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Combining a cryogenic MAS probe and high magnetic field results in remarkable signal enhancement, permitting MOF characterization by 67Zn 3QMAS NMR at natural abundance.

The selective synthesis of the zinc-acetato-phosphinidene cluster [Zn6(μ3-PSiMe3)4(OAc)4(NC5H5)5] 1 is presented. The cluster serves as a stable, single-source precursor to yield soluble zinc phosphide nanoparticles via P–Si bond activation and AcOSiMe3 elimination when heated in oleylamine or other donor solvents.

Metal-organic frameworks (MOFs) are promising materials for carbon dioxide (CO2) adsorption and storage; however, many details regarding CO2 dynamics and specific adsorption site locations within MOFs remain unknown, restricting the practical uses of MOFs for CO2 capture. The intriguing α-magnesium formate (α-Mg3(HCOO)6) MOF can adsorb CO2 and features a small pore size. Using an intertwined approach of 13C solid-state NMR (SSNMR) spectroscopy, 1H-13C cross-polarization SSNMR, and computational molecular dynamics (MD) simulations, new physical insights and a rich variety of information have been uncovered regarding CO2 adsorption in this MOF, including the surprising suggestion that CO2 motion is restricted at elevated temperatures. Guest CO2 molecules undergo a combined localized rotational wobbling and non-localized twofold jumping between adsorption sites. MD simulations and SSNMR experiments accurately locate the CO2 adsorption sites; the mechanism behind CO2 adsorption is the distant interaction between the hydrogen atom of the MOF formate linker and a guest CO2 oxygen atom, which are ca. 3.2 A apart.

Microporous metal-organic frameworks (MOFs) have high surface areas and porosities, and are well-suited for CO2 capture. MIL-53 features corner-sharing MO4(OH)2 (M = Al, Ga, Cr, etc.) octahedra interconnected by benzenedicarboxylate linkers that form one-dimensional rhombic tunnels, and exhibits an excellent adsorption ability for guest molecules such as CO2. Studying the behavior of adsorbed CO2 in MIL-53 via solid-state NMR (SSNMR) provides rich information on the dynamic motion of guest molecules as well as their binding strengths to the MOF host, and sheds light on the specific guest adsorption mechanisms. Variable-temperature (13)C SSNMR spectra of (13)CO2 adsorbed within various forms of MIL-53 are acquired and analyzed. CO2 undergoes a combination of two motions within MIL-53; we report the types of motion present, their rates, and rotational angles. (1)H-(13)C CP SSNMR experiments are used to examine the proximity of (1)H atoms in the MOF to (13)C atoms in CO2 guests. By replacing (1)H with (2)H in MIL-53, the location of the CO2 adsorption site in MIL-53 is experimentally confirmed by (1)H-(13)C CP SSNMR. The binding strength of CO2 within these MIL-53 MOFs follows the order MIL-53-NH2 (Al) > MIL-53-NH2 (Ga) > MIL-53 (Al) > MIL-53 (Ga).

The solvent free reaction of Zn(OAc)2 with an imidazole ligand resulted in a 1-dimensional (1D) chain structure with the formula [Zn(Im)(HIm)2(OAc)] (Im = imidazolate, HIm = imidazole, OAc = carboxylate) (1). The results by kinetic experiments suggest that (1) likely evolves from an unidentified metastable phase. This new 1D chain precursor (1) is a quaternary system comprising Zn, Im, OAc and HIm. We have used this 1D compound as a single precursor to prepare 3-dimensional (3D) Zn(Im)2 frameworks. Specifically, two Zn(Im)2 frameworks with known zni and coi topologies were prepared via thermal-mediated transformation when heated in an open atmosphere and in a closed vessel, respectively. In an open atmosphere, the kinetic experiments confirmed the rapid phase transformation from (1) to zni without formation of an intermediate phase. In contrast, in the formation process of coi in a closed vessel, phase transformation from (1) to zni and immediately from zni to coi was observed. Thus, in a closed vessel, the released molecules, HOAc and HIm, were occluded in the framework, which may together exert a cooperative structure-directing effect on the formation of the coi framework. Thus, a single precursor approach was established for the synthesis of ZIFs. The present work represents the first example of transforming a 1D coordination polymer into 3D ZIF framework structures.

