Limestone can be used to generate a sorbent suitable for CO2 capture via the reversible carbonation of CaO, in a process often referred to as calcium looping. This sorbent loses reactivity to CO2 upon cycles of carbonation and calcination (the reverse of carbonation). Several methods of improving sorbent performance have previously been investigated, including by generating synthetic sorbents or simple doping. Here, we demonstrate, for the first time, that sorbent performance can be enhanced by simple doping with seawater. This effect is consistent across five different limestones investigated and can be enhanced by steam addition. This would be a simple and inexpensive method for improving sorbent performance in calcium looping processes. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd.