The authors thank the Royal Society of Edinburgh and the Scottish Government for a fellowship to Dr Stephen A. Moggach, and the Leverhulme Trust for financial support.A novel method for CO2 delivery to a porous material is reported, wherein a perfluorocarbon containing dissolved CO2 has been used as a pressure-transmitting liquid in a high-pressure single-crystal X-ray diffraction experiment. Pressure causes the gas to be squeezed out of the liquid into the host crystal, monitored via a single-crystal to single-crystal phase transition on uptake of CO2.PostprintPeer reviewe