NaA zeolite (Si/Al = 1.00) has been commercially applied for capturing radioactive ⁹⁰Sr²⁺ because of its high surface charge density, effectively stabilizing the multivalent cation. However, owing to its narrow micropore opening (4.0 Å), large micron-sized crystallites, and bulkiness of hydrated Sr²⁺, the Sr²⁺ exchange over NaA has been limited by very slow kinetics. In this study, we synthesized nanocrystalline low-silica X by minimizing a water content in a synthesis gel and utilizing a methyl cellulose hydrogel as a crystal growth inhibitor. The resulting zeolite exhibited high crystallinity and Al-rich framework (Si/Al of approximately 1.00) with the sole presence of tetrahedral Al sites, which are capable of high Sr²⁺ uptake and ion selectivity. Meanwhile, the zeolite with a FAU topology has a much larger micropore opening size (7.4 Å) and a much smaller crystallite size (~340 nm) than NaA, which enable significantly enhanced ion-exchange kinetics. Compared to conventional NaA, the nanocrystalline low-silica X exhibited remarkably increased Sr²⁺-exchange kinetics (> 18-fold larger rate constant) in batch experiments. Although both the nanocrystalline low-silica X and NaA exhibited comparable Sr²⁺ capacities under equilibrated conditions, the former demonstrated a 5.5-fold larger breakthrough volume than NaA under dynamic conditions, attributed to its significantly faster Sr²⁺-exchange kinetics.

Lower olefins, produced from syngas through Fischer-Tropsch synthesis, has been gaining worldwide attention as a non-petroleum route. However, the process demonstrates limited selectivity for target products. Herein, a hybrid catalyst system utilizing Fe-based catalyst and SAPO-34 was shown to enhance the selectivity toward lower olefins. A comprehensive study was conducted to examine the impact of various operating conditions on catalytic performance, such as space velocity, pressure, and temperature, as well as catalyst combinations, including loading pattern, and mass ratio of metal and zeolite. The findings indicated that the addition of SAPO-34 was beneficial for enhancing catalytic activity. Furthermore, compared with AlPO-34 zeolite, the strong-acid site on SAPO-34 was identified to crack the long-chain hydrocarbons, thus contributing to the lower olefin formation. Nevertheless, an excess of strong-acid sites was found to detrimentally impact the selectivity of lower olefins, attributed to the increased aromatization and polymerization of lower olefins. The detailed analysis of a hybrid catalyst in Fischer-Tropsch synthesis provides a practical strategy for improving lower olefins selectivity, and has broader implications for the application of hybrid catalyst in diverse catalytic systems.

A facile synthesis of hierarchical ZSM-5 with the three-dimensionally ordered mesoporosity (3DOm ZSM-5) was achieved by solid conversion (SC) of SiO₂ colloidal crystals to high-crystalline ZSM-5. The products of 3DZ5_S/C and 3DZ5_S, which were severally transformed from the carbon-padded SiO₂ colloidal crystals and the initial SiO₂ colloidal crystals, exhibited not only a similar ordered structure and acidity but also higher crystallinity and more balanced meso-/micropore combination in comparison with 3DZ5_C obtained by the conventional confined space crystallization approach. All three synthesized 3DZ5 catalysts showed improved methanol-to-propylene performance than the commercially microporous ZSM-5 (CZ5), embodied in five times longer lifetime, higher propylene selectivity and S_propylene/S_ethylene ratio (P/E), and superior coke toleration with lower formation rate of coke (R_coke). Moreover, the 3DZ5_S catalyst in situ converted from SiO₂ colloidal crystals presented the highest selectivities of propylene (42.51%) and light olefins (74.6%) among all three 3DZ5 catalysts. The high efficiency in synthesis and in situ utilization of SiO₂ colloidal crystals demonstrate the proposed SC strategy to be more efficiently and eco-friendly for the high-yield production of not only 3DOm ZSM-5 but also other types of hierarchical zeolites.

Developing hierarchical and nanoscale ZSM-5 catalysts for diffusion-limited reactions has received ever-increasing attention. Here, ZSM-5 architecture integrated with hierarchical pores and nanoscale crystals was successfully prepared via in situ self-assembly of nanoparticles-coated silicalite-1. First, the oriented attachment of amorphous nanoparticles on external surface of silicalite-1 was achieved by controlling the alkalinity of Si-Al coating solution. The partial exposure of the external surface of silicalite-1 ensured the uniform removal of silicon in the bulk phase for the creation of hierarchical pores during the subsequent desilication-recrystallization. The uniform removal of silicon species in the bulk phase was mainly due to the synergistic effect of surface protection and alkaline etching, which could be balanced by regulating the relative amount of tetrapropylammonium cation and OH^– in desilication-recrystallization solution. Importantly, the removed silicon from silicalite-1 recrystallized and in situ assembled into final ZSM-5 nanocrystals induced by surface Si-Al nanoparticles. The hierarchical pores and nanoscale crystals on this integrated architecture not only promoted the removal of coke precursors from micropores but also provided large external specific surface (91 m²·g^–1) for coke deposition. Consequently, a much longer catalytic lifetime was achieved for methanol-to-aromatics reaction compared to conventional hollow structure ZSM-5 (84 h vs 46 h), with relatively high stability.

