Influence of alkalinity on the synthesis of hierarchical LTA zeolite by using bridged polysilsesquioxane

The mechanism of formation of hierarchical LTA zeolite involved the methoxyl groups of bridged polysilsesquioxane hydrolyzing into hydroxyl groups. The covalent Si–O–Si bond between silicon hydroxyl in the above solution and other silica sources forms by dehydration, avoiding phase separation. The influence of alkalinity on the synthesis of hierarchical LTA zeolites was investigated by using bridged polysilsesquioxane. XRD patterns indicate the synthesis of sodalite at the same molar composition of the hierarchical LTA zeolites without bridged polysilsesquioxane. The characterization results from TG and DTG revealed that bridged polysilsesquioxane was successfully incorporated into the as-synthesized hierarchical LTA zeolite. N₂-adsorption/desorption results proved that mesopores and the porosities of the hierarchical LTA zeolites are adjustable by a change of alkalinity. SEM images indicated that the morphologies of the hierarchical LTA zeolites changed with increasing alkalinity. The hierarchical LTA zeolites showed faster initial exchange rates of Na⁺ to Mg²⁺ compared with conventional LTA.

The mechanism of formation of hierarchical LTA zeolite involved the methoxyl groups of bridged polysilsesquioxane hydrolyzing into hydroxyl groups. The Si–O–Si bond was formed between silicon hydroxyl and silica by dehydration, avoiding phase separation.     

Protective dissolution: generating secondary pores in zeolite by mechanochemical reaction

Introduction of meso-/macropores into the intrinsic microporous framework of zeolites has raised substantial interest in catalytic reactions with bulky reactants. Herein, we report the formation of secondary meso-/macropores in Silicalite-1 zeolite by a solvent-free mechanochemical grinding process. The strategy allows the preservation of high crystallinity and microporosity of the pristine zeolite, and the generation of mesopores at room temperature and marcopores at higher temperatures. The roles of the tetrapropylammonium bromide (TPABr) and ammonium fluoride (NH₄F) have been proposed and demonstrated. A protective layer is formed by TPA⁺ ions bonded with the surficial defects to shield the outer surface from the direct attack by F⁻. Instead, F⁻ diffuses into the micropore system in a local aqueous environment within zeolite formed by the mechanochemical reaction. As a result, freely diffused F⁻ selectively dissolves zones with structural defects to form secondary pores inside the zeolite. Moreover, this strategy proves highly effective in encapsulation of nanoparticles (Pt, Co) in the meso-/macropores of Silicalite-1 zeolite, forming a yolk–shell composite catalyst for potential applications.

A novel strategy for meso-/macropores formation in zeolites by mechanochemical reaction.     

Phosphorus removal and mechanisms by Zn-layered double hydroxide (Zn-LDHs)-modified zeolite substrates in a constructed rapid infiltration system

This work presents novel materials, ZnFe-LDHs-modified (Zn²⁺ : Fe³⁺ molar ratio of 2 : 1 and 3 : 1) and ZnAl-LDHs-modified (Zn²⁺ : Al³⁺ molar ratio of 2 : 1 and 3 : 1) zeolites, which were synthesized under alkaline conditions via a co-precipitation method and coated in situ on original zeolites. The as-prepared LDHs-modified zeolites were used as substrates for a constructed rapid infiltration system (CRIS) to conduct purification experiments to investigate the phosphorus removal performance of all types of zeolites. The experimental results showed that the phosphorus removal rates of the Zn-LDHs-modified zeolites reached over 80%, which are superior to that of the original zeolites. Furthermore, isothermal adsorption and adsorption kinetic experiments were conducted to explore the adsorption mechanisms. The theoretical maximumadsorption capacities were efficiently enhanced owing to the Zn-LDHs coating strategy. Especially, that of the ZnFe-LDHs-modified (3 : 1) zeolites reached 434.78 mg kg⁻¹, which is much higher than that of the original zeolites. Meanwhile, according to the fitting results of the adsorption kinetics experiments, it was found that the predominant adsorption type of the original zeolites was converted from intrinsically weak physical adsorption into more stable chemical adsorption by the Zn-LDHs coating. Furthermore, high-throughput sequencing was also exerted to uncover the phosphorus removal mechanism by microorganisms. The obtained results indicate that the relative abundance of Pseudomonas and Dechloromonas, which are closely related to phosphorus removal, effectively increased. Overall, the Zn-LDHs-modified zeolites improved the phosphorus removal performance efficiently and sustainably when applied in CRIS.

