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In this work, we evaluate the electrochemical properties of MBH4-C60 (M = Li+, Na+) nanocomposites for potential use as a solid-state electrolyte in alkali-ion batteries. The enhancement of ionic conductivity for MBH4 was achieved through the addition of C60 and partial dehydrogenation, resulting in an electrolyte with significantly higher ionic conductivity when compared to the pure MBH4. This improvement is attributed to the nanoionic destabilization of the MBH4 salt due to the affinity of the BH4− anion for C60 and partial dehydrogenation of the MBH4 through heating. The LiBH4-C60 nanocomposite was successfully paired with two anodes (graphite and lithium titanate) and two cathodes (LiFePO4 and TiS2) and galvanostatically cycled. The NaBH4-C60 nanocomposite showed nearly a 4-order-of-magnitude increase in ionic conductivity versus pure NaBH4 and demonstrated reversible sodium stripping and plating in a symmetric cell.

Faujasite (FAU) zeolites (with Si/Al ratio of ca. 1.7) undergo mild dealumination at moderate ion exchange conditions (0.01 to 0.6 M of NH 4 NO 3 solutions) resulting in protons circumscribed by sodalite cages becoming accessible for reaction without conspicuous changes to bulk crystallinity. The ratio of protons in sodalite cages (H SOD ) to supercages (H SUP ) can be systematically manipulated from 0 to ca. 1 by adjusting ammonium concentrations used in ion exchange. The fraction of accessible protons in the sodalite cages is assessed by virtue of infrared spectra for H-D exchange of deuterated propane based on the band area ratio of OD 2620 / OD 2680 (OD SOD / OD SUP ). Protons in sodalite cages (H SOD ) show higher rate constants of propane dehydrogenation ( k D ) and cracking ( k C ) than protons in supercages (H SUP ) plausibly due to confinement effects being more prominent in smaller voids. Rate constants of dehydrogenation and cracking including k D / k C ratios are also augmented as the fraction of accessible protons in the sodalite cages is enhanced. These effects of accessibility and reactivity of protons in sodalite cages hitherto inconspicuous are revealed herein via methods that systematically increase accessibility of cations located in sodalite cages.

We investigated the substitution of structure-directing agent diisobutylimidazolium hydroxide with cetyltrimethylammonium hydroxide (CTA+OH−) surfactant in the synthesis gel of layered-zeotype-precursor B-SSZ-70(P). At low substitution levels, CTA+ interacts with the external-zeotype surface, where it assembles. At higher surfactant amounts, CTA+ intercalation occurs, leading to swelling of the precursor material, as evidenced by powder X-ray diffraction. Characterization of adsorbed CTA+ cations by 13C MAS NMR spectroscopy demonstrates unique broad resonances in the intercalated layers, which represent a more rigid environment than in the external-surface assemblies. At still higher CTA+ substitution levels in the synthesis gel, we observe the formation of amorphous mesoporous silica. We attempted to delaminate materials synthesized with varying CTA+ substitution levels using mild conditions, in which the conventional sonication step is replaced with an easy-to-scale high-shear mixing, and in which the use of halide reagents, which are corrosive and have been required in the past, is also avoided. Our data demonstrate that synthesis of a swollen material per se is not essential as an intermediate for delamination, and that layered zeolite precursor swelling can actually undermine zeolite delamination. Our results instead point to the CTA+ external-surface assemblies as facilitating ease of SSZ-70 delamination under these mild conditions. When calcined and functionalized with grafted titanium centers, the delaminated materials are highly active and selective olefin epoxidation catalysts with organic hydroperoxides, showing a 40% higher epoxide conversion than a catalyst prepared from conventional B-SSZ-70.

In this contribution, we extend some of the explorations in using ionic liquids as both solution media and organic–guest contributors to the eventual crystallizing structure, when attempts are made synthesize MAPO molecular sieves. We synthesize a family of imidazolium bromides for this purpose and demonstrated a trend toward increasing substituent length on the nitrogen sites. These materials are run as reaction systems using 5 inorganic situations: metals Ni, Zn, Co and Mg substituting in part for Al, and then a 5th reaction where there is no metal added. A variety of MAPO products are made and there are some correlati ons for the size of the imidazolium guest and the internal void space of the microporous material. Further analysis of some of the details of the products was carried out using solid state MAS NMR and focusing on Al, P and F nuclei in the products. There are some interesting observations found as to deviation from simple tetrahedral coordination for the Al and P, depending upon the imidazolium guest and the metal incorporated. Then, more attention was also focused on the reactions for Ni where once the guests became large enough the products seemed to be the 12-ring structure AFI which has parallel one dimensional pores. It seemed to be that the Ni is not able to be part of the lattice in these instances, and in fact, AFI is the product for a variety of the larger imidazolium guest molecules in the reaction run without any metal added for substitution.

The structural changes underlying the deactivation of Sn-Beta zeolites under aqueous-phase reaction conditions at elevated temperatures (373 K) are investigated using spectroscopic characterization and site titration techniques together with turnover rates for glucose isomerization, a well-understood probe reaction for which changes in measured rates can be ascribed to specific changes in catalyst structure. In the case of hydrophobic, low-defect Sn-Beta zeolites (Sn-Beta-F), treatment in hot liquid water (373 K) for short times (3 h) to hot liquid water causes turnover rates to decrease and approach values characteristic of hydrophilic, defect-rich Sn-Beta zeolites (Sn-Beta-OH). In contrast, turnover rates on hydrophilic Sn-Beta-OH zeolites are insensitive to the duration of hot liquid water exposure prior to reaction. Activation and deactivation phenomena on Sn-Beta-F zeolites occur concomitantly with the formation of silanol defects (by ∼2–10×) with increasing durations (0–24 h) of hot water treatment, despite negligible differences in open and closed Sn site speciation as quantified ex situ by CD_3CN IR spectra. Mechanistic interpretations of these phenomena suggest that silanol groups present at low densities serve as binding sites for water molecules and clusters, which confer enthalpic stability to kinetically-relevant hydride-shift transition states and increase turnover rates, while silanol groups present in higher densities stabilize extended hydrogen-bonded water networks, which entropically destabilize kinetically-relevant transition states and decrease turnover rates. Intraporous voids within hydrophobic Sn-Beta-F zeolites become increasingly hydrophilic as silanol groups are formed by hydrolysis of framework siloxane bridges with increasing durations of water treatment, thereby decreasing aqueous-phase glucose isomerization turnover rates (per open Sn site). These findings suggest design strategies that suppress framework hydrolysis would attenuate the deactivation of Lewis acid zeolites in aqueous media.

