Isostructural modular microporous Na2[Y(hedp)(H2O)0.67] and Na4[Ln2(hedp)2(H2O)2]‚nH2O (Ln ) La, Ce, Nd, Eu, Gd, Tb, Er) framework-type, and layered orthorhombic [Eu(H2hedp)(H2O)2]‚H2O and Na0.9[Nd0.9Ge0.10(Hhedp)(H2O)2], monoclinic [Ln(H2hedp)(H2O)]‚3H2O (Ln ) Y, Tb), and triclinic [Yb(H2-hedp)]‚H2O coordination polymers based on etidronic acid (H5hedp) have been prepared by hydrothermal synthesis and characterized structurally by (among others) single-crystal and powder X-ray diffraction and solid-state NMR. The structure of the framework materials comprises eight-membered ring channels filled with Na + and both free and lanthanide-coordinated water molecules, which are removed reversibly by calcination at 300°C (structural integrity is preserved up to ca. 475°C), denoting a clear zeolite-type behavior. Interesting photoluminescence properties, sensitive to the hydration degree, are reported for Na4[Eu2(hedp)2-(H2O)2]‚H2O and its fully dehydrated form. The 3D framework and layered materials are, to a certain extent, interconvertable during the hydrothermal synthesis stage via the addition of HCl or NaCl: of the 3D framework Na4[Tb2(hedp)2(H2O)2]‚nH2O, affords layered [Tb(H2hedp) (H2O)]‚3H2O, whereas layered [Tb(H2-hedp)(H2O)2]‚H2O reacts with sodium chloride yielding a material similar to Na4[Tb2(hedp)2(H2O)2]‚nH2O. In layered [Y(H2hedp)(H2O)]‚3H2O, noncoordinated water molecules are engaged in cooperative waterto-water hydrogen-bonding interactions, leading to the formation of a (H2O)13 cluster, which is the basis of an unprecedented two-dimensional water network present in the interlayer space.

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...

Using bulky amides as the structure-directing agents (SDAs) is an alternative synthetic strategy for the exploration of crystalline large pore (≥12-membered ring) zeolitic imidazolate frameworks (ZIFs). Specifically, by using the bulky amides, dibutylformamide (DBF) and dipropylformamide (DPF) as solvent and imidazole (Im) as a ligand, two ZIFs mimicking the CAN and AlPO-5 (AFI) zeotypes with 12-membered ring (MR) pore openings were synthesized, and denoted as CAN-[Zn(Im)] and AFI-[Zn(Im)], respectively. These two materials are the first known examples of Zn(Im) polymorphs with 12-MR pores and AFI-[Zn(Im)] has the largest pore apertures reported to date for ZIF materials. The concept that the bulky amides used were not simply acting as the solvent, but were in fact acting as SDAs or templates during the synthesis of the large pore ZIFs, was suggested by the closeness of the geometrical fit between the guest DBF and the can cages (composite building units) of the CAN-[Zn(Im)].

In recent years, domestic and international researchers have been committed to the research of lithium-ion batteries. As the key to further improving the performance of the battery, the quality of the cathode material directly affects the performance indicators of the lithium battery; thus, the cathode material occupies the core position in the lithium-ion battery. LiFePO4 is a relatively excellent material for lithium-ion batteries, which has many advantages of low cost, high capacity, and environmental friendliness. However, as a result of the low conductivity of lithium iron phosphate and the slow diffusion rate of lithium ion, the development of lithium iron phosphate in the power battery industry is restricted. As a power battery applied in real life, there is still a lot of research space in energy density, consistency, and low-temperature performance. After years of efforts, researchers continue to explore the charging and discharging principle of lithium iron phosphate, to optimize the synthesis route, and to try coating, doping modification, and other methods to improve the performance of the material. This paper analyzes and summarizes the defects of lithium iron phosphate cathode materials and modification methods and provides an outlook on the future research direction of lithium iron phosphate.

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