Multiscale kinetic model of ethylene oligomerization in Ni-NU-1000 metal-organic framework

Single-atom catalysts (SACs) provide isolated, well-defined metal sites that are suited for mechanistic modeling in porous materials such as metal-organic frameworks (MOFs). However, the influence of framework topology and mass transport on catalytic outcomes remains poorly understood. Here we develop a multiscale kinetic model for ethylene oligomerization in Ni-grafted NU-1000 that combines density functional theory (DFT)-derived free-energy barriers with adsorption and diffusion descriptors. The framework predicts product distributions under realistic reaction conditions. The simulations show that flow-mode operation favors selective C4 H 8 formation across a temperature range. This selectivity window progressively narrows with increasing effective diffusion length and catalytic-site density, as longer residence times enhance chain growth beyond dimerization. In contrast, batchmode operation shifts the product distribution toward heavier olefins. These trends provide practical guidance for tuning operating conditions and material properties to achieve desired selective Ni-MOF
catalysts.