, compound 1a is obtained with one free carboxylate group severing as further hook, featuring one-dimensional square channels filled with intrinsic free europium ions. Trigged by lowering the ambient temperature, 1b is gained. In 1b, the intrinsic free europium ions can be fast captured by the carboxylate-hooks anchored in the framework, resulting in the structural change and its channel distortion. To the best of our knowledge, this is the first report of such a rapid and reversible switch stemming from dynamic control between noncovalent and covalent Eu–ligand interactions. Utilizing EuL MOF to detect highly explosive 2,4,6-trinitrophenol at room temperature and low temperature provides a glimpse into the potential of this material in fluorescence sensors.

Limited therapeutic efficiency and severe side effects in patients are two major issues existing in current chemotherapy of cancers in clinic. To design a proper theranostic platform seems thus quite needed to target cancer cells accurately by bioimaging and simultaneously release drugs on demand without premature leakage. A novel ZnO-functionalized upconverting nanotheranostic platform has been fabricated for clear multi-modality bioimaging (upconversion luminescence (UCL), computed tomography (CT), and magnetic resonance imaging (MRI)) and specific pH-triggered on-demand drug release. In our theranostic platform multi-modality imaging provides much more detailed and exact information for cancer diagnosis than single-modality imaging. In addition, ZnO can play the role of a “gatekeeper” to efficiently block the drug in the mesopores of the as-prepared agents until it is dissolved in the acidic environment around tumors to realize sustained release of the drug. More importantly, the biodegradable ZnO, which is non-toxic against normal tissues, endows the as-prepared agents with high therapeutic effectiveness but very low side effects. These findings are of great interests and will inspire us much to develop novel effective imaging-guided on-demand chemotherapies in cancer treatment.

We report the synthesis and characterization of cubic NaGdF₄:Yb/Tm@NaGdF₄:Mn core–shell structures. By taking advantage of energy transfer through YbTmGdMn in these core–shell nanoparticles, we have realized upconversion emission of Mn²⁺ at room temperature in lanthanide tetrafluoride based host lattices. The upconverted Mn²⁺emission, enabled by trapping the excitation energy through a Gd³⁺ lattice, was validated by the observation of a decreased lifetime from 941 to 532 μs in the emission of Gd³⁺ at 310 nm (⁶P_7/2⁸S_7/2). This multiphoton upconversion process can be further enhanced under pulsed laser excitation at high power densities. Both experimental and theoretical studies provide evidence for Mn²⁺ doping in the lanthanide-based host lattice arising from the formation of F⁻ vacancies around Mn²⁺ ions to maintain charge neutrality in the shell layer.

We report the synthesis and characterization of cubic NaGdF₄:Yb/Tm@NaGdF₄:Mn core–shell structures. By taking advantage of energy transfer through YbTmGdMn in these core–shell nanoparticles, we have realized upconversion emission of Mn²⁺ at room temperature in lanthanide tetrafluoride based host lattices. The upconverted Mn²⁺emission, enabled by trapping the excitation energy through a Gd³⁺ lattice, was validated by the observation of a decreased lifetime from 941 to 532 μs in the emission of Gd³⁺ at 310 nm (⁶P_7/2⁸S_7/2). This multiphoton upconversion process can be further enhanced under pulsed laser excitation at high power densities. Both experimental and theoretical studies provide evidence for Mn²⁺ doping in the lanthanide-based host lattice arising from the formation of F⁻ vacancies around Mn²⁺ ions to maintain charge neutrality in the shell layer.

A sensor with a red-emission signal is successfully obtained by the solvothermal reaction of Eu³⁺ and heterofunctional ligand bpydbH₂ (4,4′-(4,4′-bipyridine-2,6-diyl) dibenzoic acid), followed by terminal-ligand exchange in a single-crystal-to-single-crystal transformation. As a result of treatments both before and after the metal–organic framework formation, accessible Lewis-base sites and coordinated water molecules are successfully anchored onto the host material, and they act as signal transmission media for the recognition of analytes at the molecular level. This is the first reported sensor based on a metal–organic framework (MOF) with multi-responsive optical sensing properties. It is capable of sensing small organic molecules and inorganic ions, and unprecedentedly it can discriminate among the homologues and isomers of aliphatic alcohols as well as detect highly explosive 2,4,6-trinitrophenol (TNP) in water or in the vapor phase. This work highlights the practical application of luminescent MOFs as sensors, and it paves the way toward other multi-responsive sensors by demonstrating the incorporation of various functional groups into a single framework.

Mastery of nanomaterial structure enables the control of its properties to enhance its performance for a given application. Herein, we demonstrate a fast and facile self-assembly method for the synthesis of a series of Co₃O₄@CeO₂ core@shell cubes, which are characterized by SEM, TEM, XRD, inductively coupled plasma mass spectrometry (ICP-MS), and X-ray photoelectron spectroscopy (XPS) analyses. The results indicate that the thickness of the CeO₂ shell can be tuned through simple variation of the feeding molar ratio of Ce/Co. These Co₃O₄@CeO₂ core@shell cubes are used for catalytic CO oxidation and show good catalytic properties. Moreover, the relationship between the catalytic performance and the CeO₂ shell thickness is studied in depth to optimize the catalytic properties.