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Conjugated microporous polymers (CMPs) are a prospective class of porous materials that are promising in a wide variety of applications due to their outstanding physical and chemical properties.

Herein we report the rational syntheses of three conjugated microporous polymers (CMPs) through one-pot polycondensation couplings of a boronated triphenylpyridine (TPP-3Bor) with 4,7-bis(5-bromothien-2-yl)benzo[c][1,2,5]thiadiazole (ThZ-2Br), 2,5-dibromothiophene (Th-2Br), and 1,4-dibromobenzene (Bz-2Br), yielding...

Formic acid (HCOOH) is an important intermediate in chemical synthesis, pharmaceuticals, the food industry, and leather tanning and is considered to be an effective hydrogen storage molecule. Direct contact with its vapor and its inhalation lead to burns, nerve injury, and dermatosis. Thus, it is critical to establish efficient sensing materials and devices for the rapid detection of HCOOH. In the present study, we introduce a chemical sensor based on a quartz crystal microbalance (QCM) sensor capable of detecting trace amounts of HCOOH. This sensor is composed of colloidal phenyl-terminated carbon nitride (Ph-g-C3N4) quantum nanoflakes prepared using a facile solid-state method involving the supramolecular preorganization technology. In contrast to other synthetic methods of modified carbon nitride materials, this approach requires no hard templates, hazardous chemicals, or hydrothermal treatments. Comprehensive characterization and density functional theory (DFT) calculations revealed that the QCM sensor designed and prepared here exhibits enhanced detection sensitivity and selectivity for volatile HCOOH, which originates from chemical and hydrogen-bonding interactions between HCOOH and the surface of Ph-g-C3N4. According to DFT results, HCOOH is located close to the cavity of the Ph-g-C3N4 unit, with bonding to graphitic carbon and pyridinic nitrogen atoms of the nanoflake. The sensitivity of the Ph-g-C3N4-nanoflake-based QCM sensor was found to be the highest (128.99 Hz ppm-1) of the substances studied, with a limit of detection (LOD) of HCOOH down to a sub-ppm level of 80 ppb. This sensing technology based on phenyl-terminated attached-g-C3N4 nanoflakes establishes a simple, low-cost solution to improve the performance of QCM sensors for the effective discrimination of HCOOH, HCHO, and CH3COOH vapors using smart electronic noses.

Unit-cell-thin zeolitic nanosheets have emerged as fascinating materials for catalysis and separation. The controllability of nanosheets stacking is extremely challenging in the chemistry of two-dimensional zeolitic materials. So far, the organization of zeolitic nanosheets in hydrothermal synthesis has been limited by the lack of tunable control over the guest-host interactions between organic structure-directing agents (OSDAs) and zeolitic nanosheets. Here, we report a direct synthetic methodology that enables systematic manipulation of the aluminosilicate MWW-type nanosheets stacking. Variable control of guest-host interactions is rationally achieved by synergistically altering the charge density of OSDAs and synthetic silica-to-alumina composition. These finely-controlled interactions allow the successful preparation of series of three-dimensional (3D) zeolites with MWW-layer stacking in wide ranges from variations of disorder to fully-order, leading to tunable catalytic activity in cracking reaction. These results highlight unprecedented opportunities to modulate zeolitic nanosheets arrangement in 3D zeolites whose structure can be tailored for catalysis and separation.

The synthesis time for CON-type aluminoborosilicate zeolite ([Al, B]-CON), a promising catalyst for methanol-to-olefin reactions, was reduced from 20 h to 45 min, the fastest reported so far for this zeolite. In addition to overcoming thermal lag by the use of tubular reactors at high temperatures, optimizing the reactant composition, choosing proper seed crystals, their quantity, size, and timing of addition were also instrumental in the fast-paced synthesis of [Al, B]-CON. It was found that obtaining a pure CON phase at a faster rate depends not only on the synthesis temperature, but also on the ageing temperature, amount of seed, and their partial dissolution. The fast synthesis of [Al, B]-CON could be an option for mass production using a demonstrated continuous flow synthesis system. The catalytic activity and stability of the fast-synthesized [Al, B]-CON was improved by the introduction of mesopores via alkaline treatment with amphiphilic molecules.