α-Magnesium formate [α-Mg3(HCOO)6], a representative lightweight Mg-based metal–organic framework (MOF), has the desirable properties of permanent porosity, unique stability and adsorption capacities for small molecules. Using in situ infrared (IR) and Raman spectroscopy, we investigated the structure and stability of the α-Mg3(HCOO)6 framework at high pressures up to 13 GPa. We found that the framework structure was chemically stable under compression, while an irreversible crystal-to-crystal structural transition was observed above 2 GPa. This new phase is likely isostructural with microporous γ-Mg3(HCOO)6. In contrast, the α-Mg3(HCOO)6 framework loaded with guest molecules such as dimethylformamide and benzene exhibits higher stability to external pressure. Neither a new crystalline phase nor an amorphous material was observed under pressure up to 13 GPa.

Formation of molecular sieve SAPO-34 has been examined under vapor-phase transport (VPT) conditions. Powder XRD, SEM/EDX, and solid-state NMR were used to follow the evolution of gel samples as a function of crystallization time. The results indicate that the initial VPT dry gel is a mixture of an amorphous material (major component) and a dense phase (minor component). The amorphous material is aluminophosphate in nature, but its structure is not suitable for transformation into SAPO-34 since it only has octahedral Al. Introducing morpholine (the structure directing agent) onto the surface of the dry gel via a vapor phase leads to changes in the structure of the amorphous phase as is evidenced by the conversion of octahedral Al into the tetrahedral Al sites. The dense phase is transformed into the tridymite phase. Upon further heating under VPT conditions, the equilibrium between tridymite and amorphous phases shifts to the amorphous material which is subsequently reorganized to form SAPO-34. The 29Si NMR results show that Si was incorporated into the framework at a later stage of crystallization via the formation of aluminosilicates. Catalytic tests indicate that the SAPO-34 product obtained by the VPT method had a longer lifetime for 100% methanol conversion and similar product selectivity to the SAPO-34 prepared by the normal hydrothermal synthesis.

We introduce a dip-coating method for preparing self-assembled monolayers (SAMs) of octadecylphosphonic acid (OPA) on hydrophilic substrates by selecting anisole (methoxybenzene) as the solvent, which has a dielectric constant of 4.3. We demonstrate that full-coverage OPA SAMs are formed in a couple of seconds on a cleaved mica substrate upon its dipping in a 1 mM OPA solution in anisole. In order to develop applications of this extremely rapid coating approach in surface engineering, we investigate the thermal stability of OPA SAMs dip-coated on a UV/ozone-cleaned aluminum film using water contact angle measurements and time-of-flight secondary ion mass spectrometry. It was clarified that the OPA SAMs annealed in air at up to 200 °C exhibited excellent hydrophobicity and the degradation mechanism is oxidation of the alkyl chains.

Here we report the structure and optical properties of a new Cu–cysteamine complex (Cu–Cy) with a formula of Cu3Cl(SR)2 (R = CH2CH2NH2). This Cu–Cy has a different structure from a previous Cu–Cy complex, in which both thio and amine groups from cysteamine bond with copper ions. Single-crystal X-ray diffraction and solid-state nuclear magnetic resonance results show that the oxidation state of copper in Cu3Cl(SR)2 is +1 rather than +2. Further, Cu3Cl(SR)2 has been observed to show intense photoluminescence and X-ray excited luminescence. More interesting is that Cu3Cl(SR)2 particles can produce singlet oxygen under irradiation by light or X-ray. This indicates that Cu3Cl(SR)2 is a new photosensitizer that can be used for deep cancer treatment as X-ray can penetrate soft tissues. All these findings mean that Cu3Cl(SR)2 is a new material with potential applications for lighting, radiation detection and cancer treatment.

Using a series of layered transition metal disulfides we demonstrate that the wide-line natural abundance solid-state NMR spectra of 33S in a less symmetric environment can readily be obtained at ultrahigh magnetic field of 21.1 T and that surprisingly these closely related materials display a wide range of 33S quadrupole coupling constant and chemical shift anisotropy values.

In this work, we present the effect of high external pressure on the structures of several representative zeolites: zeolite Y (Na-Y), lithium exchanged zeolite A (Li-A) and sodalite, as studied by IR spectroscopy. Pressure-induced amorphization was observed at 19 and 18 kbar in Na-Y and Li-A, respectively. However, the amorphous phases formed under such pressures seem to be reversible. The structural memory of the glasses might be due to the presence of hydrated charge balancing cations. Sodalite, on the other hand, exhibited no phase change in the pressure range of 0–48 kbar.

