As a unique polymer of intrinsic microporosity, PIM-1 has great potential in mixed matrix membranes (MMMs) for gas separation with ultra-high permeability. However, the separation performance, e.g. CO₂/N₂ separation, is still limited by its poor selectivity. In this work, PIM-1-based MMMs containing tartaric acid anion intercalated layered double hydroxides (TA-LDH) nanofillers are successfully prepared. The uniformly dispersed TA-LDH in the PIM-1 matrix contributes to optimizing the stacking of polymer chains for accessible pores, which is conducive to CO₂ diffusion. In addition, the assistant experiment and theoretical calculation point out that the -COO-, –OH between the TA-LDH layers had an affinity for CO₂, creating a two-dimensional fast transport channel between the enlarged interlayer space. Compared with the pristine PIM-1 membrane, the CO₂ permeability and CO₂/N₂ selectivity of 0.7 % TA-LDH/PIM-1 membrane is increased by 43.19 % and 105.48 %. The excellent gas separation performance with CO₂ permeability of 8343.18 Barrer and CO₂/N₂ selectivity of 39.02 exceeds the 2019 Robson upper limit. This paves a new way to improve the gas separation performance of PIM-1-based MMMs and suggests high perspectives for real applications.