Fig. 3: Adsorption behaviors of ZIOS and ZIF-8.

a, b Copper (II) ion adsorption kinetics collected on ZIF-8 and ZIOS (error bars were obtained from three different adsorption tests conducted on materials synthesized from random batches). c Experimental copper adsorption isotherm for ZIOS (symbols) shown with fit using single-site (blue line) and dual-site (dotted line) Langmuir models. d Plots of distribution coefficients for ZIOS versus copper ion concentration (red triangles), compared with coefficients for other state-of-the-art copper ion adsorbents: a diaminoethane-functionalized mesoporous sol-gel (black triangles, ref. ¹²), double hydroxides intercalated with polysulfides (purple diamond, ref. ³²), PAF-1-SMe (blue square, ref. ⁵), and a Ca²⁺ two-dimensional MOF (gray circle, ref. ⁷¹). e Copper selectivity of ZIOS and ZIF-8 when exposed to aqueous solutions (pH = 2.45 and 3.94) simultaneously containing equimolar concentration of Ca²⁺, Cu²⁺, Fe²⁺/Fe³⁺, Mn²⁺, Na⁺, and Ni²⁺ (present as Cl⁻ or NO₃⁻ salts). f Copper(II) adsorption data for ZIOS at low copper concentrations. Uptake of copper(II) in ZIOS at these trace levels is excellent: ~65% at 0.45 ppm Cu²⁺ and ~95% at 2.5 ppm Cu²⁺.