Pyrolytic Depolymerization of Polyolefins Catalysed by Zirconium-based UiO-66 Metal-Organic Frameworks.

Polyolefins such as polyethylenes and polypropylenes are the most-produced plastic waste globally, yet are difficult to convert into useful products due to their unreactivity. Pyrolysis is a practical method for large-scale treatment of mixed, contaminated plastic, allowing for their conversion into industrially-relevant petrochemicals. Metal-organic frameworks (MOFs), despite their tremendous utility in heterogeneous catalysis, have been overlooked for polyolefin depolymerization due to their perceived thermal instabilities and inability of polyethylenes and polypropylenes to penetrate their pores.

MOF-Thermogel Composites for Differentiated and Sustained Dual Drug Delivery.

In recent years, multidrug therapy has gained increasing popularity due to the possibility of achieving synergistic drug action and sequential delivery of different medical payloads for enhanced treatment efficacy. While a number of composite material release platforms have been developed, few combine the bottom-up design versatility of metal-organic frameworks (MOFs) to tailor drug release behavior, with the convenience of temperature-responsive hydrogels (or thermogels) in their unique ease of administration and formulation. Yet, despite their potential, MOF-thermogel composites have been largely overlooked for simultaneous multidrug delivery.

UiO-66 metal organic frameworks with high contents of flexible adipic acid co-linkers.

Adipic acid, an industrially-important chemical that can be sustainably derived from biomass and post-consumer nylon, is traditionally overlooked as a linker for MOFs. Herein, we report the first direct one-pot method for synthesising UiO-66 MOFs with an unprecedented 69 mol% adipate content, as well as the feasibility of these materials for MOF defect engineering by rapid and selective adipate thermolysis.

Reactivity of Diamines in Acyclic Diamino Carbene Gold Complexes.

Acyclic diamino carbenes (ADCs) are interesting alternatives to their more widely studied N-heterocyclic carbene counterparts, particularly due to their greater synthetic accessibility and properties such as increased sigma donation and structural flexibility. ADC gold complexes are typically obtained through the reaction of equimolar amounts of primary/secondary amines on gold-coordinated isocyanide ligands. As such, the reaction of diamine nucleophiles to isocyanide gold complexes was expected to lead to bis-ADC gold compounds with potential applications in catalysis or as novel precursors for gold nanomaterials.

Metal-Organic Framework superstructures with long-ranged orientational order via E-field assisted liquid crystal assembly.

Most MOFs are non-cubic, with functionality dependent upon crystallographic direction, and are largely prepared as microcrystalline powders. Therefore, general methods to orient and assemble free-standing MOF crystals are especially important and urgently needed. This is addressed here through the novel strategy of E-field assisted liquid crystal assembly, applied to MIL-53-NH(Al), MIL-68(In) and NU-1000 MOF crystals, with aspect ratios ranging from 10 to 1.

Template-Controlled Synthesis of Polyimidazolium Salts by Multiple [2+2] Cycloaddition Reactions.

The tetrakisimidazolium salt H -2(Br) , featuring a central benzene linker and 1,2,4,5-(nBu-imidazolium-Ph-CH=CH-) substituents reacts with Ag O in the presence of AgBF to yield the tetranuclear, oktakis-NHC assembly [3](BF ) . Cation [3] features four pairs of olefins from the two tetrakis-NHC ligands perfectly arranged for a subsequent [2+2] cycloaddition. Irradiation of [3](BF ) with a high pressure Hg lamp connects the two tetra-NHC ligands through four cyclobutane linkers to give compound [4](BF ) .

Site-selective metallation of dicarbene precursors.

An imidazolium/2-chlorobenzimidazole bis-NHC precursor has been reacted with Ag2O followed by transmetallation with [AuCl(THT)] to give the Au-NHC complex via metallation of the imidazolium site, while the reaction of the same bis-NHC precursor with [Pd(PPh3)4] yields exclusively the azolato complex by oxidative addition of the C2-Cl bond to Pd0. Both complexes have been converted into the heterobimetallic Au/Pd-complex by reaction with [Pd(PPh)3]4 (for the NHC complex) or Ag2O/[AuCl(THT)] (for the azolato complex), respectively.

Template Synthesis of Three-Dimensional Hexakisimidazolium Cages.

A procedure for the synthesis of three-dimensional hexakisimidazolium cage compounds has been developed. The reaction of the trigonal trisimidazolium salts H L(PF ) , decorated with three N-olefinic pendants, and silver oxide yielded trinuclear trisilver(I) hexacarbene molecular cylinders of the type [Ag L ] with the olefinic pendants from the two different tricarbene ligands arranged in three pairs. Subsequent UV irradiation gave three cyclobutane links between the two tris-NHC ligands in three [2+2] cycloaddition reactions, thereby generating a three-dimensional hexakis-NHC ligand.

Imidazole-stabilized, electron-deficient boron cations.

The borenium cations [(CHNAd)B(CF)][AlCl/AlCl] 2a, and [(CHNMe)B(CF)][B(CF)] 2b were prepared and are shown to feature a high Lewis acidity, the capability to activate hydrogen and to effect the 1,1-carborations of terminal and internal alkynes under mild conditions.

