CO2 confinement by a novel molecular spring architecture via reactive molecular dynamics

Abstract In this study, we propose a novel framework with a hybrid molecular spring architecture based on a spiral/helical-type nanostructure supported by slab layers and bridged by organic linkers. Hierarchically, the framework consists of symmetrical nickel (Ni)-doped α-Al 2 O 3 slabs, a sulfur-rich helical cage, and multifunctional 2,5-dimercaptoterephthalic acid (DMBDC) organic linkers. Ni/α-Al 2 O 3 supported, DMBDC bridged and helical pillared framework (SL-HPF) contributed to dynamic structural stability, the synergistic role of interfacial coupling and molecular confinement through reactive force field (ReaxFF) molecular dynamics (MD) simulations. The CO 2 confinement performance of SL-HPF was analysed by atomic arrangements via MD trajectories, self-diffusion coefficient (D), radial distribution functions (RDF), gas viscosity measurements. To isolate the contribution of the helical cage, a control system was conducted on pure Ni/α-Al 2 O 3 slabs. The D and gas viscosity of CO 2 for only control system are 1.451 × 10 –7 m 2 s −1 and 0.0163 Js m −3 , respectively. In contrast, the SL-HPF exhibited an enhanced molecular trapping because CO 2 molecules systematically penetrated the helical cage due to strong confinement effects. For SL-HPF, D and local fluid viscosity of CO 2 were calculated as 1.812 × 10 –8 m 2 s −1 and 0.0347 Js m −3 , respectively. Structural localization was further validated by a highly dense S-C pair RDF correlation peak at 1.8 Å within the helical cage. These results demonstrate that the synergy between catalytic metal sites, elastic organic springs, and high-affinity sulfur vacancies in the helical cage can successfully immobilize gas molecules through molecular trapping rather than chemical bond disruption. This work presents a novel molecular spring design and hybrid framework for next-generation environmental remediation technologies.