Polyimide Covalent–Organic Frameworks for Aqueous Actinide Sequestration: Combined Ab Initio and Molecular Dynamics Studies

The sustainable expansion of nuclear power hinges on
the effective
management of actinide-containing waste streams, particularly through
the capture and recovery of plutonium and uranium. Selective sequestration
of these actinides is crucial not only for environmental remediation
but also for recycling these finite and nonrenewable resources in
advanced nuclear fuel cycles. Covalent-organic frameworks (COFs) have
emerged as next-generation sorbents, offering versatile structural
designs, exceptional surface areas, and precisely tunable binding
sites to enable highly selective sorption and efficient regeneration.
In this in silico study, we evaluate a series of polyimide COFs (PI-COFs)
for their ability to detect and capture radioactive actinides, UO22+ and Pu4+, from aqueous solutions.
We employ a multiscale computational approach that combines ab initio
density functional theory (DFT) calculations with molecular dynamics
(MD) simulations to characterize the energetics and diffusion dynamics
of adsorbates within adsorbent frameworks. Our results show that PI-COF-1
displays the strongest adsorption for UO22+,
while PI-COF-3 exhibits the highest adsorption energy for Pu4+ and correspondingly strong selectivity. The combined adsorption
and diffusion trends reveal how the stacking arrangement and nitrogen-rich
functional groups strengthen host–guest interactions and modulate
ion transport. These insights identify specific PI COF structural
features that promote efficient actinide sequestration and provide
guidance for targeted experimental validation and material optimization.