Interconnected gelatine/graphene oxide Pickering polyHIPE hydrogels as macromolecular scaffolds for continuous-flow...

Gelatine-based hydrogels are attractive macromolecular scaffolds for water-treatment applications owing to their processability, abundant functional groups, and network-forming capability; however, their use in highly permeable flow-through catalytic architectures remains limited. Herein, we report an interconnected gelatine/graphene oxide (GO) Pickering polyHIPE hydrogel as a biopolymer-based macromolecular scaffold for immobilising facet-engineered Pd nanocrystals toward continuous-flow Cr(VI) reduction. GO nanosheets acted as Pickering stabilisers and reinforcing components, while gelatine formed a crosslinked continuous network that preserved the emulsion-templated open-cell architecture and provided a stable matrix for Pd nanocrystal immobilisation. By regulating the GO content, internal phase volume fraction, gelatine concentration, and glutaraldehyde crosslinking density, the pore architecture was systematically controlled. Shape-controlled Pd nanocrystals were incorporated into the gelatine/GO polyHIPE matrix to examine the role of surface facets in catalytic activity. Pd nanooctahedra predominantly exposing {111} facets showed markedly faster Cr(VI) reduction than Pd nanocubes enclosed by {100} facets. When immobilised within the optimised polyHIPE hydrogel, the Pd nanooctahedra enabled efficient flow-through Cr(VI) reduction by coupling intrinsic catalytic activity with convective mass transport through the interconnected macroporous network. The monolithic reactor achieved near-complete Cr(VI) conversion at flow rates up to 10 mL h^-1 and maintained stable performance during 24 h continuous operation as well as after storage for up to 4 weeks. This study demonstrates that gelatine-based Pickering polyHIPE hydrogels can serve as structurally tunable and operationally robust macromolecular scaffolds for integrating nanocatalysts into continuous-flow water-remediation systems.