Shaping and silane coating of a diamine-grafted metal-organic framework for improved CO₂ 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.