Simultaneous macroscopic structuring and microscopic structure tuning of a metal-organic framework using alginate bead and different drying conditions

In this study, a novel method for simultaneous macroscopic structuring and microscopic structure tuning of MOFs was developed. The strategy used to accomplish these goals involves a combination of beading with alginate polymers and drying utilizing two different methods. Specifically, in the first step the representative MOF Fe‒benzene-1,3,5-tricarboxylate MOF (MIL-100(Fe)) is bead molded by alginate polymer. Subsequent drying of the beads is performed by using either heat-drying or freeze-drying. In terms of their macroscopic structure, the freeze-dried beads shrink slightly more than pre-dried beads, whereas the heat-dried beads shrink ∼70% more than pre-dried beads. The bead drying/shrinkage processes lead to formation of two different microscopic structures of MIL-100(Fe) that differ in the degree to which alginate polymer penetration into pores occurs. The degree of penetration is higher in the MIL-100(Fe) polymer composite produced by using the heat-drying protocol. It was also shown that the degree of polymer penetration governs pore size distributions and interaction energies between gases and MIL-100(Fe).