Organic structure-directing agents (OSDAs) are often employed for synthesis of zeolites with desired frameworks. A priori prediction of such OSDAs has mainly relied on the interaction energies between OSDAs and zeolite frameworks, without cost considerations. For practical purposes, the cost of OSDAs becomes a critical issue. Therefore, the development of a computational de novo prediction methodology that can speed up the trial-and-error cycle in the search for less expensive OSDAs is desired. This study utilized a nature-inspired ant colony optimization method to predict physicochemically and/or economically preferable OSDAs, while also taking molecular similarity and heuristics of zeolite synthesis into consideration. The prediction results included experimentally known OSDAs, candidates having structures closely related to known OSDAs, and novel ones, suggesting the applicability of this approach., Inspired by the exploratory methods of ant colonies, adaptive optimization was employed to explore the chemical space for organic molecules that guide zeolite crystallization, giving both physicochemically and economically promising molecules.

There is growing interest in developing mesoporous metallic alloys for electrochemical applications such as catalysts in fuel cells and batteries. As is well known, the chemical compositions of alloys can significantly affect their electrochemical properties. Although tuning the chemical compositions of mesoporous metallic alloys for enhancing the electrochemical activity has been reported, they have mostly been limited to binary components partly because experimental exploration over possible multi-compositional spaces is a time-consuming process. Here, we describe, for the first time, the application of the active learning scheme using Bayesian optimization for the exploratory search of the chemical compositions of mesoporous trimetallic PtPdAu alloys with optimum catalytic activity in the electrocatalytic oxidation of methanol. Unexpectedly, it was found that the PtPdAu alloys yielding the highest catalytic activity contain only a small percentage of Au. These compositions were discovered by performing only 47 experiments, less than 1% of all possible compositions in our experimental design. Our current approach is highly efficient and would be applicable to any system to accelerate the discovery of novel materials.

A data-intensive approach scours known organics for synthesizing targeted zeolites

Materials science and chemistry have played a central and significant role in advancing our society. With the shift toward sustainable living, it is anticipated that the development of functional materials will continue to be vital for sustaining life on our planet. In the recent decades, rapid progress has been made in materials science and chemistry owing to the advances in experimental, analytical, and computational methods, thereby producing several novel and useful materials. However, most problems in material development are highly complex. In this review article, we discuss the best strategy for the development of functional materials via the implementation of three key concepts: nanotechnology as a game changer, nanoarchitectonics as an integrator, and materials informatics as a super accelerator. Discussions from conceptual viewpoints and exemplified recent developments, chiefly focused on nanoporous materials, are presented. We anticipate that coupling these three strategies together will open advanced routes for the swift designing and exploratory search of functional materials truly useful for solving real-world problems. These novel strategies will result in the evolution of nanoporous functional materials. This article is protected by copyright. All rights reserved.

There is broad scientific interest in lamellar zeolitic materials for a large variety of technological applications. The traditional synthetic methods towards two-dimensional (2D) zeolitic precursors have made a great impact in the construction of families of related zeolites; however, the connection between structurally distinct 2D zeolitic precursors is much less investigated in comparison, thereby resulting in a synthetic obstacle that theoretically limits the types of zeolites that can be constructed from each layer. Herein, we report a Ge-recycling strategy for the topotactic conversion between different 2D zeolitic precursors through a three-dimensional (3D) germanosilicate. Specifically, the intermediate germanosilicate can be constructed within 150 min by taking advantage of its structural similarity with the parent lamellar precursor. This process enables the conversion of one 2D zeolite structure into another distinct structure, thus overcoming the synthetic obstacle between two families of zeolitic materials.

Designing efficient synthesis methodologies, without using expensive organic structure-directing agents (OSDAs), for industrially important zeolites is of high significance not only to realize thei...

Porous inorganic–organic hybrid polymers (PHPs) with cyclic siloxane frameworks are synthesized via Friedel–Crafts alkylation between siloxane molecules and formaldehyde dimethyl acetal. The synthesized polymers with high specific surface areas (up to 1310 m2 g−1) show a combination of type I(b) and type IV(a) isotherms, as determined by argon adsorption–desorption measurements, suggesting that they contain both micropores and mesopores. Interestingly, two different types of hysteresis loops are observed, depending solely on the organic substituting groups of the siloxane building blocks. PHPs synthesized from cyclic siloxane building blocks substituted with one methyl group and one phenyl group per one silicon atom show type H3 hysteresis loop; while those synthesized from cyclic siloxane building blocks substituted with two phenyl groups show type H2(a) hysteresis loop. This indicates that the resulting PHPs possess different porous networks. 29Si MAS NMR spectra indicate that the Si–phenyl covalent bonds are selectively cleaved during polymerization; while the Si–methyl bonds are not, leading to the formation of different pore structures.

