Single-Crystalline UiO-67-Type Porous Network Stable to Boiling Water, Solvent Loss, and Oxidation.

With methylthio groups flanking the carboxyl groups, the 3,3',5,5'-tetrakis(methylthio)biphenyl dicarboxylate (TMBPD) linker forms a zirconium(IV) carboxylate porous framework featuring the topology of the UiO-67 prototype, i.e., with a face-centered-cubic array of the Zr6O4(OH)4 clusters. Thioether functionalization proves valuable because the ZrTMBPD crystal is found to be exceptionally stable not only upon long-term exposure to air but also in boiling water and a broad range of pH conditions. The hydrophobicity of the metal-organic framework can also be tuned by simple H2O2 oxidation, as illustrated in the water contact-angle measurement of the pristine and H2O2-treated ZrTMBPD solid.

Metalation Triggers Single Crystalline Order in a Porous Solid.

We report the dramatic triggering of structural order in a Zr(IV)-based metal-organic framework (MOF) through docking of HgCl2 guests. Although as-made crystals were unsuitable for single crystal X-ray diffraction (SCXRD), with diffraction limited to low angles well below atomic resolution due to intrinsic structural disorder, permeation of HgCl2 not only leaves the crystals intact but also resulted in fully resolved backbone as well as thioether side groups. The crystal structure revealed elaborate HgCl2-thioether aggregates nested within the host octahedra to form a hierarchical, multifunctional net. The chelating thioether groups also promote Hg(II) removal from water, while the trapped Hg(II) can be easily extricated by 2-mercaptoethanol to reactivate the MOF sorbent.

Selective Ag(I) binding, H2S sensing, and white-light emission from an easy-to-make porous conjugated polymer.

Separating silver (Ag(+)) from lead (Pb(2+)) is one of the many merits of the porous polymer framework reported here. The selective metal binding stems from the well-defined chelating unit of N-heterocycles, which consists of a triazine (C3N3) ring bonded to three 3,5-dimethylpyrazole moieties. Such a rigid and open triad also serves as the distinct building unit in the fully conjugated 3D polymer scaffold. Because of its strong fluorescence and porosity (e.g., BET surface area: 355 m(2)/g), and because of the various types of metal species that can be readily taken up, this versatile framework is especially fit for functionalization. For example, with AgNO3 loaded, the framework solid exhibits a brown color in response to water solutions of H2S, even at the dilution of 5.0 µM (0.17 ppm); whereas cysteine and other biologically relevant thiols do not cause notable change in color. In another example, tunable white-light emission was produced when an Ir(III) complex was doped (e.g., about 0.02% of the polymer weight) onto the framework. Mechanistically, the bound Ir(III) centers become highly emissive in the orange-red region, complementing the broad, bluish emission from the polymer host to result in the overall white-light quality: the color attributes of the emission are therefore easily tunable by the Ir(III) dopant concentration. With this exemplary study, we intend to highlight metal uptake as an effective approach to modify and enrich the properties of porous polymer frameworks and to stimulate interest in further examining metal-polymer interactions in the context of sensing, separation, catalyzes, and other applications.

Effective mercury sorption by thiol-laced metal-organic frameworks: in strong acid and the vapor phase.

Free-standing, accessible thiol (-SH) functions have been installed in robust, porous coordination networks to provide wide-ranging reactivities and properties in the solid state. The frameworks were assembled by reacting ZrCl4 or AlCl3 with 2,5-dimercapto-1,4-benzenedicarboxylic acid (H2DMBD), which features the hard carboxyl and soft thiol functions. The resultant Zr-DMBD and Al-DMBD frameworks exhibit the UiO-66 and CAU-1 topologies, respectively, with the carboxyl bonded to the hard Zr(IV) or Al(III) center and the thiol groups decorating the pores. The thiol-laced Zr-DMBD crystals lower the Hg(II) concentration in water below 0.01 ppm and effectively take up Hg from the vapor phase. The Zr-DMBD solid also features a nearly white photoluminescence that is distinctly quenched after Hg uptake. The carboxyl/thiol combination thus illustrates the wider applicability of the hard-and-soft strategy for functional frameworks.

Bio-inspired stabilization of sulfenyl iodide RS-I in a Zr(IV)-based metal-organic framework.

A Zr(IV)-based metal-organic framework (MOF) appended with free-standing thiol (-SH) groups was found to react readily with I2 molecules to form sulfenyl iodide (S-I) units. In contrast to its solution chemistry of facile disproportionation into disulfide and I2, the sulfenyl iodide (SI) function, anchored onto the rigid MOF grid and thus prevented from approaching one another to undergo the dismutation reaction, exhibits distinct stability even at elevated temperatures (e.g., 90 °C). On a conceptual plane, this simple and effective solid host also captures the spatial confinement observed for the complex biomacromolecular scaffolds involved in iodine thyroid chemistry, wherein the spatial isolation and consequent stabilization of sulfenyl/selenenyl iodides are exerted by means of the protein scaffolds.

Low-temperature fabrication of brown TiO2 with enhanced photocatalytic activities under visible light.

Here we report a facile one-step low-temperature solution-based method to treat native TiO2 with NaH. The NaH treatment effectively induces the Ti(iii) species and oxygen vacancies into the TiO2 host lattice, and enables the absorption edge of TiO2 to be conveniently adjusted from the UV region to the red end of the visible spectrum.

Room-temperature acetylene hydration by a Hg(II)-laced metal-organic framework.

Thiol (-SH) groups within a Zr(IV)-based metal-organic framework (MOF) anchor Hg(II) atoms; oxidation by H2O2 then leads to acidic sulfonate functions for catalyzing acetylene hydration at room temperature.

Tackling poison and leach: catalysis by dangling thiol-palladium functions within a porous metal-organic solid.

Self-standing thiol (-SH) groups within a Zr(IV)-based metal-organic framework (MOF) anchor Pd(II) atoms for catalytic applications: the spatial constraint prevents the thiol groups from sealing off/poisoning the Pd(II) center, while the strong Pd-S bond precludes Pd leaching, enabling multiple cycles of heterogeneous catalysis to be executed.