To provide a new compound with pores finely tunable in size so as to take up a specific element and release the specific element taken up in the pores as necessary, a synthesis method of the new compound, and a separation and recovery agent. The new compound represented by the following molecular formula:

(NH.sub.4)[Ln(C.sub.2O.sub.4).sub.2(H.sub.2O)]

wherein Ln represents a lanthanide selected from Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

To provide a new compound with pores finely tunable in size so as to take up a specific element and release the specific element taken up in the pores as necessary, a synthesis method of the new compound, and a separation and recovery agent. The new compound represented by the following molecular formula:

(NH.sub.4)[Ln(C.sub.2O.sub.4).sub.2(H.sub.2O)]

wherein Ln represents a lanthanide selected from Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

The present invention related to the use of compounds of general formula (I) for separations of rare earth elements (lanthanides) by precipitation, wherein R is selected from the group consisting of H; —CH2COOH; R.sup.2, R.sup.3, R.sup.4, R.sup.5 and R.sup.6 areindependently selected from the group consisting of H; OH; —NO2; —COOH; phenyl; and/or R.sup.2 and R.sup.3 or R.sup.3 and R.sup.4 or R.sup.4 and R.sup.5 or R.sup.5 and R.sup.6 The invention further relates to a method of separation of rare earth elements by precipitation. together with two neighbouring carbon atoms of the aromatic ring form a six-membered aromatic ring.

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Provided is a nanoparticle including: a core structure; and a shell structure covering the core structure and separated from the core structure by a nanogap, wherein a macrocyclic host molecule exhibiting hydrophobicity inside and hydrophilicity outside and a Raman-active material inserted into the macrocyclic host molecule are provided on a surface of the core structure, and the macrocyclic host molecule and the Raman-active material fill the nanogap.

Provided is a nanoparticle including: a core structure; and a shell structure covering the core structure and separated from the core structure by a nanogap, wherein a macrocyclic host molecule exhibiting hydrophobicity inside and hydrophilicity outside and a Raman-active material inserted into the macrocyclic host molecule are provided on a surface of the core structure, and the macrocyclic host molecule and the Raman-active material fill the nanogap.

To provide a new compound with pores finely tunable in size so as to take up a specific element and release the specific element taken up in the pores as necessary, a synthesis method of the new compound, and a separation and recovery agent. The new compound represented by the following molecular formula:
(NH.sub.4)[Ln(C.sub.2O.sub.4).sub.2(H.sub.2O)]
wherein Ln represents a lanthanide selected from Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

To provide a new compound with pores finely tunable in size so as to take up a specific element and release the specific element taken up in the pores as necessary, a synthesis method of the new compound, and a separation and recovery agent. The new compound represented by the following molecular formula:
(NH.sub.4)[Ln(C.sub.2O.sub.4).sub.2(H.sub.2O)]
wherein Ln represents a lanthanide selected from Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

A method for extracting a rare earth metal from a mixture of one or more rare earth metals, said method comprising contacting an acidic solution of the rare earth metal with a composition which comprises an ionic liquid to form an aqueous phase and a non-aqueous phase into which the rare earth metal has been selectively extracted, wherein the ionic liquid has the formula [Ca.sup.++][X′], where [X′] represents a phosphinate anion.

A method for extracting a rare earth metal from a mixture of one or more rare earth metals, said method comprising contacting an acidic solution of the rare earth metal with a composition which comprises an ionic liquid to form an aqueous phase and a non-aqueous phase into which the rare earth metal has been selectively extracted, wherein the ionic liquid has the formula [Ca.sup.++][X′], where [X′] represents a phosphinate anion.

A production method for producing a halide includes a heat-treatment step of heat-treating, in an inert gas atmosphere, a mixed material in which LiX and YZ.sub.3 are mixed, where X is an element selected from the group consisting of Cl, Br, and I, and Z is an element selected from the group consisting of Cl, Br, and I. In the heat-treatment step, the mixed material is heat-treated at higher than or equal to 200° C. and lower than or equal to 650° C.