Lewis acid Sn-BEA catalysts with tunable morphology and hydrophobicity were successfully synthesized by the recrystallization of post-synthetic Sn-BEA in the presence of ammonium fluoride (NH4F) and tetraethylammonium bromide (TEABr). Three-dimensionally ordered mesoporous imprinted (3DOm-i) and nanocrystalline Sn-BEA catalysts with hydrophobic surface were synthesized for the first time by the method. This recrystallization method includes the dissolution of crystalline zeolite BEA by fluoride ions and the rearrangement of different types of silanol defects in the presence of TEABr. The method allows the final products to simultaneously inherit the morphology of their parent Al-BEA zeolites, and significantly reduce silanol defects within the catalysts. The Sn-BEA catalysts synthesized from the recrystallization method show largely enhanced catalytic performance for both glucose isomerization and bulky lactose isomerization in different solvents, which is presumably due to the hydrophobic surface and improved molecular transport property in the hierarchical zeolites. The recrystallization approach is a facile and reliable strategy to improve the hydrophobicity of zeolite catalysts with tunable morphologies ranging from nanocrystals to hierarchical structures.

In order to realize designed synthesis, understanding the formation mechanism of zeolites at an atomic level has long been aspired, but remains challenging due to the fact that the knowledge of atomic configurations of the species formed during the process is limited. We focus on a synthesis system that crystallizes CHA zeolite from FAU zeolite as the sole source of tetrahedral atoms of Si and Al, so that end-to-end characterization can be conducted. Solid-state 29Si MAS NMR is followed by high-throughput computational modeling to understand how atomic configurations changed during the interzeolite conversion. This reveals that the structural motif commonly found in FAU and CHA is not preserved during the conversion; rather, there is a specific rearrangement of silicates and aluminates within the motif. The atomic configuration of CHA seems to be influenced by that of the starting FAU, considering that CHA synthesized without using FAU results in a random Al distribution. A Metropolis Monte-Carlo simulation combined with a lattice minimization technique reveals that CHA derived from FAU has energetically favorable, biased atomic locations, which could be a result of the atomic configurations of the starting FAU. These results suggest that by choosing the appropriate reactant, Al placement could be designed to enhance the targeted properties of zeolites for catalysis and adsorption.

Understanding the properties of zeolites for cation exchange is important because the ion-exchange performance largely determines their suitability in applications such as catalysis and adsorptive separation. We synthesized a Zn(ii)-incorporated mordenite-framework aluminosilicate zeolite (Zn,Al-MOR), in which both Zn and Al are substituted in the framework, and studied its ion-exchange behavior for multivalent cations. For comparison, the original aluminosilicate mordenite (Al-MOR) was also synthesized with a composition adjusted to ensure that its charge density was similar to that of Zn,Al-MOR. While the incorporation of Zn(ii) led to a slower kinetic process, the selectivities and the exchange capacities toward multivalent cations (especially divalent cations) were significantly improved. Herein, we discussed the mechanism responsible for improving the ion-exchange performance in the presence of Zn(ii) and found that the incorporation of Zn(ii) led to a significant improvement in the ion-exchange temperature dependence of the MOR, which led to the ability to enhance ion-exchange capacity through temperature control during actual application. It was also revealed that the presence of Zn(ii) significantly improves selectivity and spontaneity toward the exchange of multivalent cations, Ni2+. Moreover, XRD and nitrogen-adsorption/desorption analyses revealed that the structures of the materials are maintained during the ion exchange, which is indicative of superior structural stability and tolerance to ion exchange.

A facile method for synthesizing microporous zincosilicate *BEA molecular sieves was proposed using co-precipitated homogeneous zincosilicate gels containing the tetraethylammonium cation (TEA+) as an organic structure-directing agent. Characterization of the co-precipitated gels indicated that zinc species and TEA+ were distributed in the silicate matrix. Zincosilicate *BEA molecular sieves with a high zinc content were obtained from the gels, while highly crystalline molecular sieves could not be synthesized using conventional zinc and silicon sources under the same conditions.

International audience; The direct synthesis of hierarchically intergrown silicalite-1 can be achieved using a specific diquaternary ammonium agent. However, the location of these molecules in the zeolite framework, which is critical to understand the formation of the material, remains unclear. Where traditional characterization tools have previously failed, herein we use polarized stimulated Raman scattering (SRS) microscopy to resolve molecular organization inside few-micron-sized crystals. Through a combination of experiment and first-principles calculations, our investigation reveals the preferential location of the templating agent inside the linear pores of the MFI framework. Besides illustrating the attractiveness of SRS microscopy in the field of material science to study and spatially resolve local molecular distribution as well as orientation, these results can be exploited in the design of new templating agents for the preparation of hierarchical zeolites

The Al location in zeolites can have massive influences on the zeolite properties because it directly correlates with the cationic active sites. Herein, the synthesis of IFR zeolites with controlled Al distribution at different tetrahedral sites (T sites) is reported. The computational calculations suggest that organic structure-directing agents (OSDAs) used for zeolite synthesis can alter the energetically favorable T sites for Al. Zeolite products synthesized under identical conditions but with different OSDAs are found to have altered fractions of Al at different T sites in accordance with the energies derived from the zeolite-OSDA complexes. Our finding thus provides evidence for the ability of OSDAs to direct Al into more energetically favorable T sites, thereby offering rational synthetic guidelines for the selective placement of Al into specific crystallographic sites.

