Research Papers
Latest publications from our group
Metal–organic frameworks (MOFs) with ultra-small pores offer an optimal environment to effectively capture guest molecules such as CO2. Subtle local dynamics of their frameworks, either throughout reorientation of functional groups grafted to the organic linkers or those present in their inorganic nodes, is expected to play a major role in their sorption behaviours. Herein, we investigated the local dynamics of bridging hydroxyl group (μ2-OH) in the ultra-small pore MOF MIL-120(Al) using DFT combined with a purpose-trained machine-learning potential (MLP). Six distinct μ2-OH configurations were identified with low interconversion barriers (0.07–0.19 eV), indicating significant dynamic behaviour at room temperature. Grand canonical Monte Carlo and hybrid GCMC–MD simulations driven by the MLP demonstrate that adsorption isotherms and low-pressure behaviour are sensitive to μ2-OH ordering and whether framework and cell relaxation are considered. While standard rigid force-field simulations overestimated the heat of adsorption, MLP-driven GCMC-MD simulations successfully captured framework relaxation and dynamic μ2-OH reorientation under CO2 loading. This work establishes that a reliable description of the local structure, such as reorientation/flipping of bridging hydroxyl groups, is a key feature to gain an accurate description of the guest locations and energetics in ultra-small pore MOFs.
Water scarcity remains one of the most pressing global challenges, driving the urgent need for next-generation desalination technologies that can overcome the long-standing trade-off between water permeability and ion selectivity. Here, we introduce a molecular design blueprint based on a two-dimensional metal−organic framework (2D-MOF) monolayer, NiF2(pyz)2, featuring intrinsically aligned ∼4 Å pores and high structural regularity. Using systematic all-atom molecular dynamics simulations, we demonstrate that this monolayer achieves ultrahigh water permeability while maintaining 100% Na+/Cl− rejection across a wide range of applied pressures. We attribute this exceptional performance to a synergistic combination of low interfacial water density, reduced free energy barriers for water transport, and a high pore area-to-surface area ratio, captured by a proposed dimensionless descriptor. Compared to conventional 2D membranes with artificial nanopores, which often suffer from fabrication complexity, pore size variability, and mechanical fragility, the NiF2(pyz)2 monolayer offers a robust alternative with precisely defined nanochannels combined with mechanical and hydrothermal stability. This work pushes the boundaries of the structure−function paradigm in membrane science by establishing that atomically engineered intrinsic porosity, rather than postfabricated artificial channels, is the key to achieving fast and selective water transport. Our findings lay the groundwork for the rational design of high-efficiency desalination membranes and suggest possible approaches for using MOFs in sustainable water purification technologies.
Synthesizing polynitrogen compounds that remain stable at ambient conditions is particularly challenging because species beyond the N ≡ N triple bond are inherently unstable. In this study, we combine first-principles calculations with a machine-learning potential (MLP) to investigate the ambient stability of planar cyclo-N4 units embedded in a two-dimensional t-FeN4 monolayer. Our results show that strong Fe–N coordination inhibits N ≡ N reformation, enabling the square cyclo-N4 motif to remain dynamically stable and covalently bonded without high-pressure synthesis. Furthermore, this structure exhibits tunable magnetic anisotropy and a Néel temperature above 600 K, indicating potential for room-temperature spintronic applications. The MLP also enables the simulation of systems comprising over 100,000 atoms, including periodic sheets, nanoribbons, nanomatrices and nanosheets, revealing their structural integrity under thermal fluctuations. These results demonstrate that two-dimensional confinement provides a promising route to stabilize exotic nitrogen topologies, linking quantum-mechanical accuracy with mesoscale modelling for future spin-based technologies.
