Synthesis And Characterization Of Metal Phosphites Microporous Materials

Materials with open-framework structures are of great interest in the past decadesdue to their rich structural chemistry and the potential applications in ion-exchange,separation and catalysis. As part of the renaissance in the study of open-frameworkmetal phosphates, a series of novel compositions of inorganic frameworks withzero-,one-, two-or three-dimensions (0D, 1D, 2D or 3D) have been prepared byusing polar organic molecules as template agents. More recently, thepseudo-pyramidal phosphite [HPO3]2-group has been investigated as a possiblereplacement for the traditional phosphate tetrahedral with great success. Compared tophosphate [PO4] 3-, the pyramidal hydrogen phosphite group [HPO3] 2-only link threeadjacent cations via P-O-M (M = metal) bonds, which might be expected to lead to anew class of compounds with interesting architectures. Since the vanadiumphosphites with piperazinium cations as structurally directing agents weresynthesized by Zubieta et al., a number of studies on the metal phosphites containingV(III), Fe(III), Co(II), Mn(II), Zn(II) and Cr(III) have been carried out. However,less exploratory work has been carried out on synthesizing the organically templatedmain block metal phosphates. Only three organically-templated main block metalBe(II), Ga(III), Al(III) phophites were prepared.In this thesis, we described the synthesis, crystal structure and some properties ofa series of block metal (Ga, In) phosphites and transition metal (V, Cd) phosphitesand summarized the rules of synthesis and compared the difference of structures andsynthesis.Under mild hydrothermal conditions, using DETA as structure-directing agent,two three-dimensional gallium phosphites (H3DETA)Ga3(HPO3)4F4 (1) andGa2(HPO3)3 (2) have been synthesized and characterized by single crystal X-raydiffraction. The construction of 3D open-framework structure in the compound 1may be viewed as the assembly of pentameric building units and HPO3 groups. Thepentameric building unit is the first be found which lead to form three types channelsalong a, b and c axis, respectively in gallium phosphite. Compound 2 is a new threedimensional open-framework with Ga/P being 2:3 which constructed by Ga2O9dimers and HPO3 groups to form 4,12-membered ring channels along [100]directions. Replacing DETA with PIP, a new three dimensional compound 3 issynthesized and the 3D anionic framework of compound 3 is constructed from twodistinct motifs, a one-dimensional tancoite chain and a single 4-ring (S4R) unit,which contains four intersecting channels running throughout the structure as 8,12-member ring channels along to the a axis and 12-member ring channels along theb and c axis, respectively. Herein, We discuss the syntheses and structural features ofthese novel compounds and the structural relationships among them. In addition, wefind that F-is a very important effect factors for the synthesis of gallium phosphites.Under mild hydrothermal synthesis conditions, we first successfully prepared threeindium phosphites with different organic amine molecules as template agents. Thecrystal structure of (C2N2H10)[In(OH)3(HPO3)] (4) is built up from InO3(OH)3octahedron and HPO3 pseudo-pyramid that share vertices. The connectivity betweenInO3(OH)3 and HPO3 units gives rise to a ladder-like chain architecture containingfused [In2P2O4] four-member rings. Compound (C4N2H12)[In2(HPO3)3(H2PO3)2] (5)displays complex three dimensional open-framework containing multi-dimensionalintersecting 8-membered ring channels. Interestingly, the one-dimensional laddersthat similar to those observed in 4 act for building unit forming three-dimensionalstructure of 5. A novel pillared layer structure of In9(H2O)6(HPO4)12(HPO3)5·7H3O(6)is the first block metal phosphate-phosphite which contains the triple-bridge pillarunit [O3In(HPO3)3InO3]. Its structure is built up by alternation of octahedral InO6 orInO5(H2O) and pseudo-pyramidal HPO3, tetrahedral PO3(OH) units to form infinite2D layers, and these layers are interconnected by sharing vertex-oxygen with[O3In(HPO3)3InO3] triple-bridge pillar units to generate a 3D open-frameworkstructure with 16-membered ring intersecting channels in a and b directions,respectively. Our investigation show that it is possible to prepare structural complexopen-framework indium phosphites possessing cavity size, limiting apertures, andframework densities rivaling those of the most open zeolites and aluminophosphatesunder appropriate reaction conditions.Using different organic amine as template agents, three dimensional open-frameworkvanadium phosphites [V2(HPO3)3(H2O)3]·H2O (7),(C4H12N2)0.5(C4H11N2)[VIII4(HPO3)7(H2O)3]·1.5H2O (8), [VIII9(HPO3)14(H2PO3)3(H2O)6] · 4H3O(9) and cadium phosphite CdHPO3 (10) wereprepared under hydrothermal conditions. It is noteworth that the compound 7, 8, and9 are new example of 3D open-framework vanadium phosphite, in which thevanadium atoms are at the +3 oxidation state exclusively. Compound 7 is a purlyinorganic framework structure. The structure of compound 8 is built up byalternation of octahedral VO6 or VO5(H2O) and pseudo-pyramidal HPO3 units toform infinite 2D layers, and these layers are interconnected by sharing vertex-oxygenwith octahedral VO6 units to generate a 3D open-framework structure with12-membered ring channels in a and b directions, respectively. The novel pillaredlayer structure of compound 9 may be viewed as building from the large V-P-Oanion layers pillared by triple-bridge pillar unit [O3V(H2PO3)3VO3] to give rise to theintersecting 16-membered ring channels along [100] and [010] directions,respectively. The syntheses of these compounds enrich the family of vanadiumphosphites. The compound 10 is the first cadium phosphite which built by Cd3O15trimers and HPO3 pseudo pyramids to form hexangonal channels along [001]direction. However, the free space within the hexangonal channel is slightly reducedbecause the terminal P-H bonds attached to P atoms extend toward the center ofhexangonal channel. So our investigations show that more and more novel cadiumphosphite will be prepared under proper conditions.In this paper, we reviewed the syntheses and structural characterization of aseries of gallium phosphites, indium phosphites, vanadium phosphites and cadiumphosphite. These results show that it is possible to prepare structural complexopen-framework metal phosphites possessing cavity size, limiting apertures, andframework densities rivaling those of the most open zeolites and aluminophosphatesby transferring different organic amines and adjusting proper reagents molarcompostions.