Selective Crystallization of Rare‐Earth Ions into Cationic Metal‐Organic Frameworks for Rare‐Earth Separation

Abstract

For rare-earth separation, selective crystallization into metal-organic frameworks (MOFs) offers new opportunities. Especially important is the development of MOF platforms with high selectivity toward target ions. Here we report a MOF platform (CPM-66) with low-coordinationnumber environment for rare-earth ions. This platform is highly responsive to the size variation of rare-earth ions and shows exceptional ion-size selectivity during crystallization. CPM-66 family are based on M 3 O trimers (M = 6-coordinated Sc, In, Er-Lu) that are rare for lanthanides. We show that the size matching between urea-type solvents and metal ions is crucial for their successful synthesis. We further show that CPM-66 enables a dramatic multi-fold increase in separation efficiency over CPM-29 with 7-coordinated ions. This work provides some insights into methods to prepare low-coordinate MOFs from large ions and such MOFs could serve as highefficiency platforms for lanthanide separation, as well as other applications.

Sc(iii)-Based metal–organic frameworks

“…47 In 2016, Sa ´nchez et al 48 reported similar results for NOTT-401, where the capacity improved from 1.2 wt% (under dry conditions) to 3.9 wt% under 5% RH at 30 1C. 49 Colour code: C, gray; O, red; Sc, purple; S, yellow; N, green; H, white.…”

“…One of the two kinds of pores identified in the MOF is filled with pendant urea solvents and nitrate ions. The compound exhibits a BET area of 172.7 m 2 g À1 and high thermal stability up to 300 1C 49. {[Sc(l-pmdc)(l-ox) 0.5 (H 2 O) 2 ]Á3H 2 O} n , {[Sc(l-pmdc)(l-OH) (H 2 O)]ÁH 2 O} n , {(NH 4 )[Sc(l-ox) 2 ]Á2H 2 O} n , {(tma) 2 [ScK(l-form) 6 ]} n , and [Sc 2 (pmdc)(OH) 3 Cl]ÁDMFÁ2H 2 O. Cepeda et al (2015) 50 studied the factors governing the hydro-and solvothermal reactions of ScCl 3 with pyrimidine-4,6-dicarboxylic acid (H 2 pmdc) (Scheme 1), which afforded {[Sc(m-pmdc)(m-ox) 0.5 (H 2 O) 2 ]Á3H 2 O} n (10), {[Sc(m-pmdc) (m-OH)(H 2 O)]ÁH 2 O} n (11), {(NH 4 )[Sc(m-ox) 2 ]Á2H 2 O} n (12), {(tma) 2 [ScK(mform) 6 ]} n (13), and [Sc 2 (pmdc)(OH) 3 Cl]ÁDMFÁ2H 2 O (14) (ox = oxalate, tma = tetramethylammonium, form = formate) (Fig.…”

“…Fig.15SBU of NOTT-401 (a)10 and CPM-66A-Sc (b) 49. Colour code: C, gray; O, red; Sc, purple; S, yellow; N, green; H, white.…”

A Metal‐Organic Framework (MOF)‐Based Multifunctional Cargo Vehicle for Reactive‐Gas Delivery and Catalysis

“…Due to their toxicity and reactivity, expensive safety measures are required to handle, store, and transport these gases safely, thereby placing their usage in synthetic chemistry under strict regulations [7] . Herein, we probed metal‐organic frameworks (MOFs), [8–33] specifically their reversible gas adsorption and catalytic activity, to carry out chemical reactions in organic solvents. Thus, we explored the dual role of MOFs as a catalyst and carrier of reagents on the example of reactive gases.…”

Selective Crystallization of Rare‐Earth Ions into Cationic Metal‐Organic Frameworks for Rare‐Earth Separation

“…Figure2. Structures of CPM-66 [17]. a) the formation of trimer building blocks in CPM-66A and CPM-66B; b) acs topology of CPM-66; c) the framework of CPM-66B viewed along c direction; d) rare-earth ions with their corresponding ionic radii (unit: pm) at coordination number of 6 (In 3+ is also included).…”