The order–disorder phase transition in 1,3-dimethyladamantane has been investigated by IR and Raman spectroscopy, and by proton spin–lattice relaxation time measurements, as functions of temperature. The splittings in the internal vibrational modes and number of lattice modes suggest that the structure of the ordered phase is either orthorhombic or monoclinic with at least two molecules per unit cell. Rotation of the methyl groups about their three-fold axes is responsible for relaxation in the ordered phase, and molecular tumbling occurs in the disordered phase. The barriers to molecular motion, determined from the spin–lattice relaxation times, are 14.3 and 15.8 kJ mol–1, respectively.

It is very difficult to selectively oxidise stable compounds such as toluene and xylenes to useful chemicals with molecular oxygen (O2) under moderate conditions. To achieve high conversion and less over-oxidised products, a new class of photocatalysts, metal hydroxide nanoparticles grafted with alcohols, is devised. They can efficiently oxidise alkyl aromatic compounds with O2 using visible or ultraviolet light or even sunlight to generate the corresponding aldehydes, alcohols and acids at ambient temperatures and give very little over-oxidation. For example toluene can be oxidised with a 23% conversion after a 48-hour exposure to sunlight with 85% of the product being benzaldehyde, and only a trace of CO2.The surface complexes grafted onto metal hydroxides can absorb light, generating free radicals on the surface, which then initiate aerobic oxidation of the stable alkyl aromatic molecules with high product selectivity. This mechanism is distinctly different from those of any known catalysts. The use of the new photocatalysts as a controlled means to generate surface radicals through light excitation allows us to drive the production of fine organic chemicals at ambient temperatures with sunlight. The process with the new photocatalysts is especially valuable for temperature-sensitive syntheses and a greener process than many conventional thermal reactions.

Protein nanogels were synthesized via a one-step reaction procedure by crosslinking urokinase with benzaldehyde bifunctionalized poly(ethylene glycol). The crosslinked architecture significantly enhances the stability of urokinase against enzyme degradation in comparison with the core–shell structural PEGylated proteins. Meanwhile, bioactivity of the urokinase incorporated in the nanogels can be adjusted by varying the chain length of the corsslinking polymer. With a shorter crosslinker the bioactivity of the uPA nanogels is seriously restricted under physiological conditions. However, the restricted bioactivity can be completely launched by either enlarging the mesh size of the nanogel by using longer crosslinkers, or treating the nanogels in endosomal conditions to dissociate the nanogel structure due to the reversible conjugation chemistry.

ZIF-8 as a promising storage material was investigated at high pressures up to ~39 GPa by in situ FTIR spectroscopy for the first time. Structural modifications are found to be reversible in a low-pressure region but irreversible in a high-pressure region. Overall, the ZIF-8 framework exhibits an unusual chemical stability even under extreme compression.

The grafting of optimal trace silica on TiO2 (anatase) substrates possessing a large specific surface area can significantly enhance their photocatalytic activity for decomposing organic contaminants, such as chlorophenols and phenol in water under visible-light illumination. The silica grafting produces surface electronic states within the TiO2 band gap, which are responsible for the visible-light activity. Different from the bulk doping, SiO2 was grafted on the anatase surface in two possible modes: (i) formation of SiO2 clusters on the surface; and (ii) substitution of Si atoms for Ti atoms of the outmost layer at the surface. Thus, the surface electronic states originate mainly from the 2p orbitals of coordination-unsaturated oxygen atoms bound to Si atoms. The location of these states depends on the forms by which the introduced silica species exist and the type of the grafted facet. Nonetheless, the attempt of grafting the same substrate with alumina failed. Also a greater enhancement in the visible-light activity was achieved when TiO2 surfaces with higher surface energy, such as the surfaces of anatase (010) and (116) planes, were grafted. Advantages of the grafted approach include: (i) different from bulk-doping, the surface-grafting does not change the crystalline and electronic structure in the bulk of the photocatalysts; (ii) and consequently the electron mobility in the photocatalysts and their photocatalytic activity under UV irradiation are not affected, (iii) the grafted photocatalysts have high chemical stability and repeatable photocatalytic activity.

