•Aluminophosphates with the same open-framework topology were synthesized.•Their crystallization processes were investigated with multiple other techniques.•31P {27Al} PT-J-HMQC NMR was performed.•The possible starting points of crystallization were analyzed.•The role of diamines in the multi-template/one-structure phenomenon was analyzed.Microporous aluminophosphates with the same open-framework topology were hydrothermally synthesized in the presence of 1,4-butanediamine, 2-methyl-1,5-pentamethylenediamine, and 1,6-hexamethylenediamine. The crystallization processes of such materials were investigated using solid-state NMR in combination with XRD and other techniques. It was found that the crystallization rate of the initial mixture can be significantly affected by the distance between the two N atoms of the diamine. The evolution of the coordination states of the Al and P sites of the open-framework was investigated by using solid-state NMR and 31P {27Al} PT-J-HMQC NMR analyses. The possible starting points of crystallization for these aluminophosphates were analyzed, and the specific fragments required for the formation of each compound were suggested. In combination with the computational simulation, we investigated the role of the diamines in the crystallization of these microporous materials, which is known as the multi-template/one-structure phenomenon.Download high-res image (181KB)Download full-size image

Polymorph A-enriched zeolite beta was hydrothermally synthesized from an extremely concentrated system using tetraethylammonium hydroxide (TEAOH) as an organic structure-directing agent (OSDA) in the presence of fluoride. The sample was investigated by powder X-ray diffraction (XRD), 29Si magic angle spinning nuclear magnetic resonance (MAS NMR), 19F MAS NMR, and high-resolution transmission electron microscopy (HRTEM). The polymorph A enrichment was confirmed by the characterization, and the percentage of polymorph A was determined to be approximately 66% by DIFFaX simulation and HRTEM analyses. A pure polymorph A stacking area was detected by HRTEM, and the chiral structure of polymorph A in the zeolite beta was investigated on the basis of the HRTEM images.

•Polymorph A-enriched zeolite beta was synthesized with a co-template strategy.•The synthesis cost for polymorph A-enriched zeolite beta was significantly reduced.•The co-template strategy opens a new way to synthesize polymorph A-enriched beta.The initial mixture containing fully hydrolysed tetraethyl orthosilicate (TEOS) and tetraethylammonium hydroxide (TEAOH) solution was treated either by heating at 80 °C or by freeze-drying. After adding an appropriate amount of concentrated hydrofluoric acid, the resulting mixture was crystallized at 150 °C. The heating treated mixture produced polymorph A-enriched zeolite beta while freeze-drying treated mixture gave only normal zeolite beta. The 13C magic angle spinning nuclear magnetic resonance (MAS NMR) analysis and thermogravimetric analysis (TGA) indicated that a partial decomposition of TEAOH to generate triethylamine (TEA) occurred during the heating dehydration process, which was the only difference compared with the freeze-drying process. Together with the reduced TEAOH, different monoamines as a co-template directed the polymorph A-enriched zeolite beta with the freeze-drying process. Diamines as a co-template directed only the normal zeolite beta. The synthesis cost of polymorph A-enriched zeolite beta can be significantly reduced by lowering the usage of expensive TEAOH and using cheaper monoamines.

•The solvent can affect the structure-directing effect of ethylenediamine.•The crystallization processes of aluminophosphates were characterized.•The possible starting points of crystallization (core units) were suggested.•The ways how the solvent affects the structure-directing effect were investigated.By heating two mixtures with the molar composition of Al2O3:3.0 P2O5:4.0 ethylenediamine (en):90 ethylene glycol (EG):7.9 H2O and Al2O3:3.0 P2O5:4.0 ethylenediamine (en):90H2O at 180 °C, one-dimensional (1D) chain-like aluminophosphate 1 ([AlP2O8H][N2C2H10]) and three-dimensional (3D) open-framework aluminophosphate AlPO4-12 ([Al3P3O13][N2C2H10]) were obtained, respectively. The crystallization processes were investigated using powder X-ray diffraction (XRD) and solid-state magic-angle spinning nuclear magnetic resonance (MAS NMR) techniques. The evolution of the coordination state of Al and P during the crystallization was monitored. A possible starting point (core unit) for the crystallization of both structures was suggested. The correlation between the core units and the long-range ordering of the planes first appeared in the early stage of both crystallization processes were investigated. The results show that the solvent can affect the structure-directing effect of ethylenediamine by altering the type and distribution of the fragments formed in the synthetic system and the starting point (core unit) of the crystallization, which will determine the structure of the resulting crystals. The long-range ordering along the direction that is represented by the diffraction peaks which appeared earlier than other diffraction peaks during the crystallization process might be formed from a core unit.

