Porphyrin-based MOF/graphene composites for selective capture of yttrium: adsorption property and study of mechanism

This study prepared a porous porphyrin-based metal organic frameworks/ reduced graphene oxide ((Fe-P)n-MOF/graphene) composite via a hydrothermal reduction method using tetracarboxyphenyl porphyrin (TCPP) and FeCl3 as the main raw materials, which served as a selective adsorbent for yttrium ions (Y3+). The adsorption performance of the composite toward Y3+ was investigated, and the results indicated a maximum adsorption capacity of 102.1 mg/g. The adsorption process followed the quasi-second-order kinetic model and the Langmuir isotherm model, indicating a monolayer chemical adsorption mechanism. The composite material was comprehensively characterized to analyze its adsorption mechanism. Combined with density functional theory (DFT) calculations, the electrostatic potential distribution of (Fe-P)n-MOF and the binding energy of adsorption sites toward metal ions were simulated to further elucidate the Y3+ adsorption mechanism. In practical rare-earth leaching solutions, the composite exhibited excellent selective adsorption capability for Y3+, and after more than five regeneration cycles, the recovery rate remained above 90%. These results demonstrate that (Fe-P)n-MOF/graphene can be used as a promising adsorbent for Y3+.