There is growing interest to develop zeolite materials capable of stabilizing divalent cations such as Cu2+ , Fe2+ , and Ni2+ for catalytic applications. Herein the synthesis of a new microporous zincosilicate with CHA zeolite topology is reported for the first time, by particularly focusing on the mixing procedures of the raw materials to prevent the precipitation of zinc oxides/hydroxides and the formation of impurity phases. The obtained zincosilicate CHA products possess remarkably higher ion-exchange ability for catalytically useful, divalent cations, demonstrated here using Ni2+ as an example, compared to that of aluminosilicate and zincoaluminosilicate analogs. It is anticipated that these zincosilicate CHA materials can be an efficient platform for several important catalytic reactions. In addition, the present finding would provide a general guideline for effective substitution of other heteroatoms into the zeolite frameworks.

We report the most siliceous FAU-type zeolite, HOU-3, prepared via a one-step organic-free synthesis route. Computational studies indicate that it is thermodynamically feasible to synthesize FAU with SAR=2-7, though kinetic factors seemingly impose a more restricted upper limit for HOU-3 (SAR≈3). Our findings suggest that a slow rate of crystallization and/or low concentration of Na+ ions in HOU-3 growth mixtures facilitate Si incorporation into the framework. Interestingly, Q4 (nAl) Si speciation measured by solid-state NMR can only be modeled with a few combinations of Al positioning at tetrahedral sites in the crystal unit cell, indicating the distribution of Si(-O-Si)4-n (-O-Al)n species is spatially biased as opposed to being random. Achieving higher SAR is desirable for improved zeolite (hydro)thermal stability and enhanced catalytic performance, which we demonstrate in benchmark tests that show HOU-3 is superior to commercial zeolite Y.

Meso- and/or macroporous zeolites have received particular attention because the presence of secondary meso- and/or macropores, in addition to the intrinsic micropores of zeolites, can provide addi...

Zeolites with hierarchical structures are of particular interest because such structures can improve molecular diffusion, particularly that of bulky molecules. N,N,N,N′,N′,N′-Hexapropylpentanediammonium cations (Pr6-diquat-5), a simple diquaternary ammonium organic structure-directing agent (OSDA), can direct the formation of hierarchically and sequentially intergrown MFI zeolites without employing any mesoporogens. In this paper, the effects of OSDAs having structures similar to Pr6-diquat-5 but different lengths of alkyl spacers and/or different substituting groups on the phase selectivity and morphology of the resulting zeolites are presented. It was revealed that the number of carbon atoms between two charged nitrogens in the OSDAs significantly affected the intergrowth and morphology of the crystals formed. In addition, the propyl-substituted OSDAs were found to be very selective to the formation of MFI zeolite, whereas the butyl-substituted OSDAs were not. For Pr6-diquat-5, the condition for the for...

Shortening the synthesis time of SSZ-16 (AFX type) zeolite from several days to 2 h has been achieved using an ultrafast synthesis route involving N,N,N′,N′-tetraethylbicyclo[2.2.2]oct-7-ene-2,3:5,6-dipyrrolidinium (TEBOP) as an organic structure-directing agent (OSDA) in a tubular reactor assisted by seed crystals. Recently, copper exchanged SSZ-16 has been looked upon as one of the few equivalents to SSZ-13 for the selective catalytic reduction of NOx with ammonia (NH3-SCR) from automobile exhausts. Hydrothermal stability is one of the crucial properties for any zeolites that compete for automobile applications. All the samples prepared were analyzed using sophisticated physio-chemical techniques and those prepared from TEBOP were subjected to SCR of NOx reactions. The rapid crystal growth induced by high synthesis temperature bestowed the ultrafast prepared SSZ-16 with high crystallinity and hydrothermal stability as well as enhanced SCR of NOx activity even when aged at 800 °C. Compared to 1,1′-(1,4-butanediyl)bis-4-aza-1-azoniabicyclo[2.2.2]octane dibromide (DABCO), TEBOP was found to be desirable as an OSDA for high crystallinity and hydrothermal stability.

