A Review on the Synthesis and Applications of Mesostructured Transition Metal Phosphates

Abstract

Considerable efforts have been devoted to extending the range of the elemental composition of mesoporous materials since the pioneering work of the M41S family of ordered mesoporous silica by Mobil researchers. The synthesis of transition metal-containing mesostructured materials with large surface area and high porosity has drawn great attention for its potential applications in acid and redox catalysis, photocatalysis, proton conducting devices, environmental restoration and so on. Thus, various transition metals-containing mesoporous materials, including transition metal-substituted mesoporous silicates, mesostructured transition metal oxides and transition metal phosphates (TMP), have been documented in the literature. Among these, mesostructured TMP materials are less studied, but possess some unique features, partly because of the easy and facile functionalization of PO₄ and/or P-OH groups, rendering them interesting functional materials. This review first introduced the general synthesis strategies for manufacturing mesostructured TMP materials, as well as advantages and disadvantages of the respective method; then, we surveyed the ongoing developments of fabrication and application of the TMP materials in three groups on the basis of their components and application fields. Future perspectives on existing problems related to the present synthesis routes and further modifying of the functional groups for the purpose of tailoring special physical-chemical properties to meet wide application requirements were also provided in the last part.

Keywords: application; mesostructure; synthesis method; transition metal phosphate.

Figure 1

Procedures for soft-templating synthesis strategy: (a) liquid-crystal templating mechanism and (b) cooperative formation mechanism. M, P and MP represent metal, phosphorus and metal phosphates, respectively (Reprinted with permission from [15]. Copyright 1992 American Chemical Society).

Figure 2

Representative scheme for hard-templating synthesis strategy (reprinted with permission from [45]. Copyright 2005 Royal Society of Chemistry).

Figure 3

Transmission electron microscope (TEM)/scanning electron microscope (SEM) images of mesoporous ZrP materials. (a–c) Porous mesostructured zirconium oxophosphate with cubic symmetry synthesized by C18BDAC surfactant-assisted precipitation (reprinted with permission from [63]. Copyright 2002 American Chemical Society). (a) The High-resolution transmission electron microscopy (HRTEM) image taken along the [111] zone axis; (b) The electron diffraction pattern; (c) The Fourier diffractogram obtained from the HRTEM image in the labeled rectangular area; (d,e) Hierarchically nanostructured porous ZrP synthesized by Brij 56 (C₁₆(EO)₁₀ assisted self-assembly (reprinted with permission from [68]. Copyright 2005 Elsevier); (f) Mesoporous ZrP with spherical particles morphology, prepared by sequential precipitation-hydrothermal procedure in basic medium (reprinted with permission from [72]. Copyright 2006 Elsevier); (g) Hexagonally packed porous ZrP derived from anion exchange between zirconium oxide mesophase and phosphoric acid (reprinted with permission from [61]. Copyright 2005 American Chemical Society); (h,i) Ordered mesoporous ZrP films obtained by spin coating and vapor treatments (reprinted with permission from [7]. Copyright 2006 American Chemical Society).

Figure 4

TEM/SEM/AFM (Atomic force microscope) images of mesoporous TiP materials. (a) Mesoporous titanium oxo phosphate with a disordered structure synthesized by using a low-cost industrial polyethylenoxide named Dodecanol +5 EO (BASF ) as a non-ionic surfactant (reprinted with permission from [76]. Copyright 1999 Elsevier); hexagonal structured ZrP materials fabricated with the assistance of surfactants (b) C₁₈TAB and (c) C₁₆TAB (reprinted with permission from [77]. Copyright 2000 Elsevier); (d) Mesoporous TiP prepared by reaction between phosphoric acid solution and titanium chloride in the presence of trimethylammonium surfactants (reprinted with permission from [74]. Copyright 2000 Royal Society of Chemistry); (e) TCM-7 and (f) TCM-8 with poorly ordered two-dimensional hexagonal mesophase, synthesized by surfactant-assisted assembly (reprinted with permission from [37]. Copyright 2001 American Chemical Society); (g,h) Hierarchical TiP materials with multiple porosities of different lengths (meso-macroporous and meso-macro-macroporous) derived from a self-formation process [(Ti(OC₃H₇)₄-Brij 56-H₃PO₄] (reprinted with permission from [79]. Copyright 2006 American Chemical Society); (i) Mesoporous TiP with unique lamellar structures and mesopores on the surfaces fabricated by a yeast cell-assisted bio-templating route (reprinted with permission from [80]. Copyright 2011 Springer). Mesostructured TiP materials with various morphologies, prepared by a C₁₆TAB-assisted hydrothermal process at different temperatures (j) room temperature; (k) 348 K and (l) 373 K (reprinted with permission from [78]. Copyright 2007 Elsevier).