Aqueous amines are currently the most promising solution for large-scale CO_2 capture from industrial sources. However, molecular design and optimization of amine-based solvents have proceeded slowly due to a lack of understanding of the underlying reaction mechanisms. Unique and unexpected reaction mechanisms involved in CO_2 absorption into aqueous hydrazine are identified using ^1H, ^(13)C, and ^(15)N NMR spectroscopy combined with first-principles quantum-mechanical simulations. We find production of both hydrazine mono-carbamate (NH_2-NH-COO^−) and hydrazine di-carbamate (^−OOC-NH-NH-COO^−), with the latter becoming more populated with increasing CO_2 loading. Exchange NMR spectroscopy also demonstrates that the reaction products are in dynamic equilibrium under ambient conditions due to CO_2 exchange between mono-carbamate and di-carbamate as well as fast proton transfer between un-protonated free hydrazine and mono-carbamate. The exchange rate rises steeply at high CO_2 loadings, enhancing CO_2 release, which appears to be a unique property of hydrazine in aqueous solution. The underlying mechanisms of these processes are further evaluated using quantum mechanical calculations. We also analyze and discuss reversible precipitation of carbamate and conversion of bicarbonate to carbamates. The comprehensive mechanistic study provides useful guidance for optimal design of amine-based solvents and processes to reduce the cost of carbon capture. Moreover, this work demonstrates the value of a combined experimental and computational approach for exploring the complex reaction dynamics of CO_2 in aqueous amines.

A study exploring the use of ionic liquid reactions based on imidazolium halides in molecular sieve synthesis has produced a novel zincoaluminophosphate material with an open DFO-type framework structure. This framework structure had only been observed previously in the magnesioaluminophosphate system (Mg-DAF-1) where decamethonium was used as the structure directing agent. The new Zn-DAF-1 material has been characterized using chemical and thermogravimetric analysis and ^(13)C, ^(19)F, ^(27)Al and ^(31)P MAS NMR techniques. Structure analysis (P6/mcc, a = 22.2244(1) Å, c = 42.3293(3) Å) using synchrotron powder diffraction data not only confirmed the framework structure, but also revealed the locations of the Al, P and Zn atoms in the framework, the N,N′-di-isopropyl-imidazolium (DIPI) ions in the pores, some fluoride ions associated with double 4-rings, and some water molecules and anions filling the remaining space. This level of structural detail had not been possible in the Mg-DAF-1 material. Four different locations for the DIPI cation were found in the two 12-ring channels and Zn was found to substitute for only one of the six crystallographically distinct Al sites to yield the approximate crystal chemical formula |(DIPI)_(17)(OH,F)_(11)(H2O)_(23)|[Zn_6Al_(126)P_(132)O_(528)]-DFO.

Understanding of surface interactions between borohydride molecules and the surfaces of porous supports have gained growing attention for successful development of nano-confinement engineering. By use of in␣situ variable temperature (VT) magic angle spinning (MAS) NMR, molecular mobility changes of LiBH_4 crystalline solid has been investigated in the presence of silica based and carbonaceous surfaces. Spin–spin J-coupling of ^(1)H–^(11)B in LiBH_4 was monitored in series of VT NMR spectra to probe translational mobility of LiBH_4 that appeared to be greatly enhanced upon surface contact. Such enhanced diffusivity was found to be effective in the formation of solid solution and co-confinement with other metal borohydrides. Co-confinement of LiBH_4–Ca(BH_4)_2 mixture was demonstrated at temperature as low as 100 °C, much lower than the reported bulk eutectic melting temperature. The discovery adds a novel property of LiBH_4 that has been proven to be highly versatile in many energy related applications.

Generation of fluidic LiBH_4 molecules, ƒ-LiBH_4, was demonstrated by NMR spectroscopy of LiBH_4 bulk powder mixed with silica scaffold surface materials under minor heat treatment. In the presence of the fumed silica or mesoporous MCM-41 and SBA-15, LiBH_4 shows increased translational mobility at relatively low temperature (ca. 95 °C) and becomes liquid-like by evidence from ^1H–^(11)B J-coupling in ^1H and ^(11)B MAS NMR or substantial line narrowing of ^7Li static NMR. This high diffusional mobility of LiBH_4 at the molecular level has never been seen for bulk LiBH_4, and the property is attributed to the interfacial interaction with the mesoporous scaffold surfaces. While ƒ-LiBH_4 facilitates the confinement of LiBH_4 itself into various scaffold materials, LiBH_4 migrates along the SBA-15 surface to reach other metal borohydride particles, Ca(BH_4)_2 in this case, and promotes the formation of similarly fluidic LiBH_4–Ca(BH_4)_2 composite (LC solid solution) for coconfinement into mesopores. In situ variable temperature (VT) NMR spectroscopy detects the co-infiltration process of eutectic LiBH_4–Ca(BH_4)_2 composite (LC) into mesopores of SBA-15. The infiltration rates measured for LiBH_4 bulk powder or LC composite showed dependence on pore sizes (MCM-41 vs SBA-15) and heat treatment conditions (static vs MAS).

High resolution, multi-nuclear solid state nuclear magnetic resonance (NMR) characterizations are carried out in order to obtain insights into the structural features of Sn-beta zeolites that catalyze glucose isomerization or epimerization reactions in water and methanol solvents. In particular, we focus on investigating the local structural changes to catalytically-active framework Sn sites of different ^(119)Sn-labeled beta zeolites, including the calcined, dehydrated, rehydrated, and post-sugar isomerization catalysis forms. Magic angle spinning (MAS) and cross polarization MAS (either from ^1H or ^(19)F) ^(119)Sn NMR spectra provide evidence for changes to the local framework Sn coordination in the presence of water and sugar molecules, and provide insights into structural features of adsorbed intermediates that may be relevant in sugar isomerization reaction pathways.

Delaminated zeolite UCB-3 exhibits 2.4-fold greater catalytic activity relative to its three-dimensional (3D) zeolite counterpart, Al-SSZ-70, and 2.0-fold greater activity (per catalyst mass) when compared with industrial catalyst MCM-22, for the alkylation of toluene with propylene at 523 K. The former increase is nearly equal to the observed relative increase in external surface area and acid sites upon delamination. However, at 423 K for the same reaction, UCB-3 exhibits a 3.5-fold greater catalytic activity relative to 3D Al-SSZ-70. The higher relative rate enhancement for the delaminated material at lower temperature can be elucidated on the basis of increased contributions from internal acid sites. Evidence of possible contributions from such acid sites is obtained by performing catalysis after silanation treatment, which demonstrates that although virtually all catalysis in MCM-22 occurs on the external surface, catalysis also occurs on internal sites for 3D Al-SSZ-70. The additional observed enhancement at low temperatures can therefore be rationalized by greater access to internal active sites as a result of sheet breakage during delamination. Such breakage leads to shorter characteristic internal diffusion paths and was visualized using TEM comparisons of UCB-3 and 3D Al-SSZ-70.

