Integrating Biocatalysts into Metal-Organic Frameworks: Disentangling the Roles of Affinity, Molecular Weight, and Size

The integration of biocatalysts within metal-organic frameworks (MOFs) is attracting growing interest due to its potential to both enhance biocatalyst stability and sustain biocatalyst activity in organic solvents. However, the factors that facilitate the post-synthetic infiltration of such large molecules into MOF pores remain unclear. This systematic study enabled the identification of the influence of biocatalyst molecular size, molecular weight and affinity on the uptake by an archetypal MOF, NU-1000. We analyzed a range of six biocatalysts with molecular weights from 1.9 kDa to 44.4 kDa, respectively. By employing a combination of fluorescence tagging and 3D-STED confocal laser scanning microscopy, we distinguished between biocatalysts that were internalized within the MOF pores and those sterically excluded. The catalytic functions of the biocatalysts hosted within the MOF were investigated and found to show strong variations relative to the solvated case, ranging from a two-fold increase to a strong decrease.