Hydro-Ionothermal Synthesis of Lanthanide-Organic Frameworks with 1,4-Phenylenebis(methylene)diphosphonate

Abstract

A synthetic approach combining hydrothermal and ionothermal (eutectic mixture of choline chloride and malonic acid) procedures is proposed that allowed the isolation of the first lanthanide-organic frameworks with residues of 1,4-phenylenebis(methylene)-diphosphonic acid (H 4 pmd), [Ln(Hpmd)(H 2 O)] (where Ln 3+ ) Ce 3+ and Pr 3+ ), exhibiting an unprecedented trinodal topology with 3-and 8-connected nodes. The structural details were unveiled from single-crystal X-ray diffraction and the materials were characterized using standard techniques.Metal-organic frameworks (MOFs) are an attractive class of materials that has received a considerable amount of worldwide attention over the last two decades. 1 This surge has been primarily motivated by their intriguing structural architectures 2 and, more recently, from their potential applications. 3 Remarkably, the most widely employed synthetic strategy is the solvo(hydro)thermal method inherited from zeolite chemistry. More recently, ionothermal synthesis has been used with great success to isolate novel MOFs or coordination complexes, 4-6 zeolites 7 and nanomaterials. 8 Depending on the choice of ionic liquids (ILs) different materials can be isolated and, to date, 1-ethyl-3-methyl imidazolium bromide (EMIm-Br) is the most commonly employed IL solvent and structure-directing agent (SDA). 4 However, the corresponding cation is usually included in the final product to balance the crystal charge and its removal usually implies a destruction of the framework. Following our interest in the synthesis and structural characterization of MOFs, 9 in particular those with lanthanides, here we wish to describe a simple and effective method that combines hydrothermal and ionothermal synthetic concepts (hydro-ionothermal synthesis, HI): eutectic mixtures of choline chloride and malonic acid (CM, melting point 10°C) 10 having a small amount of intentionally added distilled water were used as the solvent media in the reaction of lanthanide ions with a bisphosphonic acid source. CM mixtures have been profitably used in the preparation of a number of d-block oxalophosphates and oxalo-phosphonates, 6 but their use with lanthanides and flexible chelating ligands is unknown to date.The reaction between tetraethyl-p-xylylenebisphos-phonate (texbp) and LnCl 3 · 6H 2 O (Ln 3+ ) Ce 3+ and Pr 3+ ) in preprepared homogeneous eutectic mixtures of CM, 11 led to the isolation of phase-pure crystalline materials which were formulated as [Ln(Hpmd)(H 2 O)] (where Ln 3+ ) Ce 3+ for 1 and Pr 3+ for 2; H 4 pmd ) 1,4-phenylenebis(methylene)diphosphonic acid, see Scheme 1) on the basis of single-crystal X-ray diffraction studies 12 and CHN elemental composition studies in combination with EDS data. Even though a handful of frameworks with d-and p-block elements and H 4-x pbp -x residues have been reported, 13-16 the compounds described here constitute the first examples of framework materials with this ligand coordinated to lanthanide centers. The bulk materials are highly crystalline even tho...

Lanthanide N,N′-piperazine-bis(methylenephosphonates) (Ln=La, Ce, Nd) that display flexible frameworks, reversible hydration and cation exchange

“…These have structures in which the chloride anions reside within the pores, directing the framework configuration by their hydrogen-bonding interactions. Lanthanide phosphonates and phosphonate-carboxylates themselves make up a growing class of solids, including open framework materials that display both porosity and luminescence, and are described in a comprehensive review by Mao [17] and more recent publications [18][19][20][21].…”

catena-Poly[[triaquachlorido-μ3-malonato-cerium(III)] hemihydrate]

“…Data collection: APEX2 (Bruker, 2006); cell refinement: SAINT-Plus (Bruker, 2005); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: DIAMOND (Brandenburg, 2009) (Shi et al, 2008). Following our continuous interest in the preparation and study of the properties of metal-organic frameworks based on phosphonates (Cunha-Silva et al, 2009;Cunha-Silva et al, 2007;Paz et al, 2005;Paz et al, 2004), and our recent motivation to employ microwaves as an alternative heating source (Klinowski et al, 2010), we decided to test the afore- Table 1), the Ce1-Cl1 bond is considerably longer [2.9086 (6) Table 2).…”

“…The title compound was prepared following the procedure described elsewhere (Shi et al, 2008), while replacing hydrothermal heating by microwave heating (Klinowski et al, 2010). The reactive homogeneous suspension was transferred to a 10 ml IntelliVent reactor which was placed inside a CEM Focused Microwave TM Synthesis System Discover S-Class equipment.…”

“…For previous research from our group on coordination compounds of phosphonates, see: Cunha-Silva et al (2007 ;Shi et al (2008); Paz et al (2004Paz et al ( , 2005. For general background to the synthesis of coordination polymers using microwave heating, see: Klinowski et al (2010).…”

Synchrotron powder structure of a new layered lanthanide-organic network

“…These novel functional layered materials result from our on-going efforts toward the synthesis and structural characterisation of multidimensional LnOFs [23][24][25][26][27][28][29][30][31][32]. For example, we have recently reported a series of photoluminescent layered LnOFs, [Ln(H 3 NMP)] Á 1.5(H 2 O) [Ln 3þ ¼ La 3þ , Pr 3þ , Nd 3þ , Sm 3þ or Eu 3þ ; H 3 NMP 3À is a residue of nitrilotris(methylenephosphonic acid)], containing a triphosphonic acid ligand [31].…”