Shaping and silane coating of a diamine-grafted metal-organic framework for improved CO 2 capture

Although metal-organic framework (MOF) powders can be successfully shaped by conventional methods, postsynthetic functionalization of the shaped MOFs remains almost unexplored, yet is required to overcome intrinsic limitations, such as CO2 adsorption capacity and stability. Here, we present a scalable synthesis method for Mg2(dobpdc) MOF and its shaped beads, which are obtained by using a spray dry method after mixing Mg2(dobpdc) powders with alumina sol. The synthesized MOF/Al beads have micron-sized diameters with a moderate particle size distribution of 30–70 μm. They also maintain a high mechanical strength. N-ethylethylenediamine (een) functionalization and coating with long alkyl chain silanes results in een-MOF/Al-Si, which exhibits a significant working capacity of >11 wt% CO2 capture and high hydrophobicity. The een-MOF/Al-Si microbeads retain their crystallinity and improved CO2 uptake upon exposure to humid conditions for three days at a desorption temperature of 140 °C. Metal organic frameworks (MOFs) are promising for CO2 capture. Here, the Mg2(dobpdc) MOF is synthesized as micron-sized beads with a silane coating resulting in > 11 wt% CO2 absorption, which is retained after three days in a humid environment at 140 °C.