Upon heating the same initial mixture with the composition of Al2O3:P2O5:1.5 2-methylpiperazine:125H2O at 150 and 200 °C, two layered aluminophosphates were obtained. The crystallization processes of these layered aluminophosphates were investigated using multiple techniques. The change in the pH values of the solutions, the change in the concentrations of Al and P in the liquid phases, and the evolution of the coordination states of Al and P in the solid products were monitored. The “reverse temporal evolution” analyses of each structure showed that the core units or the possible onsets (nuclei) of crystallization of each structure were significantly different from each other. The results showed that the heating temperature altered the structure-directing effect of 2-methylpiperazine and the crystallization process of the initial mixture via changing the structure and chemical properties of the structure-directing agent of 2-methylpiperazine, the equilibrium of the reactions occurring among the source materials, and the assembly of the inorganic oligomers.

Using n-propylamine as a template, deioned water and secondary-butanol (butan-2-ol) as solvents, a three-dimensional (3D) open-framework aluminophosphate [C3NH10]·[HAl3P3O13] (1) and a two-dimensional layered aluminophosphate [C3NH10]3·[Al3P4O16] (2) were crystallized from the initial mixtures with compositions of Al2O3: 2.4 P2O5: 5.0 n-propylamine: 100 H2O/butan-2-ol, respectively. They are characterized by X-ray powder diffraction (XRD), thermogravimetric (TG), and elemental (CHN) analyses and structurally determined by single-crystal X-ray diffraction analysis. Compound 1 crystallizes in the monoclinic space group P21/c with a = 0.85831(13) nm, b = 1.7677(3) nm, c = 1.04353(12) nm, β = 123.887(9)°, and V = 1.3143(3) nm3. Compound 2 crystallizes in the monoclinic space group P21/c with a = 1.1313(2) nm, b = 1.4874(3) nm, c = 1.8020(6) nm, β = 125.07(2)°, and V = 2.4817(11) nm3. The results show that the properties of solvent have a significant influence on the structure-directing effect of n-propylamine in the crystallization of the open-framework aluminophosphates.

A novel chiral open-framework fluoroaluminophosphate [C4N3H16][Al6P3O12F6(OH)6] was hydrothermally synthesized using diethylenetriamine as a structure-directing agent. The significant enantiomeric excess of the bulk product was confirmed by the solid state vibrational circular dichroism (VCD) spectrum.

The influence of water content on the crystallization of the microporous aluminophosphate AlPO4-11 was investigated by a combination of in situ UV Raman and ex situ XRD and NMR characterizations. Under high water content conditions (Al2O3:H2O = 1:20–69), an AlPO4-5 intermediated formed first and later co-existed with AlPO4-11. In the last stage of crystallization, the crystalline AlPO4-5 completely disappeared and well-crystallized AlPO4-11 was obtained. The position of the three signals observed in the 31P MAS NMR spectra of the isolated solid samples did not change during the hydrothermal treatment, suggesting that the fragments containing the P site in the junction of 6- and 4-membered rings of both AlPO4-5 and AlPO4-11 formed first and that the environments of the P sites were very similar to those in the final structure. A significant increase of Al concentration in liquid media was observed before the appearance of XRD detectable AlPO4-11. Under low water content conditions (Al2O3:H2O = 1:15), the AlPO4-11 was directly crystallized from the initial mixture. In situ Raman spectra showed that the 10-membered rings were complete by the time the transformation of octahedral Al to tetrahedral Al was finished and that the conformation of the protonated di-(i-propyl)amine changed little during the crystallization. The present study showed that the composition of the liquid phase is critical to the formation of a specific structure.Graphical abstractHighlights► Under high water conditions, an AlPO4-5 intermediate was observed for the first time. ► The position of the three signals observed in the 31P MAS NMR spectra did not change. ► A significant increase of Al concentration in liquid media was observed. ► Under low water conditions, the AlPO4-11 was directly crystallized.