Framework Lewis acidic tin sites in hydrophobic, pure-silica molecular sieves with the zeolite beta topology (Sn-Beta) have been reported previously to predominantly catalyze glucose−fructose isomerization via 1,2 intramolecular hydride shift in water and glucose–mannose epimerization via 1,2 intramolecular carbon shift in methanol. Here, we show that alkali-free Sn-Beta predominantly isomerizes glucose to fructose via 1,2 intramolecular hydride shift in both water and methanol. Increasing extents of postsynthetic Na+ exchange onto Sn-Beta, however, progressively shifts the reaction pathway toward glucose–mannose epimerization via 1,2 intramolecular carbon shift. Na^+ remains exchanged onto silanol groups proximal to Sn centers during reaction in methanol solvent, leading to nearly exclusive selectivity toward epimerization. In contrast, decationation occurs with increasing reaction time in aqueous solvent and gradually shifts the reaction selectivity to isomerization at the expense of epimerization. Decationation and the concomitant selectivity changes are mitigated by the addition of NaCl to the aqueous reaction solution. Preadsorption of ammonia onto Sn-Beta leads to near complete suppression of infrared and ^(119)Sn nuclear magnetic resonance spectroscopic signatures attributed to open Sn sites and of glucose−fructose isomerization pathways in water and methanol. These data provide evidence that Lewis acidic open Sn sites with either proximal silanol groups or Na-exchanged silanol groups are respectively the active sites for glucose–fructose isomerization and glucose–mannose epimerization.

The recent discovery of a new class of negative ions called hyperhalogens allows us to characterize this complex as belonging to a unique class of materials called hypersalts. Hyperhalogen materials are important while serving as the building blocks for the development of new materials having enhanced magnetic or oxidative properties. One prime example of a hydperhalogen is the Al(BH_4)_4^– anion. Aluminum borohydride (17 wt % H) in itself is a volatile, pyrophoric compound that has a tendency to release diborane at room temperature, making its handling difficult and very undesirable for use in practical applications. Here we report that the combination of Al(BH_4)_3 with the alkaline metal borohydride KBH_4 results in the formation of a new compound KAl(BH_4)_4 which is a white solid that exhibits remarkable thermal stability up to 154 °C and has the typical makeup of a hypersalt material. Using a variety of characterization tools and theoretical calculations, we study and analyze the physical characteristics of this compound and show its potential for stabilizing high hydrogen capacity, energetic materials.

The effect of calixarene ligand symmetry, as dictated by lower-rim substitution pattern, on the coordination to a Ti(IV) cation is assessed in solution and when grafted on SiO_2, and its effect on epoxidation catalysis by Ti(IV)-calixarene grafted on SiO_2 is investigated. C_(2v) symmetric Ti-tert-butylcalix[4]arene complexes that are 1,3-alkyl disubstituted at the lower rim (di-R-Ti) are compared to previously reported grafted C_s symmetric complexes, which are singly substituted at the lower rim (mono-R-Ti). ^(13)C MAS NMR spectra of complexes isotopically enriched at the lower-rim alkyl position indicate that di-R-Ti predominantly grafts onto silica as the conformation found in solution, exhibiting a deshielded alkyl resonance compared to the grafted mono-R-Ti complexes, which is consistent with stronger alkyl ether→Ti dative interactions that are hypothesized to result in higher electron density at the Ti center. Moreover, ^(13)C MAS NMR spectroscopy detects an additional contribution from an “endo” conformer for grafted di-R-Ti sites, which is not observed in solution. Based on prior molecular modeling studies and on ^(13)C MAS NMR spectroscopy chemical shifts, this “endo” conformer is proposed to have similar Ti–(alkyl ether) distances at the lower-rim and electron density at the Ti center relative to grafted mono-R-Ti complexes. Differences between grafted mono-R-Ti and di-R-Ti sites can be observed by ligand-to-metal charge transfer edge-energies, calculated from diffuse-reflectance UV–visible spectroscopy at 2.24 ± 0.02 and 2.16 ± 0.02 eV, respectively. However, rates of tert-butyl hydroperoxide consumption in the epoxidation of 1-octene are found to be largely unchanged when compared to those of the grafted mono-R-Ti complexes, with average rate constants of ~1.5 M^(−2) s^(−1) and initial TOF of ~4 ks^(−1) at 323 K. This suggests that an “endo” conformation of grafted di-R-Ti may prevail during catalysis. Despite this, grafted di-C_1-Ti complexes can be more selective than mono-C_1-Ti complexes (45 vs. 34 % at a 50 % conversion at 338 and 353 K), illustrating the importance of the Ti coordination environment on epoxidation catalysis.

Alteration of the thermodynamic stability of selected borohydride/alanate systems, including the combination of LiBH_4 with NaAlH_4 and LiBH_4 with CaCl_2 and LiAlH_4, was investigated to determine the possibility of forming intermediate stability mixed AlH_(4)^(−)–BH_(4)^(−) phase. Facile metathesis exchange reactions were observed when NaAlH_4 was combined with LiBH_4 resulting in the formation of LiAlH_4 and NaBH_4. Thermal analysis of this system showed that the 1st and 2nd decomposition of LiAlH_4 occurred irrespective of NaBH_4 illustrating the absence molecular level interaction between the AlH_(4)^(−) and the BH_(4)^(−) anions. On the other hand, in the case of CaCl_2, LiAlH_4, LiBH_4 combination, the results showed the formation of a calcium alanate type phase. Evaluation of the thermal property of this system showed an endothermic one step decomposition between 130 °C and 200 °C (2.3 wt% loss). Structural examination of this calcium alanate type phase revealed a different local coordination geometry of AlH_(4)^(−) from that observed in calcium alanate. The formation and properties of this phase are being attributed to molecular level AlH_(4)^(−)–BH_(4)^(−) interactions. These findings provide a pathway toward designing novel alanates-borohydrides systems for hydrogen storage applications. This article will show the methodologies followed and explain the results obtained.

A synthetic route to borosilicate zeolites is described which yields relatively boron-rich products. The reaction takes place under high reactant concentrations and utilizes fluoride delivered as the ammonium fluoride salt rather than as hydrofluoric acid. The reaction is an adaptation of the conditions (HF) initially used to discover zeolite SSZ-70. Exploring a range of structure-directing agents (SDA), several boron-rich phases crystallized. Reactions are generally quite slow, however. A more in-depth study with an adamantyl SDA finds zeolite SSZ-23 favored over SSZ-13. Multinuclear NMR experiments were carried out to better understand the boron substitution in SSZ-23 and to probe if there are key B–F interactions in its formation. Finally, providing alkali cation sources of fluoride shifts the product selectivity away from SSZ-23 and back toward SSZ-13.

