We herein report an optimal modulated hydrothermal (MHT) synthesis of a highly stable zirconium metal-organic framework (MOF) with an optimum aperture size of 3.93 A degrees that is favorable for CO2 adsorption. It exhibits excellent CO2 uptake capacities of 2.50 and 5.63 mmol g(-1) under 0.15 and 1 bar at 298 K, respectively, which are among the highest of all the pristine water-stable MOFs reported so far. In addition, we have designed a lab-scale breakthrough set-up to study its CO2 capture performance under both dry and wet conditions. The velocity at the exit of breakthrough column for mass balance accuracy is carefully measured using argon with a fixed flow rate as the internal reference. Other factors that may affect the breakthrough dynamics, such as pressure drop and its impact on the roll-up of the weaker component have been studied in details. (C) 2017 American Institute of Chemical Engineers AIChE