Efficient CO2 separation in mixed matrix membranes with a hierarchical pore carbon nanostructure

Mixed matrix membranes (MMMs) based on Pebax MH 1657 (Pebax) and “sea‐urchin” like hierarchical mesopore–micropore carbon nanotube nanopolyhedras (CNPs) are fabricated for CO 2 separation. The membranes have an efficient improvement in CO 2 permeability and CO 2 /CH 4 selectivity with the addition of CNPs. The improved gas‐separation performance was attributed to the hierarchical mesopore–micropore structure of nanopolyhedras in CNPs and the “sea‐urchin” like structure of CNPs. First, abundant mesopores (4.8 nm) with a large pore volume and a connected porous network structure in nanopolyhedras can provide convenient gas transmission pathways to improve the CO 2 permeability. Second, micropores (1.1 nm) in nanopolyhedras play a role of molecular sieves and the outstretched CNTs of the “sea‐urchin” like structure of CNPs can extend the gas‐delivery path, which will enhance the CO 2 /CH 4 selectivity. Therefore, the CO 2 permeability and CO 2 /CH 4 selectivity are significantly enhanced. The MMMs with 8 wt% CNP show the highest CO 2 permeability of 510.1 Barrer and CO 2 /CH 4 selectivity of 56.8, the CO 2 separation performance surpassed the 2008 Robeson upper bound line.