Severe CO₂ emissions has posed an increasingly alarming threat, motivating the development of efficient CO₂ capture materials, one of the key parts of carbon capture, utilization, and storage (CCUS). In this study, a series of metal–organic frameworks (MOFs) named Sc-X (X = S, M, L) were constructed inspired by recorded MOFs, Zn-BPZ-SA and MFU-4l-Li. The corresponding isoreticular double-interpenetrating MOFs (Sc-X-IDI) were subsequently constructed via the introduction of isoreticular double interpenetration. Grand canonical Monte Carlo (GCMC) simulations were adopted at 298 K and 0.1–1.0 bar to comprehensively evaluate the CO₂ capture and separation performances in Sc-X and Sc-X-IDI, with gas distribution, isothermal adsorption heat (Qst), and van der Waals (vdW)/Coulomb interactions. It is showed that isoreticular double interpenetration significantly improved the interactions between adsorbed gases and frameworks by precisely modulating pore sizes, particularly observed in Sc-M and Sc-M-IDI. Specifically, the Qst and Coulomb interactions exhibited a substantial increase, rising from 28.38 and 22.19 kJ mol^–1 in Sc-M to 43.52 and 38.04 kJ mol^–1 in Sc-M-IDI, respectively, at 298 K and 1.0 bar. Besides, the selectivity of CO₂ over CH₄/N₂ was enhanced from 55.36/107.28 in Sc-M to 3308.61/7021.48 in Sc-M-IDI. However, the CO₂ capture capacity is significantly influenced by the pore size. Sc-M, with a favorable pore size, exhibits the highest capture capacity of 15.86 mmol g^–1 at 298 K and 1.0 bar. This study elucidated the impact of isoreticular double interpenetration on the CO₂ capture performance in MOFs.