The products of microporous aluminophosphate AlPO4-11 crystallized for different periods of time were freeze-dried and characterized by XRD and NMR techniques. Six crystallographically distinct Al- and P-centered large fragments and 34 small fragments of dimer (Al–P), trimer (Al–P–Al and P–Al–P), tetramer (Al–P3 and P–Al3), pentamer (Al–P4 and P–Al4), and 4- and 6-membered rings were extracted from the framework of AlPO4-11. Each of the six large fragments contained two completed coordination layers surrounding the centered atom. The shielding tensors of the Al and P atoms of the fragments were calculated using the quantum mechanics density functional theory. The experimentally observed chemical shifts of Al or P from the well-crystallized AlPO4-11 were assigned to the shielding tensors of the center atoms of the six large fragments and were further used as references in the determination of the chemical shifts of the Al or P atoms in the small fragments. A comparison of the calculated chemical shifts of the Al and P atoms in the small fragments to the experimental data of the products isolated at different crystallization periods suggested that the fragments of dimers, trimers of the form Al–P–Al, tetramers of the form P–Al3, and pentamers may exist in the crystallization process of AlPO4-11. On the basis of these observations regarding the putative small fragments, a possible crystallization process of AlPO4-11 was proposed.Graphical abstract.Highlights► Possible fragments formed in crystallization were extracted from AlPO4-11. ► Chemical shift of the small fragments were calculated. ► Calculated results were compared with the experimentally observed data. ► Sixteen small fragments that may exist in the crystallization process were identified. ► A method to identify the possible fragments formed in the synthesis is developed.

The products of piperazine-directed synthesis of two-dimensional (2D) aluminophosphates, AP2pip and AlPO-CJ9, that were crystallized under different conditions for different periods of time were freeze-dried and characterized using XRD and NMR techniques. The core units of the layered aluminophosphates including AP2pip, AlPO-CJ9, and L-DAP, which was hydrothermally synthesized in the presence of racemic 1,2-diaminopropane, were obtained by applying a “reverse evolution” process to their structures. The factors affecting the structure-directing ability of piperazine under acidic and basic conditions were analyzed. The cooperative role of water in directing the layered aluminophosphate of AP2pip under acidic conditions is discussed. After a thorough analysis of the core units of AlPO-CJ9 and L-DAP, a new phenomenon of a “topological-structure-directing effect” or a “topological-templating effect” was observed. The observation of the new phenomenon of a topological-structure-directing effect or a topological-templating effect may contribute to a deeper understanding of the nature or origin of the “structure-directing or templating effect”.Graphical abstractHighlights► The nature of structure-directing ability of piperazine was investigated. ► The crystallization process of two layered aluminophosphates was investigated. ► The factors affecting the structure-directing ability of piperazine were studied. ► The cooperative structure-directing role of water was investigated. ► A new “topological-structure-directing-effect” phenomenon was observed.

A new three-dimensional (3D) anionic interrupted open-framework aluminophosphate [(C4N2H12)3·H2O][(Al2P3O12)2] (denoted AlPO-JU88) with an Al/P ratio of 2/3 was hydrothermally synthesized by using piperazine as a structure directing agent. The structure was determined by single-crystal X-ray diffraction structural analysis and was further characterized by X-ray powder diffraction, elemental (CHN), thermogravimetric (TG), and NMR analyses. The strict alternation of Al-centered tetrahedra (AlO4) and P-centered tetrahedra (PO2(O)2 and PO3(O)) via bridging oxygen atoms resulted in a 3D open-framework featuring a new type of super-cage of 46128. Six racemic helical (31 or 32) chains were linked together to form a twelve-ring (12R) channel along the [0 0 1] direction, forming a multi-directional intersecting 12R channel system together with the 12R channels run along [2 4 1], [2 –2 1], and [− 4 − 2 1] directions. The negative charge of the framework was balanced by doubly protonated piperazine molecules. Ion exchange experiment suggested that 22 mol% of the protonated piperazine can be exchanged by Na cations, showing a better ion exchange property for the 3D interrupted open-framework aluminophosphates.The synthesis, characterization, and ion exchange study of a new 3D anionic interrupted aluminophosphate [(C4N2H12)3·H2O][(Al2P3O12)2] (denoted AlPO-JU88) with multi-directional intersecting 12R channel system, helical chains, and a new type of super-cage was reported.Highlights► A new 3D anionic interrupted aluminophosphate was hydrothermally synthesized. ► The compound contains a multi-directional intersecting 12R channel system. ► The structure features helical chains and a new type of super-cage. ► The compound shows a good ion exchange property.