The Zn-LDHs-modified zeolites were synthesized and used as substrate of CRIS to remove phosphorus from wastewater by adsorption, interception, ion exchange and microbial action, which have outstanding performance than original zeolite.     

Optimized cesium and potassium ion-exchanged zeolites A and X granules for biogas upgrading

Partially ion-exchanged zeolites A and X binderless granules were evaluated for CO₂ separation from CH₄. The CO₂ adsorption capacity and CO₂-over-CH₄ selectivity of binderless zeolites A and X granules were optimized by partial exchange of cations with K⁺ and Cs⁺, while retaining the mechanical strength of 1.3 MPa and 2 MPa, respectively. Single gas CO₂ and CH₄ adsorption isotherms were recorded on zeolites A and X granules and used to estimate the co-adsorption of CO₂–CH₄ using ideal adsorbed solution theory (IAST). The IAST co-adsorption analysis showed that the partially ion-exchanged binderless zeolites A and X granules had a high CO₂-over-CH₄ selectivity of 1775 and 525 respectively, at 100 kPa and 298 K. Optimally ion-exchanged zeolite X granules retained 97% of CO₂ uptake capacity, 3.8 mmol g⁻¹, after 5 breakthrough adsorption–desorption cycles while for zeolite A ion-exchanged granules the reduction in CO₂ uptake capacity was found to be 18%; CO₂ uptake capacity of 3.4 mmol g⁻¹. The mass transfer analysis of breakthrough experimental data showed that the ion-exchanged zeolite X had offered a higher mass transfer coefficient, (κ) through the adsorption column compared to zeolite A; 0.41 and 0.13 m s⁻¹ for NaK_4.5Cs_0.3X and CaK_2.5Cs_0.2A, respectively.

Ion exchange of binderless zeolite A and X granules leads to high CO₂/CH₄ selectivity and CO₂ uptake capacity.     

Synthesis and characterization of a single phase zeolite A using coal fly ash

Zeolitization of coal fly ash (CFA) provides a potential alternative for creating high-added-value products from this hazardous solid waste. In this work, a single phase zeolite A with high crystallinity was successfully synthesized from CFA via the alkali fusion hydrothermal method. X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray fluorescence (XRF), Fourier transform infrared (FT-IR) spectroscopy, N₂ physisorption, and solid-state MAS NMR spectra were applied to characterize as-synthesized zeolites. Results indicated that the type and purity of zeolite were closely related to the synthesis conditions and parameters. A well-defined cubic shape of zeolite A with a specific surface area of 43.7 m² g⁻¹ was obtained at a low temperature of 75 °C during hydrothermal treatment for 18 h. The ammonium cation exchange capacity (CEC) test showed an impressive value of 232.2 mmol 100 g⁻¹ over prepared zeolite A, which was about 22 times that of the original CFA and close to commercial zeolite A. These results pave the way for the exploitation and utilization of the CFA.

A single phase zeolite A with high CEC and crystallinity was synthesized by a simple hydrothermal method at low temperature.     

Improving the hydrothermal stability of zeolite Y by La3+ cation exchange as a catalyst for the aqueous-phase hydrogenation of levulinic acid

La³⁺ cation exchange is shown to improve the hydrothermal stability and catalytic activity of bifunctional zeolite Pt/Y catalysts in the aqueous-phase hydrogenation of levulinic acid (LA) with formic acid (FA) as hydrogen source. La³⁺ cation exchange of zeolite Y (n_Si/n_Al = 16) was conducted both in aqueous solution and in the solid state. The hydrothermal stability of La³⁺-containing zeolite Y probed by exposure to the reaction mixture (0.2 mol L⁻¹ LA, 0.6 mol L⁻¹ FA) at 473 K under autogenous pressure for 24 h improves with increasing La content. The material exhibiting the highest La content (0.5 mmol g⁻¹) is the most stable with a preservation of 25% of the initial specific micropore volume after the hydrothermal treatment, whereas unmodified zeolite Y completely loses its microporosity. A new procedure using DRIFTS is a useful supplementary tool for quantifying the framework degradation of Y-type zeolites after hydrothermal treatment. Bifunctional Pt/Y catalysts after La³⁺ cation exchange are more active than the parent Y-zeolite for the hydrogenation of LA to γ-valerolactone (GVL), with significant enhancements in LA conversion, i.e., 94% vs. 42%, and GVL yield, i.e., 72% vs. 34%., after 24 h.

