Design of an Organic Template for Synthesizing ITR Zeolites under Ge-Free Conditions.

Germanosilicate zeolites with various structures have been extensively synthesized, but the syntheses of corresponding zeolite structures in the absence of germanium species remain a challenge. One such example is an ITR zeolite structure, which is a twin of the ITH zeolite structure. Through the modification of a classic organic template for synthesizing ITH zeolites and thus designing a new organic template with high compatibility to ITR zeolite assisted by theoretical simulation, we, for the first time, show the Ge-free synthesis of an ITR structure including pure silica, aluminosilicate, and borosilicate ITR zeolites. These materials have high crystallinity, corresponding to an ITR content of more than 95%. In the methanol-to-propylene (MTP) reaction, the obtained aluminosilicate ITR zeolite exhibits excellent propylene selectivity and a long lifetime compared with conventional aluminosilicate ZSM-5 zeolite. The strategy for the design of organic templates might offer a new opportunity for rational syntheses of novel zeolites and, thus, the development of highly efficient zeolite catalysts in the future.

NMR Signatures and Electronic Structure of Ti Sites in Titanosilicalite-1 from Solid-State 47/49Ti NMR Spectroscopy.

Although titanosilicalite-1 (TS-1) is among the most successful oxidation catalysts used in industry, its active site structure is still debated. Recent efforts have mostly focused on understanding the role of defect sites and extraframework Ti. Here, we report the 47/49Ti signature of TS-1 and molecular analogues [Ti(OTBOS)4] and [Ti(OTBOS)3(OiPr)] using novel MAS CryoProbe to enhance the sensitivity. While the dehydrated TS-1 displays chemical shifts similar to those of molecular homologues, confirming the tetrahedral environment of Ti consistent with X-ray absorption spectroscopy, it is associated with a distribution of larger quadrupolar coupling constants, indicating an asymmetric environment. Detailed computational studies on cluster models highlights the high sensitivity of the NMR signatures (chemical shift and quadrupolar coupling constant) to small local structural changes. These calculations show that, while it will be difficult to distinguish mono- vs dinuclear sites, the sensitivity of the 47/49Ti NMR signature should enable distinguishing the Ti location among specific T site positions.

A Cationic Oligomer as an Organic Template for Direct Synthesis of Aluminosilicate ITH Zeolite.

There are a large number of zeolites, such as ITH, that cannot be prepared in the aluminosilicate form. Now, the successful synthesis of aluminosilicate ITH zeolite using a simple cationic oligomer as an organic template is presented. Key to the success is that the cationic oligomer has a strong complexation ability with aluminum species combined with a structural directing ability for the ITH structure similar to that of the conventional organic template. The aluminosilicate ITH zeolite has very high crystallinity, nanosheet-like crystal morphology, large surface area, fully four-coordinated Al species, and abundant acidic sites. Methanol-to-propylene (MTP) tests reveal that the Al-ITH zeolite shows much higher selectivity for propylene and longer lifetime than commercial ZSM-5. FCC tests show that Al-ITH zeolite is a good candidate as a shape-selective FCC additive for enhancing propylene and butylene selectivity.

Hidden diversity of vacancy networks in Prussian blue analogues.

Prussian blue analogues (PBAs) are a diverse family of microporous inorganic solids, known for their gas storage ability1, metal-ion immobilization2, proton conduction3, and stimuli-dependent magnetic4,5, electronic6 and optical7 properties. This family of materials includes the double-metal cyanide catalysts8,9 and the hexacyanoferrate/hexacyanomanganate battery materials10,11. Central to the various physical properties of PBAs is their ability to reversibly transport mass, a process enabled by structural vacancies. Conventionally presumed to be random12,13, vacancy arrangements are crucial because they control micropore-network characteristics, and hence the diffusivity and adsorption profiles14,15. The long-standing obstacle to characterizing the vacancy networks of PBAs is the inaccessibility of single crystals16. Here we report the growth of single crystals of various PBAs and the measurement and interpretation of their X-ray diffuse scattering patterns. We identify a diversity of non-random vacancy arrangements that is hidden from conventional crystallographic powder analysis. Moreover, we explain this unexpected phase complexity in terms of a simple microscopic model that is based on local rules of electroneutrality and centrosymmetry. The hidden phase boundaries that emerge demarcate vacancy-network polymorphs with very different micropore characteristics. Our results establish a foundation for correlated defect engineering in PBAs as a means of controlling storage capacity, anisotropy and transport efficiency.

Layered Zn2[Co(CN)6](CH3COO) double metal cyanide: a two-dimensional DMC phase with excellent catalytic performance.

