Electron-correlation driven structural instability and adsorption mechanism in the metal–organic framework NU2100

Abstract

Metal–organic frameworks have garnered considerable interest due to their high porosity, large surface areas, and often easy synthesis, offering a vast structural diversity of interest to wide-ranging applications. Recently, the novel structure NU2100 showed notable selectivity of CO₂ and H₂ compared to C₂H₄ and C₂H₆, a promising step towards integrated carbon capture and utilization. Here, we investigate NU2100 using ab initio techniques to understand the mechanism of adsorption observed experimentally. Our calculations uncover a surprising structural instability—associated with the strongly correlated Cu(I) sites—that drives a gate-opening effect. This structural instability has significant implications for the binding affinity and diffusion barriers of the guest molecules in NU2100. The thermodynamic, kinetic, and structural stability insights provided by our calculations lead to a complete mechanistic understanding of the adsorption behavior in NU2100 observed experimentally.