Monolith-Supported Amine-Functionalized Mg₂(dobpdc) Adsorbents for CO₂ Capture

The potential of using an amine-functionalized metal organic framework (MOF), mmen-M₂(dobpdc) (M = Mg and Mn), supported on a structured monolith contactor for CO₂ capture from simulated flue gas is explored. The stability of the unsupported MOF powders under humid conditions is explored using nitrogen physisorption and X-ray diffraction analysis before and after exposure to humidity. Based on its superior stability to humidity, mmen-Mg₂(dobpdc) is selected for further growth on a honeycomb cordierite monolith that is wash-coated with α-alumina. A simple approach for the synthesis of an Mg₂(dobpdc) MOF film using MgO nanoparticles as the metal precursor is used. Rapid drying of MgO on the monolith surface followed by a hydrothermal treatment is demonstrated to allow for the synthesis of a MOF film with good crystallite density and favorable orientation of the MOF crystals. The CO₂ adsorption behavior of the monolith-supported mmen-Mg₂(dobpdc) material is assessed using 10% CO₂ in helium and 100% CO₂, demonstrating a CO₂ uptake of 2.37 and 2.88 mmol/g, respectively. Excellent cyclic adsorption/desorption performance over multiple cycles is also observed. This is one of the first examples of the deployment of an advanced MOF adsorbent in a scalable, low-pressure drop gas-solid contactor. Such demonstrations are critical to the practical application of MOF materials in adsorptive gas separations, as structured contactors have many practical advantages over packed or fluidized beds.