Figure 5

TEM/SEM images of mesoporous iron (a–e), vanadium (f–i) and nickel phosphates (j–m) synthesized by various methods. (a) Ordered mesostructured FeP prepared with the HF assembly method (reprinted with permission from [97]. Copyright 2007 American Chemical Society); (b) Nanotubular and mesoporous FeP synthesized in a modified fluoride route with the aid of sodium dodecyl sulfate (SDS) (reprinted with permission from [86]. Copyright 2007 American Chemical Society); (c) Amorphous FeP nanowires derived from a M13 virus-based bio-assembly (reprinted with permission from [89]. Copyright 2011 Royal Society of Chemistry); (d,e) Amorphous mesoporous FeP particles prepared by a cost-effective electrochemical method without a surfactant (reprinted with permission from [55]. Copyright 2012 Elsevier); (f) Hexagonal mesostructured oxovanadium phosphates, ICMUV-2, synthesized by Surfactant templating (CTAB)-directing assembly (reprinted with permission from [90]. Copyright 1999 American Chemical Society); (g) Lamellar (VO)₂P₂O₇ crystals obtained by pyrolysis of ICMUV-2 under N₂ ambience at 973 K (reprinted with permission from [90]. Copyright 1999 American Chemical Society); (h) Lamellar- and (i) hexagonal-mesostructured VP materials synthesized by assembling exfoliated VOPO₄ sheets using CTAB as the cationic surfactants (reprinted with permission from [92]. Copyright 2005 Elsevier); (j) Spherical NiP nanoparticles with mesopores synthesized by a hydrothermal procedure (reprinted with permission from [95]. Copyright 1993 Elsevier); (k) NiPO-1 and (l) NiPO-2, with nanotubular structures, derived from sol-gel method (reprinted with permission from [96]. Copyright 2008 Royal Society of Chemistry); (m) HPNP-1 synthesized via a surfactant-free hydrothermal method (reprinted with permission from [10]. Copyright 2012 Elsevier).

Figure 6

Ternary phase diagrams of the structures obtained in the synthesis of (a) NiPO-1; (b) NiPO-2 (reprinted with permission from [96]. Copyright 2008 Royal Society of Chemistry).

Figure 7

TEM/AFM images of mesoporous transition metal phosphates materials. (a) Less ordered mesoporous chromium phosphate (CrP) prepared by ball milling (reprinted with permission from [99]. Copyright 2012 Royal Society of Chemistry); (b) Zinc phosphate (ZnP) nanoparticles synthesized by bio-assembly (reprinted with permission from [103]. Copyright 2009 Elsevier); (c) Niobium oxophosphates (NbP) with wormhole-like morphologies prepared by tetradecyltrimethylammonium bromide (TTBr)-assisted precipitation (reprinted with permission from [100]. Copyright 2009 Elsevier); (d) Amorphous tantalum phosphate (TaP) synthesized via a sequential precipitation-hydrothermal treating technique (reprinted with permission from [104]. Copyright 2010 Elsevier); (e) Cubic ordered mesoporous yttrium phosphates (YP)-derived by nanocasting with KIT-6 as a hard template (reprinted with permission from [12]. Copyright 2009 Royal Society of Chemistry); (f) Mesoporous YP with lenticular morphology, prepared by microwave-assisted precipitation (reprinted with permission from [11]. Copyright 2012 American Chemical Society).