In Part 1, the promising hydrogen storage properties of the combined systems of Li3AlH6/LiBH4 and Al/LiBH4, exhibiting the favorable formation of AlB2 during dehydrogenation, were presented based on TGA and XRD analyses. The present Part 2 describes the characterization of the intermediate and final products of the dehydrogenation and rehydrogenation of the above systems by multinuclear solid-state NMR characterization. This work has also verified that the presence of Al resulted in the re-formation of LiBH4 occurring at a much lower temperature and H2 pressure, under which conditions the dehydrogenation product from LiBH4 alone does not show any degree of rehydrogenation. NMR studies mainly identified various reaction intermediates for LiBH4 dehydrogenation/rehydrogenation reactions. Unlike the XRD studies, the AlB2 formation, in particular, could not be unambiguously confirmed by NMR. 27Al NMR showed that aluminum was mainly involved in various Li—Al alloy formations. The catalytic role of Al in the LiB...

An unusual case of a diquaternary ammonium dication, with large bulky end groups built from the tropane moiety and connected by a C4 methylene chain, is found to reside in zeolite SSZ-35 (STF). The structure of the guest/host product is such that the tropane bicylic entities reside in the shallow cavities of the cages of the STF structure and the C4 methylene chain runs through the 10-ring (~5.5 Å) window that connects the cages. This is a most unusual (and energy-intensive) templating of a zeolite structure with the guest molecule spanning two unit cells. The unusual result was found by single crystal studies with the addition of the use of the SQUEEZE program to show a consistent fit for the guest molecule following from measured electron densities in the crystal structure work. These analyses were followed with MAS NMR studies to confirm the integrity of the diquaternary guest molecule in the host sieve. A few comparative diquaternary guest molecules in MFI zeolite are also studied.

By in situ X-ray diffraction (XRD) and nuclear magnetic resonance (NMR) spectroscopy, the role of Li2B12H12 for the sorption of LiBH4 is analyzed. We demonstrate that Li2B12H12 and an amorphous Li2B10H10 phase are formed by the reaction of LiBH4 with diborane (B2H6) at 200 °C. Based on our present results, we propose that the Li2B12H12 formation in the desorption of LiBH4 can be explained as a result of reaction of diborane and LiBH4. This reaction of the borohydride with diborane may also be observed for other borohydrides, where B12H12 phases are found during decomposition.

Desorption and subsequent rehydrogenation of Mg(BH_4)_2 with and without 5 mol % TiF_3 and ScCl_3 have been investigated. Temperature programmed desorption (TPD) experiments revealed a significant increase in the rate of desorption as well as the weight percentage of hydrogen released with additives upon heating to 300 °C. Stable Mg(B_xH_y)_n intermediates were formed at 300 °C, whereas MgB_2 was the major product when heated to 600 °C. These samples were then rehydrogenated and subsequently characterized with powder X-ray diffraction (pXRD), Raman, and NMR spectroscopy. We confirmed significant conversion of MgB_2 to fully hydrogenated Mg(BH_4)_2 for the sample with and without additives. TPD and NMR studies revealed that the additives have a significant effect on the reaction pathway during both dehydrogenation and rehydrogenation reactions. This work suggests that the use of additives may provide a valid pathway for improving intrinsic hydrogen storage properties of magnesium borohydride.

A lithium salt of anionic scandium tetraborohydride complex, LiSc(BH_4)_4, was studied both experimentally and theoretically as a potential hydrogen storage medium. Ball milling mixtures of LiBH_4 and ScCl_3 produced LiCl and a unique crystalline hydride, which has been unequivocally identified via multinuclear solid-state nuclear magnetic resonance (NMR) to be LiSc(BH_4)_4. Under the present reaction conditions, there was no evidence for the formation of binary Sc(BH_4)_3. These observations are in agreement with our first-principles calculations of the relative stabilities of these phases. A tetragonal structure in space group I (#82) is predicted to be the lowest energy state for LiSc(BH_4)_4, which does not correspond to structures obtained to date on the crystalline ternary borohydride phases made by ball milling. Perhaps reaction conditions are resulting in formation of other polymorphs, which should be investigated in future studies via neutron scattering on deuterides. Hydrogen desorption while heating these Li−Sc−B−H materials up to 400 °C yielded only amorphous phases (besides the virtually unchanged LiCl) that were determined by NMR to be primarily ScB_2 and [B_(12)H_(12)]^(−2) anion containing (e.g., Li_2B_(12)H_(12)) along with residual LiBH_4. Reaction of a desorbed LiSc(BH_4)_4 + 4LiCl mixture (from 4LiBH_4/ScCl_3 sample) with hydrogen gas at 70 bar resulted only in an increase in the contents of Li_2B_(12)H_(12) and LiBH_4. Full reversibility to reform the LiSc(BH_4)_4 was not found. Overall, the Li−Sc−B−H system is not a favorable candidate for hydrogen storage applications.

An additional dimension has been added to our long-standing studies in high silica zeolite synthesis via a guest/host synergism. We have created and studied the impact of making symmetric diquaternary ammonium compounds, by varying the chain length between nitrogen charge centers, and the heterocycle size and geometry containing the nitrogen. This allows the introduction of a second spatial parameter in the use of the charged organo-cation guest in the zeolite synthesis. The series of 15 diquaternary ammonium compounds (5 heterocycles synthesized onto chain lengths of C4-C6) were tested in a total of 135 zeolite syntheses reactions. Nine screening reactions were employed for each guest molecule, and the conditions built upon past successes in finding novel high silica zeolites via introduction of boron, aluminum, or germanium as substituting tetrahedral framework atoms for silicon. Eighteen different zeolite structures emerged from the studies. The use of specific chain lengths for derivatives of the pyrrolidine ring system produced novel zeolite materials SSZ-74 and 75.

The decomposition of crystalline magnesium borohydride upon heating was studied using thermal desorption, calorimetry, in situ X-ray diffraction, and solid state NMR. Hydrogen release from Mg(BH4)2 occurs in at least four steps via formation of several polyborane intermediate species and includes an exothermic reaction yielding crystalline MgH2 as an intermediate. The decomposition products may be only partially recharged after the very first step and also via hydrogenation of Mg metal. The intermediate formation of amorphous MgB12H12, was confirmed by 11B NMR. A four-stage pathway for the thermal decomposition of Mg(BH4)2 is proposed.

