Molecular-level understanding of highly selective heavy rare earth element uptake by organophosphorus modified MIL-101(Cr)

Selective separation of rare earth elements (REEs) from solutions mixed heavy and light metals by solid adsorbents is an important challenge in the fields water treatment metal recovery. The main instability many adsorbents, specifically metal–organic frameworks (MOFs), their low selectivity. Grafting particular organophosphorus compounds (OPCs) on MIL-101(Cr) MOF can provide both stability When tributyl phosphate (TBP), bis(2-ethylhexyl) hydrogen (D2EHPA or HDEHP) bis(2,4,4-trimethylpentyl) phosphinic acid (Cyanex®-272) OPCs are grafted applied to mixed-metal aqueous containing Co2+, Ni2+, Cu2+, Zn2+, Nd3+, Gd3+ Er3+, offers high selectivity towards Er3+ REEs (with stronger affinity Er3+). However, underlying chemistry unknown factors leading remain poorly understood. To uncover key molecular-level factors, we performed state-of-the-art computational simulations using a combination high-level density functional theory (DFT), semi-empirical calculations, configurational sampling ion-MOF binding modes solutions. Our simulation study reproduced available experimental results, addition determining contributing intermolecular interactions, uptake most significant structural features for improving REEs. Therefore, our result rationalization mechanism REE OPC-grafted MOFs quantum mechanical electrostatic principles. results guidelines synthesis structures with enhanced stability. Moreover, efficient framework proposed facilitate comprehensive modeling similar systems.