a b s t r a c t Sorbent hollow fibres, generally prepared by fully encapsulating an adsorbent within a polymer binder such as polyethersulfone (PES), provide a low pressure drop alternative to conventional packed beds. These fibres have a high external surface area to volume ratio, enabling smaller bed sizes, and a highly porous structure resulting in low mass transfer resistance while maximising sorption efficiency. How-ever, adsorbent hollow fibres prepared with PES suffer from loss of some adsorption capacity due to the polymer binder. This paper describes a novel formulation of composite hollow fibres containing acti-vated carbon and PIM-1, a polymer of intrinsic microporosity, as an active binder designed to enhance the total adsorption capacity. Octane has been selected as a model hydrocarbon, and nitrogen and octane iso-therms are reported for both PES and PIM-1 based hollow fibres, each containing the same activated car-bon. Theoretical BET surface areas were calculated for each type of fibre based on a weighted average of the surface areas of its individual components (i.e. polymer and carbon). The measured surface area of the PIM-1 fibres was remarkably consistent with the theoretical value, while the measured surface area and octane uptake for PES fibres were $10% lower than the theoretical values, indicating some blockage of the adsorbent by the polymer matrix. PIM-1 adsorbent fibres were found to fully utilise the capacity of the supported carbon, as well as providing additional sites for adsorption on the polymer, resulting in a max-imum octane uptake of 50% w/w – approximately twice that of the PES-based fibres.