Reversible dehydrogenation and hydrogenation reactions have been reported for a number of reactions based on lithium alanate and lithium amide materials. The dehydrogenation and hydrogenation reactions involving these materials are, however, usually very complex. Significant discrepancies exist among different studies published in literature. Understanding the reaction mechanism and the dependence of the reaction pathway on material preparation processes and processing parameters is critical. In this paper, the hydrogenation reactions of the mixture of 3Li2NH/Al/4 wt%TiCl3 were investigated as a function of the heating rate. The hydrogenated products were characterized by means of TGA, XRD and solid-state NMR. These new results showed that the re-formation of Li3AlH6 depends strongly on the heating rate during the hydrogenation process. The dehydrogenation and rehydrogenation reaction pathways and possible mechanisms of the combined system are, however, still under investigation.

In an effort to develop reversible metal borohydrides with high hydrogen storage capacities and low dehydriding temperature, doping LiBH4 with various metal halides and hydrides has been conducted. Several metal halides such as TiCl3, TiF3, and ZnF2 effectively reduced the dehydriding temperature through a cation exchange interaction. Some of the halide doped LiBH4 are partially reversible. The LiBH4 + 0.1TiF3 desorbed 3.5 wt % and 8.5 wt % hydrogen at 150 and 450 °C, respectively, with subsequent reabsorption of 6 wt % hydrogen at 500 °C and 70 bar observed. XRD and NMR analysis of the rehydrided samples confirmed the reformation of LiBH4. The existence of the (B12H12)−2 species in dehydrided and rehydrided samples gives insight into the resultant partial reversibility. A number of other halides, MgF2, MgCl2, CaCl2, SrCl2, and FeCl3, did not reduce the dehydriding temperature of LiBH4 significantly. XRD and TGA-RGA analyses indicated that an increasing proportion of halides such as TiCl3, TiF3, and ZnCl2 from 0.1 to 0.5 mol makes lithium borohydrides less stable and volatile. Although the less stable borohydrides such as LiBH4 + 0.5TiCl3, LiBH4 + 0.5TiF3, and LiBH4 + 0.5ZnCl2 release hydrogen at room temperature, they are not reversible due to unrecoverable boron loss caused by diborane emission. In most cases, doping that produced less stable borohydrides also reduced the reversible hydrogen uptake. It was also observed that halide doping changed the melting points and reduced air sensitivity of lithium borohydrides.

Small-angle neutron scattering (SANS), nuclear magnetic resonance (NMR), wide-angle and small-angle X-ray scattering (WAXS and SAXS) measurements were carried out to investigate the three morphological forms of polyaniline emeraldine base (PANI-EB): unstructured, microtubes, and nanofibers. Although the chemical backbone between these two materials is quite similar, their solid structures are quite different, showing differences in the molecular conformation and supramolecular packing. Detailed solid-state 13C and 15N NMR characterization of PANI nanofibers (compared to the unstructured, granular form) revealed a slight variation in the structural features of the polymer that led to some differences in the chemical environments of the respective nuclei. The presence of two extra-sharp peaks at 96.5 and 179.8 ppm is a distinct feature found exclusively in the nanofiber spectra. Moreover, the crosspolarization (CP) dynamics study disclosed the presence of a complete set of sharp NMR peaks that are responsible for the presence of a more ordered morphology in the nanofiber. Small-angle neutron scattering indicated very sharp interfaces in the PANI fibers, which are well organized and have extremely sharp domains within the length scales probed (not, vert, similar10–1 nm). Overall, the X-ray scattering and spectroscopy data suggest that the nanofiber form is structurally different from the unstructured, PANI-EB powder. These differences are manifested, in part, by the additional chemistry occurring during the synthesis of the nanofibers.

A new molecular sieve topology has been determined from a multistage Monte Carlo computer simulation procedure using the program ZEFSAII. The material, SSZ-77, consists of alternating layers present in the RUT and AST topologies, and intergrowths may be possible in the way that this material grows. The product first arose from a synthesis where it appears that the degradation of the quaternary ammonium structure directing agent (SDA) produced the viable organo-guest molecule in the structure formation. The synthesis requires the use of Ge as well as Si as lattice components. In the absence of Ge, only RUT forms. An additional study was carried out to determine the suitable size of guest molecules in a series spanning trimethylamine to tetraethylammonium in the presence of benzyltrimethylammonium. It is found from NMR investigations that none of the larger molecules are occluded within the cages of the SSZ-77 structure, and that the primary occluded species is trimethylamine or tetramethylammonium.

^(11)B NMR spectroscopy has been employed to identify the reaction intermediates and products formed in the amorphous phase during the thermal hydrogen desorption of metal tetrahydroborates (borohydrides) LiBH_4, Mg(BH_4)_2, LiSc(BH_4)_4, and the mixed Ca(AlH_4)_(2-)LiBH_4 system. The ^(11)B magic angle spinning (MAS) and cross polarization magic angle spinning (CPMAS) spectral features of the amorphous intermediate species closely coincide with those of a model compound, closo-borane K2B_(12)H_(12) that contains the [B_(12)H_(12)]^(2-) anion. The presence of [B_(12)H_(12)]^(2-) in the partially decomposed borohydrides was further confirmed by high-resolution solution ^(11)B and ^1H NMR spectra after dissolution of the intermediate desorption powders in water. The formation of the closo-borane structure is observed as a major intermediate species in all of the metal borohydride systems we have examined.

Multinuclear and multidimensional solid state NMR techniques including magic-angle-spinning (MAS) and multiple-quantum (MQ) MAS experiments have been used to characterize various AlH_3 samples. At least three distinct polymorphic AlH_3 phases have been prepared by desolvating the alane etherate product from its organometallic synthesis. MAS-NMR spectra for the ^(1)H and ^(27)Al nuclei have been obtained on a variety of AlH_3 samples that include the β- and γ-phases as well as the α-phase. ^(27)Al MAS NMR was found to respond with high sensitivity for showing differences in spatial arrangements of AlH_6 octahedra in the three polymorphs studied. Based on the characteristic NMR signatures determined, phase transition of the γ-AlH_3 to the α-AlH_3 was studied at room and high temperatures. Direct decomposition of the γ-AlH_3 to aluminum metal at room temperature was also unambiguously confirmed by NMR studies.

The crystalline structure of a 7 Li and 11 B labeled lithium borohydride has been investigated using neutron powder diffraction at 3.5, 360, and 400 K. The B–H bond lengths and H–B–H angles for the [BH4] � tetrahedra indicated that the tetrahedra maintained a nearly ideal configuration throughout the temperature range investigated. The atomic displacement parameters at 360 K suggest that the [BH4] � tetrahedra become increasingly disordered as a result of large amplitude librational and reorientational motions as the orthorhombic to hexagonal phase transition (T ¼ 384 K) is approached. In the high-temperature hexagonal phase, the [BH4] � tetrahedra displayed extreme disorder about the trigonal axis along which they are aligned. Neutron vibrational spectroscopy data were collected at 5 K over an energy range of 10–170 meV, and were found to be in good agreement with prior Raman and low-resolution neutron spectroscopy studies.

