Ambient-Temperature Synthesis of New Layered AlPOs and GaPOs in Silica Gels

Abstract

A method for synthesising open-framework phosphates under less-severe conditions than those employed in conventional solvothermal processes is described. Two new layered aluminum phosphates containing pyridine and imidazole templates and their gallium analogues have been grown in silica gel at room temperature, and the structures determined by single-crystal X-ray diffraction. Crystal data: general formula (C5NH6)[M(HPO4)2(H2O)2], triclinic, space group P1̄, lattice parameters a = 6.994(1), b = 7.2208(7), c = 12.114(1) Å, α = 105.080(8), β = 104.85(1), γ = 90.39(1)° when M = Al; a = 7.056(1), b = 7.315(1), c = 12.165(1) Å, α = 105.32(1), β = 105.49(1), γ = 90.25(1)° when M = Ga. General formula (C3N2H5)[M(HPO4)2(H2O)2], monoclinic, space group C2/c, a = 21.893(1), b = 7.1830(3), c = 6.9890(5) Å, β = 104.164(5)° when M = Al; a = 22.002(2), b = 7.262(1), c = 7.047(1) Å, β = 105.11(1)° when M = Ga. The four structures are closely related and contain MO6 (M = Al, Ga) and PO4 polyhedra linked to form corrugated layers. The pyridinium or imidazolium cations occupy sites between these layers and are linked through hydrogen bonding to one or two adjacent layers, respectively.

Open-Framework Inorganic Materials

“…Several known aluminophosphates, including Al-PO 4 -5, AlPO 4 -11, and AlPO 4 -21, have also been synthesized from nonaqueous systems. [50] In many cases, however, lowdimensional AlPOs and GaPOs [51] were obtained, corresponding to several series of layered and chain solids, with P/ Al or P/Ga ratios ranging from 4/3 to 2/1, in which the interlamellar or interchain space is occupied by organic cations. In a recent examination of the formation of aluminophosphates under nonaqueous conditions, Ozin and coworkers [52] have suggested that intermediates based upon onedimensional chains could be involved in the crystallization of two-dimensional porous layers and finally the three-dimensional open-framework materials.…”

New open-framework phosphate and phosphite compounds of gallium

“…In fact, gallium is known to adopt 4-, 5-and 6-coordinations in many of the gallophosphate structures [5]. Persistent research over the years has yielded many gallophosphates that exhibit monomeric [6], one- [7,8], two- [9,10] and three-dimensional [11][12][13][14] structures with variations in the Ga:P ratios.…”

Molecular engineering of microporous crystals: (VIII) The solvent-dependence of the structure-directing effect of ethylenediamine in the synthesis of open-framework aluminophosphates

“…For example, phosphoric acid can react with piperazine to form the long-range ordered monohydrated piperazinium hydrogen phosphate and piperazinium dihydrogen phosphate (depending on the molar composition of the mixture) from the boehmite-phosphoric acid-piperazine-water synthetic system at ambient temperature [33]. Although layered aluminophosphate [Al(HPO 4 ) 2 $C 5 NH 6 $2H 2 O] can be obtained from the mixture with the molar composition of 1.0 Al(NO 3 ) 3 [34], the long-range ordered aluminophosphate is unlikely to be formed in hours. To verify this speculation, we reproduced the result (TEOS is not necessary in our reproducing experiments) and found that the XRD-detectable products started appearing two days later.…”