Correlating synthesis conditions and their consequences is a significant challenge, particularly for materials formed as metastable phases via kinetically controlled pathways, such as zeolites, owing to a lack of descriptors that effectively illustrate the synthesis protocols and their corresponding results. This study analyzes the synthetic records of zeolites compiled from the literature using machine learning techniques to rationalize physicochemical, structural, and heuristic insights to their chemistry. The synthesis descriptors extracted from the machine learning models are used to identify structure descriptors with the appropriate importance. A similarity network of crystal structures based on the structure descriptors shows the formation of communities populated by synthetically similar materials, including those outside the dataset. Crossover experiments based on previously overlooked structural similarities reveal the synthesis similarity of zeolites, confirming the synthesis–structure relationship. This approach is applicable to any system to rationalize empirical knowledge, populate synthesis records, and discover novel materials., Understanding zeolite synthesis-structure relationships remains challenging owing to the number of variables involved in their preparation. Here the authors analyze zeolite synthetic records from the literature via machine learning and find communities of synthetically related materials with previously overlooked similarities.

Recent advances in strategies for synthesizing mesoporous silica particle (MSN) have enabled the precise control of its morphology, size, and composition which afford the applications in drug delivery and heterogeneous catalysis. Especially for drug delivery, the size of MSNs

Fine control over particle sizes and organic moieties of hollow organosilica nanoparticles is of importance towards practical applications of functional colloids in, for example, catalysis, drug delivery, and coating. Here, we report the versatile synthesis of hollow mesoporous organosilica nanoparticles with controllable particle sizes and diversified organic moieties using silica nanoparticles (SNs) as sacrificial, hard templates, which are removed by dissolution under alkali conditions. The resulting organosilica nanoparticles possessed size-tunable hollow interiors that can be accessed through mesoporous shells. The diameters of such hollow organosilica nanoparticles were easily controlled by altering the diameters of the SN templates, ranging from 12 to 170 nm. Organic moieties in the mesoporous shells can be diversified by changing the organosilica sources, (EtO)3Si–R–Si(OEt)3, where R = methylene, ethylene, and phenylene groups. In addition, it was revealed that there are minimum surface areas of the SN templates in the dispersions required to achieve the monodisperse silica/organosilica core/shell nanoparticles without homogeneous nucleation of organosilica nanoparticles. The nitrogen and argon adsorption–desorption isotherms of the resulting hollow organosilica nanoparticles showed type H5 hysteresis loops, which are derived from the mixed pore system of cage-like pores (hollow spaces) and open pores (interparticular voids between hollow organosilica nanoparticles). Hysteresis scanning measurements and NLDFT pore size distributions revealed the pore structures of the resulting hollow organosilica nanoparticles.

MFI zeolites exchanged with various cations have gained a great deal of attention as catalysts. Increase in the ion-exchange capacity of zeolites can improve their catalytic properties by introducing more active sites; however, the ion-exchange capacity of MFI zeolites is limited by maximum aluminum content in the structure. To improve the ion-exchange capability of the MFI zeolites beyond the upper limit of the aluminosilicate MFI zeolites, we propose herein an approach to incorporate Zn(ii) in the zeolitic framework, because Zn in the framework sites generates two negative charges per atom. Using zincoaluminosilicate gels prepared via co-precipitation, organic-free synthesis of zincoaluminosilicate MFI zeolites was achieved. The obtained zincoaluminosilicate MFI zeolites had high Zn contents comparable to those in the initial zincoaluminosilicate gels with both Zn and Al in the zeolite framework. In contrast, the use of conventional sources of Si, Al, and Zn resulted in zeolites with extra-framework zinc oxide species. The obtained Zn-substituted MFI zeolites were shown to possess higher ion-exchange capacity compared to aluminosilicate MFI zeolites. It was also revealed that the zincoaluminosilicate MFI zeolites have high affinity for the divalent cation compared to the aluminosilicate analog, likely due to the two negative charges in close proximity. Because of these higher ion-exchange efficiencies, especially for divalent cations, the obtained zincoaluminosilicate MFI zeolites are expected to be efficient platforms for several important catalytic reactions.

Synthesis of new zeolites involving organic molecules relies heavily on the trial-and-error approach, because it is difficult to interpret the determining effects of organics on zeolite crystal symmetry. Here, the intrinsic relationships among the space-filling of organics, included volume of channels, and zeolite crystal symmetry, are systematically demonstrated by experimental and computational means. Under controlled conditions, the "dimer" and "monomer" organics of 1-ethyl-3-methylimidazolium selectively direct different, but related, germanosilicates, the ECNU-16 with a new topology and the existing IM-16 with the UOS topology, respectively. The comprehensive computational study reveals that the zeolite phase selectivity is determined by the unique space-filling behavior of the "dimer" and "monomer" organics, which is closely correlated to their rotation freedom, as well as the included volume of host zeolite channels. The elucidation of this crucial space-filling effect from the fundamental viewpoint will provide new guidelines for the rational design and synthesis of new zeolites in future.