A new method for the fabrication of highly b-oriented silicalite-1 films is presented. With this method, the surface of the substrate of glass slides was modified with different surface coverage of Ti–OH groups by a surface sol–gel process, which enables layer-by-layer coating of a selected metal oxide on a hydroxyl-terminated surface. The modification of the glass substrate by the TiO2 layers greatly increased the density and the reactivity of the surface hydroxyl groups. After the insitu growth under normal synthetic conditions, highly b-oriented zeolite thin films were obtained. The resulting highly b-oriented zeolite thin films were further characterized by powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM). This method offers a general, facile, and straightforward approach to the preparation of various zeolite films under normal synthetic conditions.Graphical abstractHighlights► The surface sol–gel chemistry is introduced into the synthesis and preparation of zeolite films for the first time. ► The density and reactivity of the surface hydroxyl groups of substrate are greatly increased. ► The b-oriented silicalite-1 films were prepared on surface sol–gel process modified substrate via in situ crystallization. ► This method offers a straightforward approach to the preparation of various zeolite films under normal synthetic conditions.

A new layered germanate (C4N2H12)(NH4)2[(GeO2)3(GeO1.5F3)2] (denoted JLG-2) co-templated by diprotonated piperazine cations and ammonium ions has been solvothermally synthesized. JLG-2 was characterized by powder X-ray diffraction (XRD), inductively coupled plasma (ICP), and elemental (CHN). The structure was determined by single-crystal X-ray diffraction analysis. JLG-2 crystallizes in orthorhombic, space group Pbcn (No. 60), with a = 7.1235(3) Å, b = 11.7131(5) Å, c = 20.9375(10) Å, and Z = 4. The inorganic sheet of JLG-2 was built up from alternation of tetrahedral GeO4 and octahedral GeO3F3. Propeller-like chiral structure building units of Ge5O12F6 with Δ- and Λ-configuration were present in the inorganic sheet with a topology of 3, 9-net. The helical arrays of H-bonds formed between the arrays of diprotonated piperazine cations and the chiral chains that are built from the linkage of the propeller-like chiral SBUs with same configuration via O1, which was rare in pure germanate compounds.By employing the diprotonated piperazine cations and ammonium ions as the co-templates, a novel layered germanate (C4N2H12)(NH4)2[(GeO2)3(GeO1.5F3)2] (denoted JLG-2) has been synthesized under solvothermal condition. The inorganic sheet is alternatively linked by the chiral chains with opposite chirality, which is formed by the building units Ge5O12F6 with the same configuration. And helical arrays of hydrogen-bonds were formed by the interaction between the diprotonated piperazine cations and the monochiral inorganic chains.Highlights► A new layered germanate containing helical arrays of H-bond. ► The 3,9-net sheet was constructed by propeller-like SBUs with Δ- and Λ-configuration. ► The propeller-like SBUs with same configuration linked each other to form chiral chains.

The quantitative correlation between morphology of silicalite-1 (Si-MFI) crystals and dielectric constants of solvents for the reaction system of TEOS–TPAOH-alcohol under microwave heating was investigated. The dielectric constant of the solvent was finely tuned by mixing water and additional alcohols according to the equation of εm=Φ1ε1+Φ2ε2+⋯+Φnεnεm=Φ1ε1+Φ2ε2+⋯+Φnεn. The length and fraction of Si-MFI crystals with self-stacked morphology as a function of dielectric constant was investigated, and the linear correlation was found. The self-stacked crystals were obtained when the dielectric constant of the mixed solvent was lower than 41.0, while only fully isolated crystals were formed when the dielectric constant was higher than 45.0. The regularities observed in the microwave-assisted solvothermal synthesis system were not observed in the conventional oven-heated solvothermal synthesis system.

A novel chiral open-framework fluoroaluminophosphate [C4N3H16][Al6P3O12F6(OH)6] was hydrothermally synthesized using diethylenetriamine as a structure-directing agent. The significant enantiomeric excess of the bulk product was confirmed by the solid state vibrational circular dichroism (VCD) spectrum.