High-Fidelity, Narcissistic Self-Sorting in the Synthesis of Organometallic Assemblies from Poly-NHC Ligands.

Highly selective, narcissistic self-sorting has been observed in the one-pot synthesis of three organometallic molecular cylinders of type [M {L-(NHC) } ](PF ) (M=Ag , Au ; L=1,3,5-benzene, triphenylamine, or 1,3,5-triphenylbenzene) from L-(NHC) and silver(I) or gold(I) ions. The molecular cylinders contain only one type of tris-NHC ligand with no crossover products detectable. Transmetalation of the tris-NHC ligands from Ag to Au in a one-pot reaction with retention of the supramolecular structures is also demonstrated.

Turn-On Fluorescence in Tetra-NHC Ligands by Rigidification through Metal Complexation: An Alternative to Aggregation-Induced Emission.

Two tetraphenylethylene (TPE) bridged tetraimidazolium salts, [H L-Et](PF ) and [H L-Bu](PF ) , were used as precursors for the synthesis of the dinuclear Ag and Au tetracarbene complexes [Ag (L-Et)](PF ) , [Ag (L-Bu)](PF ) , [Au (L-Et)](PF ) , and [Au (L-Bu)](PF ) . The tetraimidazolium salts show almost no fluorescence (Φ <1 %) in dilute solution while their NHC complexes display fluorescence "turn-on" (Φ up to 47 %). This can be ascribed to rigidification mediated by the restriction of intramolecular rotation within the TPE moiety upon complexation.

Tris(imidazolin-2-ylidenamino)phosphine: A Crystalline Phosphorus(III) Superbase That Splits Carbon Dioxide.

We report the synthesis and remarkable properties of the phosphine P(NIiPr) (NIiPr=1,3-diisopropyl-4,5-dimethylimidazolin-2-ylidenamino), a crystalline solid accessible through a short and scalable route. Evaluation of the electron-donor properties reveals a Tolman electronic parameter (TEP) value of 2029.7 cm for the new phosphine that is significantly lower than those of all known phosphines or even N-heterocyclic carbenes.

Synthesis of Complexes with Abnormal "Protic" N-Heterocyclic Carbenes.

Neutral 4-iodo-N-ethylimidazole 3 oxidatively adds to [Pt(PPh3)4] to give, in the presence of different tetraalkylammonium salts, complexes trans-[4], trans-[5], and trans-[6] containing an anionic C4-bound heterocycle with an unsubstituted ring-nitrogen atom. Complex trans-[4] reacts with the proton source NH4 I under protonation of the ring-nitrogen atom to produce complex trans-[7]I which bears an NH,NR-substituted aNHC ligand. The reaction of trans-[4] with CH3I yields the complex trans-[8]I which has a classical aNHC ligand with two alkylated ring-nitrogen atoms.

Motorized Janus metal organic framework crystals.

We describe Janus metal organic framework crystals that are propelled by bubble ejection. The Janus crystals are prepared by selective epitaxial growth of ZIF-67 on ZIF-8. The Janus crystals catalyse the decomposition of H2O2 into H2O and O2 on the ZIF-67 surface but not on the zinc containing ZIF-8 surface, resulting in propulsion of the Janus crystals.

Two-dimensional metal-organic framework with wide channels and responsive turn-on fluorescence for the chemical sensing of volatile organic compounds.

We report a 2D layered metal-organic framework (MOF) with wide channels named NUS-1 and its activated analogue NUS-1a composed of Zn4O-like secondary building units and tetraphenylethene (TPE)-based ligand 4,4'-(2,2-diphenylethene-1,1-diyl)dibenzoic acid. Due to its special structure, NUS-1a exhibits unprecedented gas sorption behavior, glass-transition-like phase transition under cryogenic conditions, and responsive turn-on fluorescence to various volatile organic compounds. Our approach using angular ligand containing partially fixed TPE units paves a way toward highly porous MOFs with fluorescence turn-on response that will find wide applications in chemical sensing.

Photoresponsive liquid marbles and dry water.

Stimuli-responsive liquid marbles for controlled release typically rely on organic moieties that require lengthy syntheses. We report herein a facile, one-step synthesis of hydrophobic and oleophobic TiO2 nanoparticles that display photoresponsive wettability. Water liquid marbles stabilized by these photoresponsive TiO2 particles were found to be stable when shielded from ultraviolet (UV) radiation; however, they quickly collapsed after being irradiated with 302 nm UV light.

Tuning omniphobicity via morphological control of metal-organic framework functionalized surfaces.

Fabrication of microstructures for imparting omniphobicity to a surface generally requires the use of lithographic techniques and specialized equipment. We report instead a simple strategy for the synthesis of microstructured surfaces via metal–organic framework (MOF) self-assembly. Our method allows us to localize epitaxial growth of MOF at the tips of needle crystals to create mushroom-shaped structures, thus conferring re-entrant textures to the MOF-functionalized surfaces.

Supergluing MOF liquid marbles.

Growth of NH(2)-MIL-53(Al) on alumina microparticles followed by post-synthetic modification with perfluorooctyl or caproic groups produces highly hydrophobic microparticles which are utilized for the formation of liquid marbles. Interfacial polymerization of ethyl-2-cyanoacrylate on the surface of the liquid marbles produces stable liquid capsules.