Hyperbranched amine polymers (HAS) grown from the mesoporous silica SBA-15 (hereafter "SBA-15-HAS") exhibit large capacities for CO2 adsorption. We have used static in situ and magic-angle spinning (MAS) ex situ (13)C nuclear magnetic resonance (NMR) to examine the adsorption of CO2 by SBA-15-HAS. (13)C NMR distinguishes the signal of gas-phase (13)CO2 from that of the chemisorbed species. HAS polymers possess primary, secondary, and tertiary amines, leading to multiple chemisorption reaction outcomes, including carbamate (RnNCOO(-)), carbamic acid (RnNCOOH), and bicarbonate (HCO3(-)) moieties. Carbamates and bicarbonate fall within a small (13)C chemical shift range (162-166 ppm), and a mixture was observed including carbamic acid and carbamate, the former disappearing upon evacuation of the sample. By examining the (13)C-(14)N dipolar coupling through low-field (B0 = 3 T) (13)C{(1)H} cross-polarization MAS NMR, carbamate is confirmed through splitting of the (13)C resonance. A third species that is either bicarbonate or a second carbamate is evident from bimodal T2 decay times of the ∼163 ppm peak, indicating the presence of two species comprising that single resonance. The mixture of products suggests that (1) the presence of amines and water leads to bicarbonate being present and/or (2) the multiple types of amine sites in HAS permit formation of chemically distinct carbamates.

NES-type aluminosilicate zeolites are successfully obtained for the first time without using organic structure-directing agents by the addition of zeolite EU-1, EUO-type aluminosilicate zeolites, as the seed crystals. Crystal growth of the NES-type zeolite using seed crystals with the different topology is presumed to be due to their structural similarities. The product phases in the seeded synthesis are strongly affected by the initial gel compositions such as SiO2/Al2O3 and Na2O/SiO2 ratios, and the pure NES-type zeolite is obtained only in a narrow region. Obtained product showed comparable pore characteristics to those of the NES-type zeolites synthesized using OSDAs.

Nanoporous silicas having some periodicity, high surface area (up to 1230 m(2) g(-1)), and pore diameters near the boundary between micro- and mesopores are synthesized using aromatic compounds bearing anionic end-groups as novel structure-directing agents (SDAs) that can facilitate multiple interactions between SDAs, co-SDAs and silica frameworks orthogonally.

Using near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, we shed light on the nature of the interaction between CO2 and the amine moieties in a hyperbranched aminosilica (HAS) material, a porous aminosilica composite with great potential for postcombustion carbon capture applications. We show that after dosing a pristine (annealed) HAS sample with CO2, the C K-edge NEXAFS spectrum presents a new π* resonance at 289.9 eV, which can be attributed to the formation of a C═O (carbonyl) bond. Additional analyses of the O K-edge using model samples containing carbamate, carbonate, and bicarbonate functional groups as reference demonstrate a carbamate bonding mechanism for the chemical adsorption of CO2 by the HAS material under the conditions employed. These findings show the capability of the C and O K-edge NEXAFS technique to identify CO2-adsorbate species despite the high concentration of C and O atoms inherently present in the sample (prior to CO2 dosing) and the significant similarities between the possible adsorbates.

Zeolites are crystalline microporous aluminosilicates that are constructed from corner-sharing, tetrahedrally coordinated TO4/2 primary units (where T is a tetrahedral atom – silicon or aluminum). Thanks to their unique crystalline framework structures, well-defined channels and cavities in a nanometer length scale, high surface areas, and several intrinsic properties arising from their anionic nature, zeolites have been widely used in various practical applications as adsorbents, ion exchangers, and catalysts. Zeolites have found their solid positions as key materials in industries and will continue to be the dominant industrial materials in future. Following a brief description of zeolite framework structures, in this chapter, the historical, fundamental, and recent aspects of zeolite synthesis are described. In addition, future prospects of zeolite toward the sustainable development are addressed. Keywords: catalytic conversions; hydrated alkali-metal cations; organic cations; porous solids; zeolite framework structures; zeolite synthesis; zeolite-like materials