We discuss the use of nuclear magnetic resonance (NMR) spectroscopy to investigate the physical state of the eutectic composition of LiBH_(4)–Ca(BH_4)_2 (LC) infiltrated into mesoporous scaffolds and the interface effect of various scaffolds. Eutectic melting and the melt infiltration of mixed borohydrides were observed through in situ NMR. In situ and ex situ NMR results for LC mixed with mesoporous scaffolds indicate that LiBH_4 and Ca(BH_4)_2 exist as an amorphous mixture inside of the pores after infiltration. Surprisingly, the confinement of the eutectic LC mixture within the mesopores is initiated below the melting temperature, which indicates a certain interaction between the borohydrides and the mesoporous scaffolds. The confined borohydrides remain inside of the pores after cooling. These phenomena were not observed in microporous or nonporous materials, and this observation highlights the importance of the pore structure of the scaffolds. Such surface interactions may be associated with a faster dehydrogenation of the nanoconfined borohydrides.

A highly electrophilic cationic PdII complex, [Pd(MeCN)_4][BF_4]_2 (1), brings about the preferential activation of the B–H bond in ammonia-borane (NH3·BH3, AB). At room temperature, the reaction between 1 in CH_3NO_2 and AB in tetraglyme leads to Pd nanoparticles and formation of spent fuels of the general formula MeNH_xBO_y as reaction byproducts, while 2 equiv. of H_2 is efficiently released per AB equiv. at room temperature within 60 seconds. For a mechanistic understanding of dehydrogenation by 1, the chemical structures of spent fuels were intensely characterized by a series of analyses such as elemental analysis (EA), X-ray photoelectron spectroscopy (XPS), solid state magic-angle-spinning (MAS) NMR spectra (^2H, ^(13)C, ^(15)N, and ^(11)B), and cross polarization (CP) MAS methods. During AB dehydrogenation, the involvement of MeNO2 in the spent fuels showed that the mechanism of dehydrogenation catalyzed by 1 is different from that found in the previously reported results. This AB dehydrogenation derived from MeNO_2 is supported by a subsequent digestion experiment of the AB spent fuel: B(OMe)_3 and N-methylhydroxylamine ([Me(OH)N]_2CH_2), which are formed by the methanolysis of the AB spent fuel (MeNH_xBO_y), were identified by means of ^(11)B NMR and single crystal structural analysis, respectively. A similar catalytic behavior was also observed in the AB dehydrogenation catalyzed by a nickel catalyst, [Ni(MeCN)_6][BF_4]_2 (2).

The germanosilicate ITQ-24 (IWR framework type) was synthesized in fluoride medium using 1,3,5-tris(1,2-dimethylimidazolium) benzene as the structure directing agent (SDA). A structure analysis of the as-synthesized ITQ-24 material using synchrotron powder diffraction data and difference electron density calculations have allowed the fluoride ions and the germanium atoms to be located and the conformation of the SDA to be determined. The benzyl ring is perpendicular to the b axis with the three imidazolium moieties forming a “T-shaped” arrangement. Ge atoms replace some of the Si in the double-4-ring (d4r) and in one of the single-4-rings (s4r). The other s4r contains only Si. Fluoride ions are in the d4r units. Initially, the space group Cmmm (highest possible symmetry) was assumed, but the framework geometry was strained. An independent evaluation of the symmetry using the powder charge flipping algorithm in Superflip led to a successful refinement with reasonable geometry and a refined composition of |[(C_6H_3)(C_7H_(10)N_2)_3]_2F_2|[Si_(40.2)Ge_(15.8)O_(112)] in the space group Pban.

This study surveys the use of a range of structure-directing agents (SDA) in zeolite synthesis experiments under the conditions using HF. The studies made are all for systems containing only silica as the inorganic component. Key points to emerge from the study are a reinforcement of the concept of more open-framework host structures forming when the reactions are more concentrated (lower H2O/SiO2 ratios). This discovery had been reported previously from the research group at ITQ in Valencia, Spain. Our studies show that some novel all-silica compositions have been achieved using this route for synthesis. Two new relationships we explore are whether the use of fluoride anion in synthesis has different nucleation selectivities as a function of dilution, and whether guest molecules can achieve tighter packing in the host structures using the fluoride route as contrasted with the hydroxide route. We explore this with MAS NMR studies. We find that some large organo-cations, which produce no products in alkaline media, give interesting host structure in the fluoride reactions. To cite this article: S.I. Zones et al., C. R. Chimie 8 (2005).

This work is an experimental response to an intriguing paper recently published by Catlow and co-workers, which looked at the computational feasibility of fluorine location in three different all-silica zeotypes (Attfield, M. P.; Catlow, C. R. A.; Sokol, A. A. Chem. Mater. 2001, 13, 4708). The materials were chosen as representative of three unique host locations. Our present work examined the synthesis of zeotypes AST, IFR, and MTT using organo-cations with a strong preference for crystallizing these structures. We studied the effect of reaction time and the H(2)O/SiO(2) reactant ratio. The latter is probably the most important function in these zeolite crystallizations that use HF. As reaction conditions became more dilute, AST gave way to SGT and IFR to MTW as host structures, while the MTT synthesis was invariant. Our reactions were studied in terms of product yield vs time, product organo-cation content, fluorine content, and the representative (29)Si and (19)F NMR spectra for certain samples. A single crystal study was carried out for a sample of MTT. Our results showed that, consistent with other recent studies, low H(2)O/SiO(2) reactant ratios lead to more open framework host structures (i.e., IFR vs MTW), and there is typically a higher uptake of organo-cation and fluorine. The structure may well contain a higher population of 4-rings within the silicate substructure. While MTT that contains no 4-rings was chosen as the best possible candidate to achieve an ion-pair for the organo-cation and fluoride anion within the silicate host, both NMR and single crystal work confirm that fluoride is bonded to a 5-coordinate silica center within the lattice.

