Cyclic adsorption of water vapour on CuBTC MOF: Sustaining the hydrothermal stability under non-equilibrium conditions

Metal organic frameworks (MOFs) based adsorption processes for gas separation from humid streams are limited by the hydrothermal stability of MOFs. This work presents a comprehensive study of the hydrothermal stability of CuBTC (BTC = benzene-1,3,5-tricarboxylate) MOF when exposed to humid streams in cyclic operations. We show that water uptake is slow, and that adsorption processes will most likely operate under non-equilibrium conditions. CuBTC does not show signs of decomposition when exposed to low water concentration and room temperature (up to water partial pressures of 6 mbar and 25 °C) for up to 48 h of cyclic operation. Nevertheless, short cycles (of less than 15 min per pressure stage) are required when exposed to high water vapour content (up to 70 mbar, 50 °C). This work demonstrates the need of tailoring the length of water exposure to avoid the equilibrium adsorption of water vapour on CuBTC and maintain the adsorbent integrity.