Zeolites containing Zn in their frameworks are promising materials for ion-exchange and catalysis because of their unique ion-exchange capabilities and characteristic Lewis acidity. However, expensive organic compounds often required in their synthesis can prevent their practical uses. Here, a facile organic-free synthesis route for new zincoaluminosilicate zeolites having MOR topology, in which both Zn and Al are substituted in the framework, is demonstrated for the first time. The use of homogeneous zincoaluminosilicate gels prepared by a co-precipitation technique as raw materials is vital for the successful incorporation of both Zn and Al into the zeolite frameworks as revealed by several characterization techniques including solid-state NMR and UV-vis spectroscopy, and ion-exchange experiments. The obtained zincoaluminosilicate zeolites had high Zn contents comparable to those in the initial zincoaluminosilicate gels. In contrast, the uses of conventional sources of Si, Al, and Zn resulted in zeolites with very low contents of framework Zn or zeolites with extra-framework zinc oxide-species. FT-IR measurements using probe molecules and ion-exchange experiments suggested that there are two different environments of Zn in the zeolite frameworks. The obtained zincoaluminosilicate zeolites showed a higher ion-exchange efficiency for divalent cations such as nickel compared to the aluminosilicate analog. It is expected that the present co-precipitation technique is efficient for the incorporation of Zn (and other metals) into a variety of zeolite frameworks. To show its extended applicable scope, the synthesis of zincoaluminosilicate *BEA zeolite is also demonstrated.

The synthesis of aziridine-functionalized mesoporous silica membranes on polymeric hollow fibers is described, and their single-component CO2 and N2 permeation properties are investigated under both dry and humid conditions to elucidate the unusual permeation mechanisms observed in these membranes. Hollow fiber-supported mesoporous silica membranes are amine-functionalized with aziridine to yield hyperbranched aminopolymers within the membrane pores. The effects of the hyperbranched polymers in the mesopores on gas transport properties are investigated by single-component gas permeation measurements. The hyperbranched aminosilica membrane shows counterintuitive N2-selective (over CO2) permeation during operation under dry conditions. Further characterization of the permeation behavior reveals the effects of strong adsorption of CO2 under dry permeation conditions, leading to reduced CO2 diffusivity because of CO2-induced amine cross-linking in the mesopores. On the other hand, the hyperbranched aminosilic...

Seed-directed synthesis of zeolite without using organic structure-directing agents (OSDAs) has been considered to be a low-cost, environmentally friendly technique, potentially for application in the commercial manufacture of zeolites. The synthesis of zincosilicate zeolites by this method is thought to be more difficult than the aluminosilicate and borosilicate analogues, mainly because of the highly dissolution of zincosilicates in alkali solutions and the lack of comprehensive, structural information of intermediate zincosilicate species in zeolite synthesis systems. Here, a successful synthesis of zincosilicate zeolites possessing the VET-type structure by the seed-directed, OSDA-free method is reported for the first time. The obtained products show comparable pore characteristics and superior acidities to those of the seed crystals synthesized with OSDAs. In addition, VET-type zincoaluminosilicate zeolites are synthesized, which show better acidities than those of zincosilicate counterparts. In cont...

Lamellar azobenzene–siloxane hybrids were prepared by controlled hydrolysis and polycondensation of three types of precursors, where azobenzene is sandwiched by mono-, di- and triethoxysilyl groups using propylene linkers. All precursors underwent reversible and fast trans–cis isomerization upon UV/Vis irradiation in dilute solution. Upon hydrolysis of the triethoxysilylated precursor in a homogeneous solution under acidic conditions, precipitation occurred by self-assembly of hydrolyzed monomers into a lamellar structure. Although di- and mono-ethoxysilylated precursors produced less ordered products under identical conditions, highly ordered lamellar films were obtainable either by evaporation induced self-assembly of the hydrolyzed monomers or by solid-state reactions of precursor films. The degree of trans–cis isomerization of azobenzene moieties in the hybrid films was enhanced by decreasing the cross-linking degree of siloxane networks using precursors with less condensable alkoxy groups.

Porous materials have played an increasingly critical role in materials sciences and chemistry. From the viewpoint of applications, highly crystallized mesoporous architectures are very promising mainly due to their unique properties arising from the crystallized frameworks and many exciting applications in diverse fields. In this Highlight article, we summarize recent innovative researches in the creation of mesoporous architectures possessing crystalline pore walls. In particular, new strategies to synthesize highly crystallized mesoporous metals and metal oxides, metal–organic frameworks with large-sized mesopores, and zeolites with hierarchical mesoporosity are described. These mesoporous architectures show a lot of promise in energy and environment-related areas.

An alkanolamine, N,N,N′,N′-tetrakis(2-hydroxyethyl)ethylenediamine, is used as an organic structure-directing agent (OSDA) to synthesize aluminophosphate (AlPO-5) and silicoaluminophosphate (SAPO-5...

