A Cationic
Metal–Organic Solid Solution Based
on Co(II) and Zn(II) for Chromate Trapping
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Abstract
We report the synthesis and characterization
of a solid solution
series of cationic metal–organic materials with full compositional
range from pure Co(II) to Zn(II) end-members. The materials consist
of [Zn<sub><i>x</i></sub>Co<sub>1–<i>x</i></sub>(H<sub>2</sub>O)<sub>4</sub>(4,4′-bipy)<sub>2</sub>]<sup>2+</sup> metal–organic clusters that π–π
stack into 2-D positively charged layers, with the metal ratio tunable
by molar ratio under hydrothermal conditions. The interlamellar α,ω-alkanedisulfonate
serves as an anionic template and noncovalently interacts with the
cationic layers. The weak interaction allows anion exchange for toxic
oxometal anions, such as chromate, CrO<sub>4</sub><sup>2–</sup>. The highest chromate adsorption capacity was 68.5 mg/g (0.43 mol/mol)
for the as-synthesized 50 mol % Co(II)-incorporated material. Our
cationic material can also selectively trap these toxic oxo-anions
when nontoxic anions (e.g., nitrate, sulfate) were present in an over
50-fold excess concentration