Solvent-dependent selective cation exchange in anionic frameworks based on cobalt(ii) and triphenylamine linkers: reactor-dependent synthesis and sorption properties

Abstract

Two cobalt(ii) coordination polymers with anionic networks of formulae {(MeNH)[CoCl(ntb)]} (JUMP-2) and {(MeNH)[Co(ntb)(HO)(MeNH)]} (previously reported as MIL-144 by Livage et al., Microporous Mesoporous Mater., 2012, 157, 37) have been obtained via a solvothermal reaction of cobalt chloride and 4,4',4''-nitrilotribenzoic acid (Hntb) in DMF employing two differently-sized reactors, while using the same absolute amount of reactants. Structure analysis revealed that JUMP-2 crystallized in the monoclinic space group P2/n and displays a two-dimensional (2D) network, which by topological analysis was characterized as a layered 3-connected hcb net. The topological analysis of MIL-144 revealed a 3,6-connected net with 3,6T80 topology. The magnetic properties of JUMP-2 are indicative of independent single-ion behavior of the tetrahedral cobalt(ii) ions and showed an out-of-phase signal in the alternating-current (ac) magnetic susceptibility below 2.5 K, whereas for MIL-144 an overall antiferromagnetic interaction within the di- and trinuclear secondary building units is observed and no indication for slow magnetization dynamics. The organic cations in both frameworks could successfully be exchanged with inorganic cations under retention of the respective network structure. In the process of exchange, both compounds displayed cation selectivity based on which solvent was utilized for immersing the solids. JUMP-2 shows a preference for europium(iii) ions in DMF, whereas MIL-144 preferentially takes up lithium ions when ethanol is used. The N adsorption isotherms were measured before and after exchange and revealed a considerable improvement in the sorption properties of the exchanged samples.

Modulator Induced Formation of a Neutral Framework Based on Trinuclear Cobalt(II) Clusters and Nitrilotribenzoic Acid: Synthesis, Magnetism, and Sorption Properties

“…[43][44] This was likewise found to be the case for the previously reported anionic frameworks MIL-144 and JUMP-2. [39][40] In an attempt to synthesize a mixed ligand MOF with H 3 ntb as redox-active linker isophthalic acid was employed. However, repeated experiments consistently resulted in the formation of a polymeric material with neutral framework which was characterized to possess the formula [Co 9 (ntb) 6 (solv) 12 ] n (JUMP-3), where the coordinating solvent molecules include water, dmf, and dimethylamine (see below and Experimental Section for details).…”

“…To ascertain the role of isophthalic acid as modulator, the synthesis was repeated at the same temperature (130°C) but in the absence of the isophthalic acid. This attempt led to the formation of the anionic framework MIL-144, [39][40] thus suggesting that the modulator does trigger the formation of JUMP-3. The role of the modulator is further demonstrated by an additional experiment with deliberately added dimethylammonium chloride to the reaction mixture, that also contains the modulator isophthalic acid, which leads to the formation of the anionic framework MIL-144.…”

“…Interestingly, this values are considerably larger than those observed for the anionic framework MIL-144, but in a similar range as the values observed for the MIL-144 framework with the dimethylammonium cations exchanged by lithium ions in ethanol solution. [40] With respect to the void calculated from the crystal structure of JUMP-3 scd (0.45 cm 3 g À 1 ), the total pore volume corresponds to 49 %.…”

“…[29,31] In this report, we describe the synthesis of the neutral MOF with the formula [Co 9 (ntb) 6 (solv) 12 ] n (JUMP-3) composed of linear trinuclear cobalt(II) clusters as metal nodes coordinatively saturated by solvent molecules and nitrilotribenzoic acid linkers utilizing isophthalic acid as structure directing agent. The neutral framework of JUMP-3 represents a new type of architecture for the given combination, for which as yet only (MIL-144) [39][40] and {(Me 2 NH 2 ) 2 [CoCl(ntb)]} n (JUMP-2). [40] Herein, we will also report on the investigations into the porosity and magnetic properties of the new compound.…”

“…The neutral framework of JUMP-3 represents a new type of architecture for the given combination, for which as yet only (MIL-144) [39][40] and {(Me 2 NH 2 ) 2 [CoCl(ntb)]} n (JUMP-2). [40] Herein, we will also report on the investigations into the porosity and magnetic properties of the new compound.…”