Amine/oxide hybrid carbon dioxide adsorbents prepared via impregnation of low molecular weight polymeric amines into porous oxide supports are among the most promising solid adsorbents developed for postcombustion CO2 capture or CO2 extraction from ambient air. The oxidative stability of adsorbents prepared by impregnation of poly(ethylenimine) (PEI) or poly(allylamine) (PAA) into mesoporous γ-alumina under humid oxidation conditions is evaluated in this work. The PEI-based adsorbents, which contain primary, secondary, and tertiary amines, are shown to degrade drastically at elevated temperatures (110 °C) and in high oxygen concentrations (21%, akin to air), with these effects reduced by both reductions in temperature (70 °C) and oxygen concentration (5%, akin to flue gas). The oxidation behavior of PEI-based adsorbents supported on alumina is qualitatively similar to past work on silica-supported PEI adsorbents. In contrast, the alumina-supported PAA adsorbents that contain only primary amines show signi...

Hierarchically organized porous materials can provide multidimensional spatial networks on different length scales with improved characteristics relevant to molecular diffusion. Zeolites that are microporous crystalline materials having pores and channels at molecular dimensions are of great importance for industrial applications. However, the presence of only micropores in zeolite frameworks often limits the molecular diffusion and therefore, restricts the transport of bulky molecules. This problem can be resolved by shortening the effective diffusion path lengths, which has been achieved by miniaturizing zeolite crystals, delaminating or exfoliating layered zeolites, synthesizing zeolite nanosheets, and introducing mesopores into zeolite particles. Among these solutions, the fabrication of hierarchical zeolites with microand mesoporosity is of interest because it combines intrinsic micropores with bypass-interconnected mesopores, and therefore, enhances both the micropore accessibility and molecular traffic within zeolite particles. Hierarchical zeolites have been produced using several techniques, including top-down desilication by alkali postsynthetic treatment and bottom-up directed assembly by hard or soft templates. The hard-template method requires multistep procedures and is therefore unfavorable for large-scale production. Alternatively, the direct introduction of organic mesopore-generating agents (mesoporogens) during zeolite synthesis can create uniform mesopores. The use of such mesoporogens is currently one of the most promising methods for the single-step construction of hierarchical zeolites. Progress has been made using well-designed mesoporogens composed of long hydrophobic chains and hydrophilic zeolitic structure-directing groups to generate zeolites with tunable mesoporosity and to direct the hierarchical assembly of zeolite nanosheets, yielding mesoporous zeolites with house-of-cards-like structures. These hierarchical nanosheets showed excellent catalytic performance in several important reactions because the presence of thin layers with specific crystalline faces facilitates catalysis at the exteriors or pore mouths. Such mesoporogens are probably necessary for the direct, singlestep synthesis of hierarchical zeolites. Herein we report an alternative, mesoporogen-free approach for the construction of hierarchically organized MFI zeolites by sequential intergrowth using a simple organic structure-directing agent (OSDA). The selection of an appropriate OSDA and optimized synthesis conditions that can form plate-like zeolites with enhanced 908 rotational intergrowths seems to be a key to achieving a hierarchical structure with three classes of porosity in one structure: the intrinsic microporosity of the zeolite framework together with mesoporosity existing within the zeolite plates and macroporosity stemming from the complex intergrown structure. Epitaxial and rotational intergrowths are commonly observed in many zeolites. We have hypothesized that by engineering the zeolite intergrowths, hierarchically organized zeolites can be constructed without the need for mesoporogens. In particular, we have focused on the MFI zeolite because it is an excellent catalyst in many industrial processes and a promising material for membrane separation. MFI zeolite that contains sinusoidal channels along the a axis interconnected with straight channels along the b axis is often formed with 908 rotational intergrowths, in which substantial (h00) faces are epitaxially overgrown on the (0k0)

A new method to prepare hyperbranched polyamine-oxide hybrid materials by means of a vapor-phase transport is developed. In this method, hybrid materials having hyperbranched amine polymers covalently bound to an oxide support are formed by exposing the oxide support to the vapor of small nitrogen-containing heterocyclic monomers, in contrast to the conventional liquid-phase method, in which the support is dispersed in an organic solution containing monomer species. The aziridine and azetidine monomers are polymerized on the surface of the oxide supports (i.e., silica and alumina), resulting in poly(ethylenimine) or poly(propylenimine) chains attached to the porous solid support. The results suggest that the hybrid materials can be prepared over a wide range of preparation conditions with organic contents comparable to or even higher than those obtained from the standard liquid-phase method. It is demonstrated that supports with more acidity result in the hybrid materials with higher organic content. Inte...