Carbon dioxide (CO2) separation is central to technologies ranging from natural gas purification to hydrogen production and carbon management. One widely used approach relies on thin filtering materials called membranes. However, these membranes face a major challenge: materials that allow CO2 to pass through quickly are often less effective at separating it from other gases, while highly selective materials usually slow the flow of CO2. This balancing act is known as the permeability-selectivity trade-off.