La³⁺ cation exchange is shown to improve the hydrothermal stability and catalytic activity of bifunctional zeolite Pt/Y catalysts in the aqueous-phase hydrogenation of levulinic acid (LA) with formic acid (FA) as hydrogen source.     

Nanoceria-modified platinum supported on hierarchical zeolites for selective alcohol oxidation

The highly selective oxidation of alcohols to aldehydes has been achieved due to the synergic effect of Pt and CeO₂ supported on hierarchical zeolites. The combination of Pt and CeO₂ strongly enhances the catalytic performance of the oxidation of benzyl alcohol to benzaldehyde with respect to the isolated materials. In addition, the hierarchical zeolite not only increases the fraction of exposed active sites because of its high surface area that can prevent the aggregation of Pt and CeO₂ nanoparticles, but also affects the oxidation state of cerium. The presence of a high content of trivalent Ce species (Ce³⁺) on the hierarchical zeolite benefits the oxidation reaction, eventually leading to almost 100% yield of an aldehyde product. Moreover, the catalytic performance can be further improved by the easily tunable Si to Al ratio of zeolite catalysts.

Illustration of Pt/CeO₂ supported on hierarchical zeolites promoting the highly selective oxidation of benzyl alcohol to benzaldehyde.     

Preparation of CuHY catalyst via solid-state ion exchange method and its catalytic performance in isobutane/2-butene alkylation

CuHY samples prepared by solid-state ion exchange of HY zeolite with CuCl were used as catalysts in isobutane/2-butene alkylation. The results show that both the addition amount of CuCl and the calcination temperature affect the ion exchange degree. Cu⁺ can be introduced into Y zeolite by replacing H⁺ in the HY zeolite after the solid-state ion exchange, causing a decrease of the amount of Brønsted acid sites and an increase of that of Lewis acid sites. When taking CuHY as the catalyst in isobutane/2-butene alkylation, the 3d¹⁰4s⁰ valence electron configuration of Cu⁺ makes it favorable for inhibiting the oligomerization of 2-butene and accelerating the hydride transfer reaction rate by indirectly increasing the local isobutane/olefin ratio around the acid sites of the catalyst. As a result, the selectivity of C8 and trimethylpentanes over CuHY in alkylate are improved compared with those of HY.

CuHY prepared by solid-state ion exchange of HY zeolite with CuCl was used as a catalyst in isobutane/2-butene alkylation. The selectivity of C8 and trimethylpentanes over CuHY in alkylate are improved compared with those of HY.     

Methane adsorption and methanol desorption of copper modified boron silicate

Boron silicate (BS) with a chabazite framework structure was synthesised using a direct route and rigorously characterized before it was ion-exchanged with copper to form Cu-BS. Employing in situ infrared spectroscopy, we show that Cu-BS is capable of oxidising methane to methoxy species and methanol interacts with the boron sites without deprotonation.

Boron silicate (BS) with a chabazite framework structure was synthesized and ion-exchanged with copper to form Cu-BS which was capable of oxidizing methane to methoxy species.     

Core–shell magnetic nano-powders with an excellent decolorization effect on dye wastewater

In recent years, zero-valent nano-iron (nZVI) has received extensive attention due to its excellent decolorization effect on dye wastewater. In this paper, zero-valent nano-iron-nickel (nZVIN) powders were prepared by a simple, efficient and non-polluting method. The powder has a unique core–shell structure and excellent oxidation resistance. Hence the problem that nZVI powders are easily oxidized and difficult to store is solved. Due to the addition of Ni, the magnetic properties of the nZVIN powders are enhanced, which facilitates the recycling of the powders using a magnetic field after sewage treatment. In the decolorization treatment of dye wastewater simulated with Congo red (CR) dye, nZVIN powders can maintain a removal rate of more than 90% for CR solutions with different pH values (7.0–11.5) and an initial dye concentration (50–200 mg L⁻¹). The research results show that nZVIN powders have broad application prospects in the treatment of azo dye wastewater.

In recent years, zero-valent nano-iron (nZVI) has received extensive attention due to its excellent decolorization effect on dye wastewater.     

