Regulating Ga(III) Capture and Selectivity by O–Donor Coordination Environments in Functionalized Conjugated Microporous Polymers

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Selective enrichment of Ga(III) from acidic zinc hydrometallurgical solutions remains challenging because of the low Ga(III) concentration and the coexistence of competing metal ions. Herein, an ester-containing conjugated microporous polymer, CMP-mCOOCH3, was used as a precursor to construct hydroxamic acid-functionalized CMP-mCONHOH and carboxyl-functionalized CMP-mCOOH through postsynthetic modification. This design enables a direct comparison of how different O-donor coordination environments regulate Ga(III) adsorption within a similar porous framework. Both materials showed efficient Ga(III) uptake at pH 3 and 298 K, with adsorption capacities of 174.75 mg g-1 for CMP-mCONHOH and 249.47 mg g-1 for CMP-mCOOH. The adsorption processes followed pseudo-second-order kinetics and Langmuir isotherm behavior, indicating coordination-driven monolayer adsorption. In competitive systems, both adsorbents maintained good Ga(III) uptake in the presence of Al(III), Zn(II), and Cu(II), whereas In(III) showed stronger competition. CMP-mCOOH exhibited a higher adsorption capacity, while CMP-mCONHOH showed stronger chelation-driven recognition, especially for Ga/In separation. After five adsorption-desorption cycles, CMP-mCONHOH and CMP-mCOOH retained 90.4% and 92.2% of their adsorption efficiencies, respectively. Spectroscopic analyses and theoretical calculations revealed that Ga(III) binding mainly occurred through oxygen-donor coordination. These results provide guidance for designing regenerable porous polymer adsorbents for gallium recovery from acidic metallurgical systems.

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