Neutral Ni(II) salicylaldimine catalysts (pendant ligand NCMe or PPh3) were used to copolymerize ethylene with monomers containing esters, alcohols, anhydrides, and amides and yielded linear functionalized polyethylene in a single step. -Olefins and polycyclic olefin comonomers carrying functionality were directly incorporated into the polyethylene backbone by the catalysts without any cocatalyst, catalyst initiator, or other disturber compounds. The degree of comonomer incorporation was related to the monomer structure: tricyclononenes norbornenes -olefins. A wide range of comonomer incorporation, up to 30 mol %, was achieved while a linear polyethylene structure was maintained under mild conditions (40 °C, 100 psi ethylene). Results from the characterization of the copolymers by solution and solid-state NMR techniques, thermal analysis, and molecular weight demonstrated that the materials contained a relatively pure microstructure for a functionalized polyethylene that was prepared in one step with no catalyst additive. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2842–2854, 2002

A novel one-pot process that can produce freestanding reduced graphene oxide (RGO) sheets in large scale through a mechanochemical method is presented, which is based on a 1:1 adduct of hydrazine and carbon dioxide (H_3N^+NHCO_2^−, solid hydrazine). We were able to synthesize RGO sheets by grinding solid hydrazine with graphene oxide (GO), followed by storing the mixed powder at 50 °C for 10 min. No solvents, nor large vessels, nor post-annealing at high temperatures are required. The resulting RGO sample was characterized by elemental analysis, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, Brunauer–Emmett–Teller measurement, thermo gravimetric analysis, Fourier transform infrared spectroscopy, solid state nuclear magnetic resonance spectroscopy, and conductivity measurement. It exhibits excellent conductivity and possesses a high specific surface area. This reduction method was successfully applied for the fabrication of inkjet-printed RGO devices on a flexible substrate.

Layered borosilicate zeolite precursor ERB-1P (Si/B = 11) is delaminated via simultaneous deboronation and SDA removal, to yield material DZ-1 consisting of silanol nests, using a simple aqueous Zn(NO_3)_2 treatment. Characterization of this synthesis process by PXRD shows loss of long-range order, and transmission electron microscopy (TEM) demonstrates transformation of rectilinear layers in the layered zeolite precursor to single and curved layers in the delaminated material. N_2 physisorption confirms the expected decrease of micropore volume and increase in external surface area for delaminated materials relative to their calcined 3D zeolite counterpart. Elemental analysis shows loss of B and absence of Zn in the delaminated material. Resonances corresponding to silanol nests are evident via^(29)Si solid-state NMR spectroscopy in DZ-1, which should be located within 12-MR pockets near the external surface. We have successfully utilized these nests as tetrahedral recognition sites for incorporation of Ti within an isolated framework coordination environment in material Ti-DZ-1. Diffuse-reflectance ultraviolet (DR-UV) spectroscopy of Ti-DZ-1 confirms isolated framework Ti sites, which are assigned to bands in the range of 210 nm–230 nm. Infrared spectra of Ti-DZ-1 consist of a distinct absorption band at 960 cm^(−1), which is absent in DZ-1 prior to Ti incorporation and has been previously correlated with the presence of framework Ti species. Infrared spectra after pyridine adsorption demonstrate bands consistent with Lewis-acid sites in the resulting Ti-substituted delaminated zeolite. The accessibility of these Lewis-acid sites is confirmed when using Ti-DZ-1 as a catalyst for cyclohexene epoxidation using tert-butyl hydroperoxide as the organic oxidant – a reaction for which both DZ-1 and TS-1 are inactive.

A zeolite synthesis system is described in which a minor amount of structure-directing agent is used to specify the nucleation product, and then a larger amount of an amine is used to provide both pore filling and basicity capacities in the synthesis. A number of syntheses of different zeolite products are described for reactions in the SiO2/Al2O3 range of 35, which are conditions which yield high silica zeolites but are toward the more catalytically active end of the SiO2/Al2O3 spectrum. There are a number of cost-saving benefits described for this synthesis route including reduced structure-directing agent cost, waste stream cleanup costs, and time in reactor and reagent flexibility. Some details of the reaction are shown for this route to zeolite SSZ-25. The reaction was also used as a way to screen a new structure-directing agent, and zeolite SSZ-47 was discovered in this manner. The surprisingly high inorganic cation uptake in some of the zeolite products also may indicate that they play an important...

The synthesis of aluminosilicate zeolite, SSZ-25, is described using a two-component organic guest molecule strategy. This method has been recently described by us and is quite effective in crystallizing a variety of aluminosilicate zeolites with reduction in template cost. In this instance the original organic guest component used in the discovery of SSZ-25, N',N',N'-trimethyl-2-adamantammonium cation, is used in conjunction with a variety of smaller amines. The amine is the major organic component in the synthesis and the quaternary ammonium compound, while a minor component, is essential for structure direction to the desired zeolite product. Studies here show that the adamantyl component is preferentially taken up during crystal growth. Our studies showed that the use of the multi-organic component approach to synthesis resulted in a faster and cheaper route to crystallizing SSZ-25. The SSZ-25 has been described in the literature as having the MWW topology and as such has two different channel systems accessed by 10-ring openings; the channel systems do not intersect. One set of 10-rings open into large cavities. In this study we used NMR spectroscopy to examine the as-made materials and to see if the two organic components are used in different capacities in the synthesis, probing if the admantyl component is only found in these larger cavities. The crystalline products could be affected by solvent extraction with polar solvents like dimethylformamide: the X-ray powder patterns and elemental analyses changed with solvent treatment. The solvent-treated crystals were studied by NMR spectroscopy, elemental analysis, and argon adsorption. The two-component organic guest approach was also found to be quite flexible not only with regard to the amine, but also towards the quaternary ammonium compounds. Non-adamantyl polycyclic templates could be used, and polar but non-quaternized adamantyl derivatives also succeeded in directing towards SSZ-25 formation. On the other hand. in one instance it was shown that the two-component approach favors SSZ-25 as the kinetic product but at longer run times Ostwald ripening was observed, leading to the disappearance of SSZ-25 and formation of ferrierite zeolite and quartz.

A new method for synthesizing ∗BEA-type molecular sieves that involves the use of mesoporous materials as reagents is presented. Si-Beta (pure-silica, ∗BEA-type molecular sieve) is synthesized by heating TEAOH-impregnated Si-MCM-41 to 150°C for several days. The Si-Beta obtained has a small number of Q3 sites that are mostly siloxy groups that balance the charge of TEA cations. TEA cations can easily be removed by contacting the Si-Beta with acetic acid solution, and as a result, a highly hydrophobic Si-Beta is formed. Ti-Beta is synthesized from Ti-containing mesoporous silica or Ti-impregnated Si-MCM-41 without adding Al3+, alkali-metal cations and seeds. The incorporation of Ti into the ∗BEA structure is confirmed by UV–vis data. ∗BEA-type materials that contain other species such as Al, B, V, Zr and Zn can also be prepared.

