Hollow zeolite microspheres as a nest for enzymes: a new route to hybrid heterogeneous catalysts for chemo-enzymatic cascade reactions

Integrating enzymatic and heterogeneous catalysis can pave the way to new and performing cascade chemical processes. In this perspective, the preparation of bifunctional structures combining both an active inorganic catalyst and an enzyme is a key. However, such combinations are not straightforward, for example in the case of zeolite catalysts for which enzyme immobilization would be restricted to the external surface. We overcame this challenge by developing a new kind of hybrid catalysts based on hollow zeolite microspheres. The method leverages on the aerosol-assisted assembly of TS-1 nanocrystals to form hollow zeolite microspheres with tailored hierarchical texture and high epoxidation activity in water. The latter spheres were subsequently loaded with glucose oxidase enzymes which were then cross-linked to secure their entrapment. This controlled design allows to combine all the decisive features of the zeolite with a high enzyme loading. A chemo-enzymatic reaction is demonstrated, where the structured zeolite microsphere is used both as a nest for the enzyme and as an efficient inorganic heterogeneous catalyst. The enzyme ensures the in situ production of H₂O₂ subsequently utilized by the zeolite for the epoxidation of allylic alcohol. We anticipate our method will open up new perspectives in the field of hybrid catalysis. Starting from various catalytic nano-building blocks, hollow microspheres with open entry ways could be prepared using the aerosol process and could be used as vessels for enzymes or even multi-enzymatic systems, thereby giving access to a multitude of new heterogeneous chemo-biocatalysts.