This work examines the formation of a microporous gallophosphate with an extra large pore system, namely cloverite (structure type: CLO) in fluoride medium. The amorphous gallophosphate gel containing the key precursor to cloverite was characterized and its evolution followed by 31P, 71Ga, 19F and 1H MAS NMR and several dipolar-coupling based double-resonance methods including 31P{71Ga} and 19F{71Ga} rotational-echo adiabatic passage double-resonance (REAPDOR), 31P{19F} and 19F{31P} rotational-echo double-resonance (REDOR), and 1H{31P} REDOR and 1H{71Ga} transfer of populations in double-resonance (TRAPDOR). The results indicate that upon mixing the Ga and P sources in the presence of structure directing agent (SDA) and HF, an amorphous oxyfluorinated gallophosphate precursor containing single 4-rings (4Rs) with alternating Ga–O–P linkage forms immediately. The Ga in the 4R is 6-coordinated and the two Ga in the 4R are bridged by a fluorine. Heating quickly converts the 4Rs to double four-membered rings (D4Rs), from which the entire CLO structure is built. The amount of the D4R rapidly increases with increasing heating time. The presence of fluoride ions greatly facilitates the formation of the 4Rs via bridging two Ga sites and the hydrothermal treatment promotes D4Rs via condensation. Interaction between SDA molecule and the phosphorus site in the gel is also probed. Further, the local structure of Ga sites in cloverite is characterized by 71Ga MAS NMR at ultrahigh magnetic field of 21.1 T by obtaining their electric field gradient tensor parameters.

Hexagonally ordered mesoporous MCM-41 with 3 nm pores has been impregnated with the metal chalcogenolate Cu6- (TePh)6(PPh2Et)5 1: the analysis and condensation of this material is a step toward the synthesis of semiconducting nanowires.

Highly proton conductive silicas with phosphonic acid functionalization were synthesized by co-condensation of diethylphosphatoethyltriethoxysilane (DPTS) and tetraethoxysilane in a sol-gel process, followed by acidification of the phosphonate groups. These functionalized silicas with various phosphonic acid contents were extensively characterized to examine their structures and properties; in particular their intermediate temperature proton conductivity at 100–150 °C were systematically investigated under a variety of relative humidity (RH) conditions. The prepared samples have a mesoporous or nonporous structure depending on the DPTS amount used in the synthesis, and show high thermal stability under inert and oxidative atmospheres. We found that the present silicas still exhibit water-dependent proton conduction, but their conductivity under low humidity conditions has been significantly enhanced by up to two orders of magnitude compared to those phosphonic acid functionalized silicas previously reported. Herein, the highest conductivity has been obtained at 150 °C ranging from 4.4 × 10−4 S cm−1 at 20% RH to 0.031 S cm−1 at 100% RH. In general, proton conductivity is largely influenced by the content of phosphonic acid and the porous structure of the materials. Notably, the uniform mesostructure with a high surface area was found to greatly improve the proton conductivity at low humidity. The vehicle mechanism dominates the proton conduction at high humidity, whereas the conductivity at low humidity is likely a consequence of the structure diffusion (the Grotthuss mechanism). In addition, these materials are insoluble in water, rendering a practical suitability for fuel cell applications.

X-ray diffraction patterns of hydrated Na-X zeolite at 1 atm and 22 °C, recovered from high pressure experiments at pressures up to 9 GPa, showed progressive amorphization with increasing pressure. The largest reduction in crystallinity is observed between pressures of 4 and 5 GPa followed by a gradual, continued decrease in ordering up to the maximum pressure. The last vestiges of crystal structure persist to 8 GPa but the sample is completely amorphous at 9 GPa. Heating to 873 K in a differential scanning calorimetry (DSC) apparatus after decompression showed a shift in the broad dehydration endotherm to lower temperatures and a decrease in the endotherm width with increasing pressure. Follow-up X-ray patterns at 1 atm and 295 K after heating showed significant changes in peak intensities and width of the amorphous background signature. These observations are consistent with the negative thermal expansion of Na-X zeolite which results in further compression of the remnant lattice on heating.

The 13C cross-polarization magic angle spinning NMR spectra of crystalline Zeise's salt, K[PtCl3(η2-C2H4)], and Zeise's dimer, trans-[{PtCl2(η2-C2H4)}2], have been recorded at room temperature. The 13C chemical shift tensors have been determined. The values of the tensor elements are compared to those of the free ethylene ligand and are discussed in terms of the bonding.