In situ solid-state NMR methodologies have been employed to investigate the photocatalytic oxidation of ethanol (C2H5OH) over a TiO2-coated optical microfiber catalyst and two other TiO2-based catalysts. Adsorption of ethanol on the surface of the TiO2/optical microfiber catalyst formed a strongly hydrogen-bonded species and a Ti ethoxide species. In situ UV irradiation experiments under 13C magic angle spinning (MAS) conditions reveal the formation of two main reaction intermediates, 1,1-diethoxyethane (CH3CH(OC2H5)2) and acetic acid, under dry conditions. The catalyst was shown to be highly effective for the degradation of ethanol as complete photooxidation of ethanol was observed to form acetic acid and CO2. These results were compared to those using a monolayer catalyst supported on porous Vycor glass and powdered TiO2. Solid-state NMR investigations on TiO2 powder modeled after temperature-programmed desorption experiments confirm the identities of the hydrogen-bonded and Ti ethoxide species and show...

In situ solid-state NMR methodologies have been employed to investigate the photocatalytic oxidation of ethanol (C2H5OH) over two TiO2-based catalysts, Degussa P-25 powder and a monolayer TiO2 catalyst dispersed on porous Vycor glass. Two adsorption sites were observed for ethanol, a chemisorbed species identified as an ethoxide species, and a hydrogen-bonded species. The Ti-bound ethoxide was found to be the more photocatalytically reactive species. 13 C magic-angle spinning (MAS) experiments revealed that long-lived intermediates, including acetaldehyde (CH3CHO), acetic acid, formic acid, and acetate were observed under dry conditions and in the presence of molecular oxygen. Similar reaction intermediates form on the surfaces of both catalysts. 13 C cross-polarization MAS experiments allowed us to identify and follow the evolution of surface-bound species during UV irradiation. Acetate, which forms from mobile acetic acid, appears to be bound to the non-irradiated surfaces of the powdered TiO2 catalyst, and was also observed on the surface of TiO2/PVG catalyst, and further degradation was not possible. The presence of molecular oxygen was found to be essential for photooxidation to proceed.

In situ solid-state NMR methodologies have been employed to investigate the photocatalytic oxidation of trichloroethylene (TCE) over two TiO2-based catalysts, Degussa P-25 powder and a monolayer Ti...

Beyond hydrogen storage: The first example of reversible magnesium deposition/stripping onto/from an inorganic salt was seen for a magnesium borohydride electrolyte. High coulombic efficiency of up to 94 % was achieved in dimethoxyethane solvent. This Mg(BH(4))(2) electrolyte was utilized in a rechargeable magnesium battery.

Herein, we present a lithium-doped fullerane (Li(x)-C(60)-H(y)) that is capable of reversibly storing hydrogen through chemisorption at elevated temperatures and pressures. This system is unique in that hydrogen is closely associated with lithium and carbon upon rehydrogenation of the material and that the weight percent of H(2) stored in the material is intimately linked to the stoichiometric ratio of Li:C(60) in the material. Characterization of the material (IR, Raman, UV-vis, XRD, LDI-TOF-MS, and NMR) indicates that a lithium-doped fullerane is formed upon rehydrogenation in which the active hydrogen storage material is similar to a hydrogenated fullerene. Under optimized conditions, a lithium-doped fullerane with a Li:C(60) mole ratio of 6:1 can reversibly desorb up to 5 wt % H(2) with an onset temperature of ~270 °C, which is significantly less than the desorption temperature of hydrogenated fullerenes (C(60)H(x)) and pure lithium hydride (decomposition temperature 500-600 and 670 °C respectively). However, our Li(x)-C(60)-H(y) system does not suffer from the same drawbacks as typical hydrogenated fullerenes (high desorption T and release of hydrocarbons) because the fullerene cage remains mostly intact and is only slightly modified during multiple hydrogen desorption/absorption cycles. We also observed a reversible phase transition of C(60) in the material from face-centered cubic to body-centered cubic at high levels of hydrogenation.

New material UCB-1 is synthesized via the delamination of zeolite precursor MCM-22 (P) at pH 9 using an aqueous solution of cetyltrimethylammonium bromide, tetrabutylammonium fluoride, and tetrabutylammonium chloride at 353 K. Characterization by powder X-ray diffraction, transmission electron microscopy, and nitrogen physisorption at 77 K indicates the same degree of delamination in UCB-1 as previously reported for delaminated zeolite precursors, which require a pH of greater than 13.5 and sonication in order to achieve exfoliation. UCB-1 consists of a high degree of structural integrity via ^(29)Si MAS NMR and Fourier transform infrared spectroscopies, and no detectable formation of amorphous silica phase via transmission electron microscopy. Porosimetry measurements demonstrate a lack of hysteresis in the N_2 adsorption/desorption isotherms and macroporosity in UCB-1. The new method is generalizable to a variety of Si:Al ratios and leads to delaminated zeolite precursor materials lacking amorphization.

The conventional method of data analysis and interpretation of time‐resolved multiple quantum (MQ) nuclear magnetic resonance (NMR) spectra of solids is closely examined. Intensity profiles of experimental 1H MQ NMR spectra of polycrystalline adamantane and hexamethylbenzene serve to test the Gaussian statistical model approach. Consequences of this model are explored with a least‐squares fitting procedure, transformation of data to yield linear plots, and a scaling analysis. Non‐Gaussian behavior of the MQ NMR spectral intensity profiles, as a function of order of coherences, is demonstrated with all these methods of analysis. A heuristic argument, based on the multiplicative properties of dipolar coupling constants in the equation of motion of the density operator, leads to the prediction of exponentially decaying MQ NMR spectral intensity profiles. Scaling analysis and semilog plots of experimental time‐resolved MQ NMR spectra of adamantane and hexamethylbenzene support this deduction. Dynamical scale ...

The concepts involved in production and detection of n-quantum coherence in nuclear magnetic resonance (NMR) are considered. The use of coherent averaging to reduce internal Hamiltonians to zero, and to something other than their non-averaged values is reviewed. The experimental procedure necessary to produce and detect multiple quantum coherence in strongly dipolar coupled spin 1 2 solids is described. This procedure, using a single quantum propagator described in the initial sections, is then used to probe the densities (as distinguished from the chemical identities supplied by a 1-quantum fingerprint) of protons on silica gel surfaces of fumed, Cab-O-Sil HS5 silica gels which have: (a) not been relaxed by hydration, but have been reduced under flowing hydrogen; (b) been relaxed by hydration and subsequently reduced; (c) had deposited particles of metallic Ru, Pt, and Ag. As reflected in the highest order of multiple quantum coherence observed under a fixed time for development, the relaxed and reduced sample, and the sample with Ru deposited on it exhibit lower densities of protons than do the other samples. The implications to assuming that silica gel is an “inert” support for reactions involving reactions of hydrocarbons on supported metal catalysts are discussed.

[Pd(allyl)]BF4 (I), [Pd(allyl)(2,4-hexadiene)]BF4 (II), and [Pd(MeCN)4](BF4)2 (III) catalyze the dehydrogenation of NH3BH3 most efficiently with a release of 2.0 equiv.