Creation of Mo/Tc@C60 and Au@C60 and molecular-dynamics simulations

The formation of middle- and/or high-weight atom (Mo, Au)-incorporated fullerenes was investigated using radionuclides produced by nuclear reactions. From the trace radioactivities of ⁹⁹Mo/^99mTc or ¹⁹⁴Au after high-performance liquid chromatography, it was found that the formation of endohedral and/or heterofullerene fullerenes in ⁹⁹Mo/^99mTc and ¹⁹⁴Au atoms could occur by a recoil process following the nuclear reactions. Furthermore, the ^99mTc (and ¹⁹⁴Au) atoms recoiled against β-decay remained present inside these cages. To confirm the produced materials experimentally, ab initio molecular dynamics (MD) simulations based on an all-electron mixed-basis approach were performed. The possibility of the formation of endohedral fullerenes containing Mo/Tc and Au atoms is verified; here, the formation of heterofullerenes is excluded by MD simulations. These findings suggest that radionuclides stably encapsulated by fullerenes could potentially play a valuable role in diagnostic nuclear medicine.

The formation of Mo, Au-incorporated fullerenes was investigated using radionuclides produced by nuclear reactions and using AIMD simulations. The possibility of the formation of endohedral fullerenes containing Mo/Tc and Au atoms is verified.     

Rapid hydrothermal synthesis of hierarchical ZSM-5/beta composite zeolites

An innovative hydrothermal method has been successfully applied to the synthesis of hierarchical ZSM-5/beta composite zeolites with different mass ratios. Firstly, the ZSM-5 zeolites were coated with amorphous silica and aluminum species by a spray drying process. Then, the precursor powder was hydrothermally crystallized for only 1–2 days with the addition of tetraethyl ammonium hydroxide (TEAOH). The obtained products were characterized by XRD, SEM, TEM, N₂ physical adsorption–desorption, ²⁷Al MAS NMR, ICP, pyridine-IR and NH₃-TPD techniques. The characterization results imply that the ZSM-5/beta composite zeolites exhibit hierarchical-pores, higher external surface areas and larger mesopore volumes as compared to those of the pure ZSM-5 and beta zeolite. Moreover, the pore structure and acid sites of the ZSM-5/beta composite can be adjusted by changing the mass ratio of ZSM-5/beta. Finally, the ZSM-5/beta composite catalysts exhibit good catalytic performances in the cracking of 1,3,5-triisopropylbenzene (1,3,5-TIPB).

The hierarchical ZSM-5/beta composite zeolites synthesized via an innovative hydrothermal method exhibit superior catalytic performance in the cracking of 1,3,5-triisopropylbenzene.     

Theoretical studies on carbon dioxide adsorption in cation-exchanged molecular sieves

The capture and storage of the greenhouse gas, CO₂, has attracted much interest from scientists in recent years. In this work, density functional theory (DFT) was used to study the adsorption of CO₂ in different cation-exchanged molecular sieves. The results show that for the monovalent metal (Li, Na, K, Cu) ion-exchanged molecular sieves (zeolite Y, ZSM-5, CHA and A), the adsorption capacities for CO₂ decrease in the order of Li⁺ > Na⁺ > K⁺ > Cu⁺. Cu⁺-exchanged zeolites are not suitable as adsorbents for CO₂. For the CO₂ adsorption capacities in different zeolites with the same exchanged cation, the adsorption energy decreases in the order of Y > A > ZSM-5 ≈ CHA for Li-exchanged zeolites, and ZSM-5 still has the lowest CO₂ adsorption energy for both Na- and K-exchanged zeolites. In the cation-exchanged Y zeolites with divalent metals (Be, Mg, Ca and Zn), the CO₂ adsorption performance increases in the order of Zn²⁺ < Be²⁺ < Ca²⁺ < Mg²⁺. Thus, Zn²⁺-exchanged zeolites are not suitable as adsorbents for CO₂.

Density functional theory was used to study the adsorption of CO₂ in cation-exchanged zeolite Y, ZSM-5, CHA and A. The adsorption energies and the interactions of cations on various zeolitic topologies towards CO₂ molecule was discussed.     