Double metal cyanides (DMCs) are well known, industrially applied catalysts for ring opening polymerization reactions. In recent years, they have been studied for a variety of catalytic reactions, as well as other applications, such as energy storage and Cs sorption. Herein, a new, layered DMC phase (L-DMC), Zn2[Co(CN)6](CH3COO)·4H2O, was synthesized. The structure, which crystallizes in the monoclinic space group P21/m, consists of positively charged {Zn2Co(CN)6}+ DMC layers linked through acetate groups and presents a new layered structure to the family of double metal cyanides. L-DMC proved to be a reusable and stable catalyst that exhibited a higher activity than the benchmark DMC catalyst in two important applications: hydroamination of phenylacetylene with 4-isopropylaniline and polymerization of 1,2-epoxyhexane.

Metal ion exchange in Prussian blue analogues: Cu(ii)-exchanged Zn-Co PBAs as highly selective catalysts for A3 coupling.

The occurrence of metal ion exchange in Zn3[Co(CN)6]2 and Cu3[Co(CN)6]2 Prussian blue analogues (Zn-Co and Cu-Co PBAs) was demonstrated for the first time. While Cu(ii) ion exchange easily occurs in Zn-Co PBA, the exchange of Cu(ii) atoms in Cu-Co PBA by Zn(ii) proved to be more difficult. At low to medium Cu(ii) loadings, the catalytic activity of the exchanged PBAs for the A3 coupling reaction of benzaldehyde, piperidine and phenylacetylene was higher than that of the bimetallic PBAs and that of multi metal PBAs of similar composition prepared by co-precipitation. This result showcases the benefits of the ion exchange process as a preparation method of PBA catalysts, since it is believed to lead to the incorporation of the desired metal in a more accessible position for reactant molecules. At higher Cu(ii) loadings, ion exchange with Cu(CH3COO)2·H2O also resulted in co-incorporation of CH3COO-. This incorporation considerably boosted the catalytic activity of the PBAs by providing a basic function that facilitates the C-H activation of phenylacetylene. The most active of the studied PBAs, catallytically outperforms other Cu(ii) based A3 coupling catalysts and completely suppresses the activity for the homocoupling of phenylacetylene, even under oxidative conditions. Furthermore, the basicity of the PBAs was investigated in the nitroaldol (Henry) reaction, where a clear effect of the presence of CH3COO- was observed. The CH3COO- containing PBAs exhibited an activity three times higher than the rest of the PBAs. The presence of the basic CH3COO- groups represents the first case of basic functionalization of PBAs.

A Flexible Photoactive Titanium Metal-Organic Framework Based on a [Ti(IV)3(µ3-O)(O)2(COO)6] Cluster.

The synthesis of titanium-carboxylate metal-organic frameworks (MOFs) is hampered by the high reactivity of the commonly employed alkoxide precursors. Herein, we present an innovative approach to titanium-based MOFs by the use of titanocene dichloride to synthesize COK-69, the first breathing Ti MOF, which is built up from trans-1,4-cyclohexanedicarboxylate linkers and an unprecedented [Ti(IV)3(µ3-O)(O)2(COO)6] cluster. The photoactive properties of COK-69 were investigated in depth by proton-coupled electron-transfer experiments, which revealed that up to one Ti(IV) center per cluster can be photoreduced to Ti(III) while preserving the structural integrity of the framework. The electronic structure of COK-69 was determined by molecular modeling, and a band gap of 3.77 eV was found.

Bio-based nitriles from the heterogeneously catalyzed oxidative decarboxylation of amino acids.

The oxidative decarboxylation of amino acids to nitriles was achieved in aqueous solution by in situ halide oxidation using catalytic amounts of tungstate exchanged on a [Ni,Al] layered double hydroxide (LDH), NH4 Br, and H2 O2 as the terminal oxidant. Both halide oxidation and oxidative decarboxylation were facilitated by proximity effects between the reactants and the LDH catalyst. A wide range of amino acids was converted with high yields, often >90 %. The nitrile selectivity was excellent, and the system is compatible with amide, alcohol, and in particular carboxylic acid, amine, and guanidine functional groups after appropriate neutralization. This heterogeneous catalytic system was applied successfully to convert a protein-rich byproduct from the starch industry into useful bio-based N-containing chemicals.

New zeolite Al-COE-4: reaching highly shape-selective catalytic performance through interlayer expansion.

A ferrierite-type layered aluminosilicate, Al-RUB-36, was prepared for the first time and its interlayer expansion resulted in new zeolite catalysts denoted Al-COE-3 and Al-COE-4. Decane hydroconversion tests demonstrated the highly active and shape-selective nature of the new Al-COE-4 catalyst with an unprecedented isomerization yield, highlighting the potential of this material as a hydroisomerization catalyst. This is the first report on achieving shape-selectivity via interlayer expansion.