Syntheses And Characterizations Of Heteroatom-Substituted Aluminophosphate Molecular Sieves

Recently, the rapid development of inorganic microporous materials in the areas fields o catalysis, separation, and host/guest assembly, etc. emphasizes the strategic status of synthesis and preparation chemistry of microprous materials. Following the discovery of the aluminophosphate molecular sieves AlPO4-n (n denotes the structure type) by Wilson et al. in 1982, a large variety of open-framework aluminophosphates with different structure types have been synthesized by using organic templates or structure-directing agents (SDAs). The structures of AlPO4-n are made of the strict alternation of AlO4 and PO4 tetrahedra forming a neutral framework. The lattice Al and/or P atoms can also be partially replaced by silicon and/or other elements to generate heteroatom-containing aluminophosphate molecular sieves, as SAPOs, MAPOs, and SMAPOs( S = Si, M = metal).The isomorphic substitution of active transition metal ions, such as Ni(II), Pd(II), Mn(II), Fe(III), V(II), Co(II), etc., into the framework sites of AlPO4-n has shown promising properties in catalysis, photoluminescence, magnetism, etc. Significantly, transition-metal-substituted aluminophosphate molecular sieves are of particular interest for the design of novel single-site solid catalysts in the general quest for clean technology and green chemistry. In contrast to their aluminosilicate zeolitic analogues, the aluminophosphate molecular sieves display advantages of enabling a variety of metallic ions to substitute isomorphously at tetrahedral sites to form single-site solid catalysts. In these single-site solid catalysts the active centers at a solid surface are spatially well separated so that an incoming species experiences the same energetic interaction between it and each one of the active centers. Such materials open up a rich range of catalytic processes for selective oxidations that can be carried out by employing single-site solid catalysts in oxygen or air.This thesis is focused on the syntheses and characterization of heteroatom -substituted aluminophosphates prepared under hydrothermal or solvothermal conditions by using organic amine as templates. A number of compounds with novel framework structures have been successfully prepared, and their syntheses, structures, and characterizations have also been investigated in detail.1. By the incorporation of transition metal ions into the aluminophosphate framework, the novel heteroatom-containing chiral aluminophosphate molecular sieves [(NH2(C2H5)2+)2][M2Al10(PO4)12] (denoted MAlPO-CJ40, M=Co, Zn) have been for the first time solvothermally synthesized by using diethylamine as the structure-directing agent. The framework has one-dimensional helical 10-ring channels and exhibits a new zeotype structure. It has been assigned as JRY (J stands for Jilin University) by international zeolite association. Notably, the metal sites can be unambiguously established by single-crystal structure analysis and molecular mechanics computation, which shows the importance of heteroatoms in stabilizing the chiral framework. Interestingly, the distribution of the metal ions along the wall of the channels shows a helical arrangement. The intrinsic symmetry of the underlying net is is I212121 with three different T sites. This means that the framework of MAlPO-CJ40 is intrinsically chiral. The vertex symbols for the three T sites in the net of MAlPO-CJ40 are 4.6.4.64.6.63, 4.63.6.62.62.62, and 4.6.6.63.63 109, respectively. This three-periodic net is carried by a unique natural tiling with the transitivity of (3 9 10 6). There are six different tiles in this tiling, with the face symbols [4.62], [63], [42.62], [62.102], and two with [6.102]. The signature of this tiling is 2[4.62]+2[63]+4[6.102]+[42.62]+[62.102]. Significantly, the CD spectrum of CoAPO-CJ40 in KBr pellet exhibits a strong Cotton effect, suggesting that the resultant crystals are not racemic although the synthesis did not involve any chiral starting materials. To date, chiral zeolites are far from complete experimental exploration yet. We have also systematically studied the factors affecting the enantiomeric excess of the chiral product. The chiral addition to the achiral synthesis system is an effective route for promoting the enantiomeric excess. The discovery of chiral AlPO-type single-site solid catalyst will open up many new applications in the fine-chemical and pharmaceutical industries.2. Three transitional metal-substituted aluminophosphate molecular sieves |(C3N2H5)8|[M8Al16P24O96] (denoted MAlPO-LAU, M = Co, Mn, Zn), with the zeotype LAU structures, have been first synthesized solvothermally in the presence of imidazole as the structure-directing agent. Their structures are determined by single-crystal X-ray diffraction and further characterized by powder X-ray diffraction (XRD), inductively coupled plasma (ICP), thermogravimetric (TG), and diffuse reflectance spectroscopy (UV-Vis) analyses. The structure of MAlPO-LAU is based on the strict alternation of MO4/AlO4 tetrahedra, and PO4 tetrahedra through vertex oxygen atoms to form the 3-D open frameworks, in which 33.3% of the aluminum sites are replaced by transitional metal ions. This substitution is determined by the host-guest charge-density matching. The protonated imidazole cations resided in the 10- ring channels. MnAlPO-LAU shows weak antiferromagnetic interaction between the Mn2+ ions in the framework. All of the MAlPO-LAU compounds show photoluminescent property due to the existence of imidazole molecules in the frameworks. Crystal data: CoAlPO-LAU, monoclinic, C2/C (No. 15), a = 14.718(3) ?, b = 13.063(3) ?, c = 15.229(3) ?,β= 110.92(3)o and Z = 8; ZnAlPO-LAU, monoclinic, C2/C (No. 15), a = 14.733(3) ?, b = 13.079(3) ?, c = 15.210(3) ?,β= 110.99(3)o and Z = 8; MnAlPO-LAU, monoclinic, C2/C (No. 15), a = 14.877(9) ?, b = 13.063(3) ?, c = 15.419(1) ?,β= 110.74(5)o and Z = 8. The transition metal-substituted aluminophosphate molecular sieves are promising materials in optics and magnetism, as well as in catalysis as important single-site solid catalysts.3. A series of transition metal substituted aluminophosphate molecular sieves including Co(Zn)-JRY, Co(Zn)-CHA and Co(Zn)-AEL have been synthesized under microwave irradiation and conventional oven heating condition with diethylamine as the template and the mixture of tetraethylengykol and water as the solvent. The influence of the heating method, amount of water in the mixed solvent, and the reaction time on the crystallization behavior of the resulting products was studied. Under conventional oven heating condition, high concentration of water in the mixed solvent favors the formation of dense phase of trydmite instead of the less dense phase of Co(Zn)-JRY which is formed from the mixed solvent with low concentration of water. In contrast to the conventional oven heating condition, the microwave irradiation heating condition promoted the crystallization of less dense phases of Co(Zn)-JRY, Co(Zn)-CHA, and Co(Zn)-AEL from the starting reaction gel with same composition. Under microwave irradiation heating condition, the prolongation of the reaction time resulted in the crystallization of Co(Zn)-CHA, Co(Zn)-JRY, and Co(Zn)-AEL, respectively. The framework densitys (FD) for the structure type of CHA, JRY, AEL are 15.1T/1000?3, 18.1T/1000?3 and 19.1T/1000?3, respectively. Thus, the formation of desired structure type of CHA, JRY, or AEL can be controlled by controlling the reaction time. The possible role of the water molecules under microwave irradiation heating condition was discussed as well. The result is useful for the rapid controllable synthesis of molecular sieves with special structure and property.In summary, this thesis is mainly focused on the syntheses of heteroatom -substituted aluminophosphates. A number of four-connected three dimensional zeolite materials with various structure architectures have been successfully prepared. This research will be important for the design and synthesis of heteroatom -substituted aluminophosphate-type single-site solid catalyst, which will open up many new applications in the fine-chemical and pharmaceutical industries.