Adsorption-based separation is an important technology for C 2 H 2 purification due to the environmentally friendly and energy-efficient advantage. In addition to the high selectivity of C 2 H 2 /CO 2 , the high uptake of C 2 H 2 also plays an important role in the separation progress. However, the trade-off between adsorption capacity and separation performance is still in a dilemma. Herein, we report a series of cage-like porous materials named FJI-H8-R (R = Me, Et, n Pr and i Pr) which all have high C 2 H 2 uptakes at 1.01 bar and 298 K. Dynamic breakthrough studies show that they all exhibit excellent C 2 H 2 /CO 2 separation performance. Particularly, FJI-H8-Me possesses a long breakthrough time up to 90 min g -1 . Additionally, Grand Canonical Monte Carlo (GCMC) simulation reveals that the suitable pore space and geometry contribute much to the excellent separation performance.