This work describes the development of an optimized spin dope for the production of open-porous, mechanically stable fiber sorbents. The fiber sorbents in this work consist of Torlon((R)) polymer matrix with dispersed zeolite particles to act as the sorbent sites. Initial spinning attempts with dopes consisting of Torlon((R)), 13X, n-methylpyrrolidone (NMP) and water yielded fibers that were prone to breaks during production and had a large number of macrovoids. To remedy this, polyvinylpyrrolidone (PVP) was introduced in the dope as a pore former and macrovoid suppressant. A separate phase diagram was developed to accommodate PVP and a new preferred spin dope composition was identified. Fibers were spun based on this concentration with adequate spinning behavior. Microscopy analysis showed that PVP was successful in reducing the prevalence of macrovoids in the fiber cross section. High sorbent wall permeance was also retained with the PVP. Further analysis of permeance measurements revealed that Knudsen flow was dominant over Poiseuille flow. The estimated pore sizes implying that the transport process lies in the transition region between molecular and Knudsen diffusion. POLYM. ENG. SCI., 58:2106-2114, 2018. (c) 2018 Society of Plastics Engineers