A dual template synthesis strategy was employed to achieve one-step design of meso- and microporous MFI nanosheet assemblies with tailored morphology, mesoporosity, and catalytic activity. A molecular template (tetrapropylammonium hydroxide, TPAOH) and a polyquaternary ammonium surfactant ([C22H45–N+(CH3)2–C6H12–N+(CH3)2–C6H13]Br2, C22–6–6) were used as cotemplates in the synthesis with a composition of 30Na2O/1Al2O3/100SiO2/10C22–6–6/xTPAOH/4000H2O/18H2SO4. By tuning the concentration of TPAOH (x) from 0 to 20, the morphology of the as-obtained MFI nanosheet assemblies changed from intertwined, to house-of-cards-like, and to dense packing plates. The N2 isotherms showed the hysteresis loop at the range of P/P 0 = 0.45–1.0 increases, reaches a maximum, and then decreases with increasing x values, indicating a systematic tailoring of the mesoporosity with TPAOH concentrations. Under strict kinetic control, the rates and apparent activation energies of the ethanol activation in zeolite nanosheet assemblies were comparable. The catalytic conversion of benzyl alcohol in mesitylene showed that the activity of as-obtained MFI zeolites increases, reaching a maximum, and then decreases with increasing x values. The consistency in the variation of morphology, mesoporosity, and catalytic activity with varying x values in the synthesis indicates TPAOH can be used as a secondary template to tailor the textural and catalytic properties of MFI nanosheet assemblies primarily guided by C22–6–6.

A comparison of selectivity in catalytic conversion of benzyl alcohol in mesitylene on hybrid lamellar-bulk MFI (HLBM) zeolite materials containing dual meso-/microporosity showed that the external Brønsted acidity in meso-/microporous MFI zeolites effectively impact on selectivity of the parallel alkylation and etherification reactions. HLBM zeolites, consisting of crystalline bulk microporous core and lamellar mesoporous shell, not only catalyzed the parallel reactions on the external environments (external surface and mesopore) but also etherification reaction in the internal environment (micropore) as illustrated by the completely suppressed alkylation and retained residual etherification reactions after 2,6-di-tert-butylpyridine (DTBP) poisoning. A systematic study of HLBM zeolites with tunable meso-/microporous domain sizes achieved by a dual template assisted synthesis revealed that parallel alkylation and etherification reactions are tailored by the tunable external surface area and external acidity of the HLBM zeolites. The external alkylation and etherification reaction rates as a function of cumulative DTBP addition suggested Brønsted acid sites with different strengths on external environments of the HLBM zeolites, which influenced the external etherification reaction, but not as significantly as the alkylation reaction. The evidence shown here for the involvement of external acidity in catalyzing parallel reactions and for the role of external acidity with variable strengths in HLBM zeolite materials extends the scope of observed catalytic behaviors of meso-/microporous zeolite materials beyond those reflecting transport effects and accessibility of acid sites.

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Organic pillared MFI zeolite has been synthesized by detemplation of diquaternary ammonium surfactant ([C 22 H 45 -N + (CH 3 ) 2 -C 6 H 12 -N + (CH 3 ) 2 -C 6 H 13 ]Br 2 , C 22-6-6 ) and intercalation of arylic silsesquioxane (1,4-bis(triethoxysilyl)benzene, BTEB) molecules between multilamellar MFI layers. The acid extraction and UV light radiation were sequentially employed for removal of C 22-6-6 surfactant located not only between MFI layers but also in the zeolite micropores. The removal of C 22-6-6 template by non-thermal calcination method prevents the condensation of external silanol groups of zeolitic layers stacked next to each other, which allows intercalation of BTEB molecules between the zeolitic layers and their successive reaction with the silanol groups to form the organic pillared zeolite structure. An amination post-treatment of the resultant zeolite sample introduced amino groups in the organic BTEB pillars. The acid sites from the zeolite framework aluminium and basic sites from the amino groups in BTEB pillars endow organic pillared MFI bifunctionality for cascade catalytic reactions. The synthesis of organic pillared MFI is a new addition to the structural modifications of lamellar zeolite with more open structures for processing bulky molecules. The resultant inorganic-organic hybrid zeolite structure creates new opportunities for potential applications of lamellar zeolites with tailored physicochemical properties.

COMMUNICATIONThis journal is Zeolite@metal organic framework (ZSM-5@UiO-66) coreshell composite has been synthesized for the first time by solvothermal growth of UiO-66 on the surface of ZSM-5 particles. The acidity from ZSM-5 and the basicity from the amine groups in UiO-66 obtained by post-synthetic modification of the metal clusters endow ZSM-5@UiO-66 a bifunctionality for cascade reactions.

The pillared MWW (PMWW or MCM-36) and pillared MFI (PMFI) zeolites consist of a single-or near single-unit-cell thick two-dimensional (2D) zeolitic layer structure. The concentrations of external surface and pore mouth Brønsted acid sites in these zeolites were quantified by a combined dimethyl ether (DME) titration and methanol dehydration in the presence of 2,6-di-tert-butylpyridine (DTBP) or triphenylphosphine (TPP), respectively. DME can access to all Brønsted acid sites in PMFI and PMWW zeolites and thus determine the total number of acid sites. DTBP cannot access to acid sites in micropores, but on the external surface and at the pore mouth regions. In contrast, TPP can only access to acid sites on external surface. The degree of decrease in methanol dehydration rate in the presence of DTBP or TPP indicates the fraction of the sum of external surface and pore mouth acid sites and the sole fraction of external surface acid sites, respectively. The study shows that PMFI contains ~32% external surface and ~6% pore mouth acid sites, while PMWW consists of ~33% external surface and ~31% pore mouth acid sites. The individual external surface or pore mouth acid site performed distinctively in alkylation of mesitylene by benzyl alcohol reactions.

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