Direct synthesis of ultrathin FER zeolite nanosheets via a dual-template approach

The synthesis of zeolites with nanosheet morphology has been attracting extensive attention. Despite the steady progress, the direct synthesis of ultrathin nanosheets of FER zeolite with thickness of less than 10 nm is still a great challenge. Herein we report a facile synthesis of FER zeolite nanosheets (named SCM-37) by using octyltrimethylammonium chloride (OTMAC) and 4-dimethylaminopyridine (4-DMAP) as dual organic templates. The effects of synthesis parameters, including initial molar ratio of SiO₂/Al₂O₃, crystallization temperature and time were investigated. It turned out that the crystallization field of SCM-37 was narrow. A two-step crystallization method was utilized to obtain pure and completely crystallized SCM-37 zeolite. SCM-37 was characterized by multiple techniques, including X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen physisorption, Fourier transform infrared (FTIR), ammonia-temperature programmed desorption (NH₃-TPD) and nuclear magnetic resonance (NMR), and compared with the conventional FER zeolite (C-FER). The two most significant features of SCM-37 are the ultrathin crystal nanosheet and extremely high external surface area. The thickness of SCM-37 along the a-axis is 4∼7 nm, while that of C-FER is over 20 nm. The external surface area reaches 198 m² g⁻¹, which is over ten times larger than that of C-FER. The catalytic performances of the FER zeolites were evaluated by the cracking of 1,3,5-triisopropylbenzene (TiPB). Although possessing a lower amount of total acid sites, SCM-37 showed higher conversion of TiPB, as well as selectivity to the deep cracking products. The superior performance of SCM-37 was attributed to the higher external surface area arising from the ultrathin nanosheets.

SCM-37, a FER-type zeolite with ultra-thin nanosheet morphology with thickness of 4–7 nm, was directly synthesized in a dual-template system constructed with octyltrimethylammonium chloride (OTMAC) and 4-dimethylaminopyridine (4-DMAP).     

Porous sorbents for the capture of radioactive iodine compounds: a review

The number of studies on the capture of radioactive iodine compounds by porous sorbents has regained major importance in the last few years. In fact, nuclear energy is facing major issues related to operational safety and the treatment and safe disposal of generated radioactive waste. In particular during nuclear accidents, such as that in 2011 at Fukushima, gaseous radionuclides have been released in the off-gas stream. Among these, radionuclides that are highly volatile and harmful to health such as long-lived ¹²⁹I, short-lived ¹³¹I and organic compounds such as methyl iodide (CH₃I) have been released. Immediate and effective means of capturing and storing these radionuclides are needed. In the present review, we focus on porous sorbents for the capture and storage of radioactive iodine compounds. Concerns with, and limitations of, the existing sorbents with respect to operating conditions and their capacities for iodine capture are discussed and compared.

In the capture of radioactive iodine compounds by porous sorbents, concerns with, and limitations of, the existing sorbents with respect to operating conditions and their capacities for iodine capture are discussed and compared.     

Nanoporous materials with predicted zeolite topologies

An increasing number of newly synthesized materials have been found to be previously present in databases of predicted porous materials. This has been observed not only for zeolites, but also for other inorganic materials and for MOFs. We here quantify the number of synthesized zeolites that are present in a large database of predicted zeolite structures as well as the number of other inorganic crystals and MOFs present in this same database. We find a significant number of real materials are in this predicted database of zeolite-like structures. These results suggest that many other predicted structures in this database may be suitable targets for designer materials synthesis.

Topological exploration of crystal structures demonstrates the presence of known zeolites, inorganics, and MOFs in a database of predicted materials.     

On the key role of aluminium and other heteroatoms during interzeolite conversion synthesis

Interzeolite conversion, a synthesis technique for several zeolite frameworks, has recently yielded a large amount of high-performing catalytic zeolites. Yet, the mechanisms behind the success of interzeolite conversion remain unknown. Conventionally, small oligomers with structural similarity between the parent and daughter zeolites have been proposed, despite the fact these have never been observed experimentally. Moreover, recent synthesis examples contradict the theory that structural similarity between the parent and daughter zeolites enhances interzeolite conversion. In this perspective it is proposed that heteroatoms, such as aluminium, are key players in the processes that determine the successful conversion of the parent zeolite. The role of Al during parent dissolution, and all consecutive stages of crystallization, are discussed by revising a vast body of literature. By better understanding the role of Al during interzeolite conversions, it is possible to elucidate some generic features and to propose some synthetic guidelines for making advantageous catalytic zeolites. The latter analysis was also expanded to the interconversion of zeotype materials where heteroatoms such as tin are present.