Graphene oxide is a promising adsorption material. However, it has been difficult to recycle and separate graphene oxide in the solution. To alleviate this problem, graphene oxide was thermally reduced to produce porous hydrogel which was then functionalized with polydopamine. The functional groups act as not only adsorption sites but also nucleation sites for in situ crystallization of cobalt-doped zeolitic-imidazolate-framework-8 nano-adsorbents. The effects of cobalt-doping contents on the physicochemical and adsorption properties of the resulting aerogel were also evaluated by varying the cobalt concentration. For instance, the reduced graphene oxide-polydopamine/50cobalt-zeolitic-imidazolate-framework-8 aerogel exhibited a high surface area of 900 m²·g^–1 and maintained the structure in water after ten days. The as-synthesized aerogels showed an ultrahigh adsorption capacity of 1217 ± 24.35 mg·g^–1 with a removal efficiency of > 99% of lead, as well as excellent adsorption performance toward other heavy metals, such as copper and cadmium with adsorption capacity of 1163 ± 34.91 and 1059 ± 31.77 mg·g^–1, respectively. More importantly, the lead adsorption stabilized at 1023 ± 20.5 mg·g^–1 with a removal efficiency of > 80% after seven cycles, indicating their potential in heavy metal removal from industrial wastewater.

Electrified non-thermal plasma (NTP) catalytic hydrogenation is the promising alternative to the thermal counterparts, being able to be operated under mild conditions and compatible with green electricity/hydrogen. Rational design of the catalysts for such NTP-catalytic systems is one of the keys to improve the process efficiency. Here, we present the development of siliceous mesocellular foam (MCF) supported Cu catalysts for NTP-catalytic CO₂ hydrogenation to methanol. The findings show that the pristine MCF support with high specific surface area and large mesopore of 784 m²·g⁻¹ and ~8.5 nm could promote the plasma discharging and the diffusion of species through its framework, outperforming other control porous materials (viz., silicalite-1, SiO₂, and SBA-15). Compared to the NTP system employing the bare MCF, the inclusion of Cu and Zn in MCF (i.e., Cu₁Zn₁/MCF) promoted the methanol formation of the NTP-catalytic system with a higher space-time yield of methanol at ~275 μmol·g_cat⁻¹·h⁻¹ and a lower energy consumption of 26.4 kJ·{\mathrm{m}\mathrm{m}\mathrm{o}\mathrm{l}}_{{\mathrm{C}\mathrm{H}}_3\mathrm{O}\mathrm{H}}⁻¹ (conversely, ~225 μmol·g_cat⁻¹·h⁻¹ and ~71 kJ·{\mathrm{m}\mathrm{m}\mathrm{o}\mathrm{l}}_{{\mathrm{C}\mathrm{H}}_3\mathrm{O}\mathrm{H}}⁻¹, respectively, for the bare MCF system at 10.1 kV). The findings suggest that inclusion of active metal sites (especially Zn species) could stabilize the CO₂/CO-related intermediates to facilitate the surface reaction toward methanol formation.

Bifunctional metal/zeolite materials are some of the most suitable catalysts for the direct hydroalkylation of benzene to cyclohexylbenzene. The overall catalytic performance of this reaction is strongly influenced by the hydrogenation, which is dependent on the metal sizes. Thus, systematically investigating the metal size effects in the hydroalkylation of benzene is essential. In this work, we successfully synthesized Ru and Pd nanoparticles on Sinopec Composition Materials No.1 zeolite with various metal sizes. We demonstrated the size-dependent catalytic activity of zeolite-supported Ru and Pd catalysts in the hydroalkylation of benzene, which can be attributed to the size-induced hydrogen spillover capability differences. Our work presents new insights into the hydroalkylation reaction and may open up a new avenue for the smart design of advanced metal/zeolite bi-functional catalysts.

We report results from computational modeling of the relative stability of germanosilicate SCM-15 structure due to different distribution of germanium heteroatoms in the double four-member rings (D4Rs) of the framework and the orientation of the structure directing agent (SDA) molecules in the as-synthesized zeolite. The calculated relative energies of the bare zeolite framework suggest that structures with germanium ions clustered in the same D4Rs, e.g., with large number of Ge–O–Ge contacts, are the most stable. The simulations of various orientations of the SDA in the pores of the germanosilicate zeolite show different stability order—the most stable models are the structures with germanium spread among all D4Rs. Thus, for SCM-15 the stabilization due to the presence of the SDA and their orientation, is thermodynamic factor directing both the formation of specific framework type and Ge distribution in the framework during the synthesis. The relative stability of bare structures with different germanium distribution is of minor importance. This differs from SCM-14 germanosilicate, reported earlier, for which the stability order is preserved in presence of SDA. Thus, even for zeolites with the same chemical composition and SDA, the characteristics of their framework lead to different energetic preference for germanium distribution.

The fabrication of suitable MFI zeolites to effectively produce para-xylene through the alkylation between toluene and methanol is highly desired. Here, the two-dimensional pillared MFI zeolite was modified by silicalite-1, and its morphology and structure were systematically investigated by tuning the concentration of Si species during the secondary crystallization process. The MFI zeolites were characterized by X-ray diffraction, transmission electron microscopy, pyridine-infrared and N₂ adsorption-desorption isotherms. The characterization results showed that the external Brønsted acid sites of surface passivated P-MFI-x samples have been successfully shielded. Interestingly, the P-MFI-23 showed long lifetime and high selectivity of para-xylene (about 35%) based on the cooperation between opened interlamellar structure and passivated silicalite-1 layer. It was found that the accumulated hard coke in the interior of MFI zeolites not only blocked the channels of zeolites but also covered the acidic sites, resulting in the deactivation of catalyst. Furthermore, the highest selectivity of para-xylene (about 48%) can be achieved for P-MFI-30 under harsh reaction condition, which also exhibited excellent regeneration property in the alkylation reaction between toluene and methanol. The strategy described in present research may open a window for the design of other advanced materials.