The crucial roles of aluminium in driving and controlling interzeolite conversion, a useful catalyst synthesis protocol, are put under scrutiny.     

Engineering the porosity and acidity of H-Beta zeolite by dealumination for the production of 2-ethylanthraquinone via 2-(4′-ethylbenzoyl)benzoic acid dehydration

Environmentally-friendly zeolites have been used commercially to replace concentrated sulfuric acid and oleum in the alkylation reactions and dehydration of alcohols. However, moderate activity, associated with access and diffusion limitations, low intramolecular dehydration selectivity, associated with unsatisfactory acidity, and unknown reusability have hampered their industrial implementation in the dehydration of bulky 2-(4′-ethylbenzoyl)benzoic acid (E-BBA) to 2-ethylanthraquinone (2-EAQ). Herein, we have discovered that after being treated with mild HNO₃, nano-sized H-Beta zeolite showed outstanding catalytic activity, selectivity and reusability, compared with a commercial oleum catalyst. A number of techniques, such as XRD, XPS, XRF, ²⁹Si MAS NMR, ²⁷Al MQ MAS NMR, FTIR, NH₃-TPD, argon physisorption and HR-TEM, have been employed to decouple the interdependence between acidity, porosity and catalytic performance. It was found that mild HNO₃ treatment could clean out the extra-framework aluminium deposits and selectively extract the aluminium species on the outer surface of Beta zeolites, which strengthened the acidity of the Brønsted acid sites (Si(OH)Al) inside the H-Beta micropores, thus increasing the possibility of intramolecular dehydration of E-BBA. Moreover, this mild HNO₃ treatment also dredged the network of intercrystalline mesopores, alleviating the diffusion constraints. Therefore, through the dual adjustment of acidity and porosity, dealuminated H-Beta zeolite has a promising future in the green synthesis of 2-EAQ.

Mild HNO₃ treated nano-sized H-Beta zeolite showed outstanding catalytic activity, selectivity and reusability, compared with a commercial oleum catalyst.      

Synthesis and properties of zeolite/N-doped porous carbon for the efficient removal of chemical oxygen demand and ammonia-nitrogen from aqueous solution

A novel adsorbent zeolite/N-doped porous activated carbon (ZAC) was prepared by the synthesis of zeolite and mesoporous carbon to remove ammonia nitrogen (NH₄⁺–N) and chemical oxygen demand (COD) from aqueous solution. The impacts of adhesives, molding pressure, synthetic temperature and ratio on ZAC preparation were investigated. The prepared adsorbent was characterized by BET surface area measurement, scanning electron microscopy and X-ray diffraction. The adsorption kinetics was better depicted by the pseudo-second-order model than the pseudo-first-order model and the isotherm fitted well with the Langmuir model. The adsorption process was endothermic, spontaneous and favorable according to thermodynamic data. The adsorbent has much potential in the simultaneous removal of COD and NH₄⁺–N from wastewater.

A novel adsorbent zeolite/N-doped porous activated carbon (ZAC) was prepared by the synthesis of zeolite and mesoporous carbon to remove ammonia nitrogen (NH₄⁺–N) and chemical oxygen demand (COD) from aqueous solution.     

Hierarchical micro-/mesoporous zeolite microspheres prepared by colloidal assembly of zeolite nanoparticles

A novel template-free colloidal assembly method that combines colloidal zeolite (silicalite-1) suspensions in a water-in-oil emulsion with an evaporation-induced assembly process has been developed for preparing hierarchical micro-/mesoporous zeolite microspheres (MZMs). Such particles have an interconnected mesoporosity and large mesopore diameters (25–40 nm) combined with 5.5 Å diameter micropores of the zeolite nanoparticles. The method developed has the advantages of employing mild synthesis conditions, a short preparation time, and not requiring the use of a mesoporogen template or post-treatment methods. The method provides a new range of micro-/mesoporous zeolites with tunable mesoporosity dictated by the size of the zeolite nanoparticles. It also offers the possibility of combining several zeolite particle sizes or optionally adding amorphous silica nanoparticles to tune the mesopore size distribution further. It should be generally applicable to other types of colloidal zeolite suspensions (e.g. ZSM-5, zeolite A, beta) and represents a new route amenable for cost-effective scale-up.

Evaporation-driven colloidal assembly of silicalite-1 nanoparticles into well-defined micro-sized spheres at low temperature and preparation times.