Stable Interfacial Ruthenium Species for Highly Efficient Polyolefin Upcycling

The
present polyolefin hydrogenolysis recycling cases
acknowledge
that zerovalent Ru exhibits high catalytic activity. A pivotal rationale
behind this assertion lies in the propensity of the majority of Ru
species to undergo reduction to zerovalent Ru within the hydrogenolysis
milieu. Nonetheless, the suitability of zerovalent Ru as an optimal
structural configuration for accommodating multiple elementary reactions
remains ambiguous. Here, we have constructed stable Ru0–Ruδ+ complex species, even under reaction
conditions, through surface ligand engineering of commercially available
Ru/C catalysts. Our findings unequivocally demonstrate that surface-ligated
Ru species can be stabilized in the form of a Ruδ+ state, which, in turn, engenders a perturbation of the σ bond
electron distribution within the polyolefin carbon chain, ultimately
boosting the rate-determining step of C–C scission. The optimized
catalysts reach a solid conversion rate of 609 g·gRu–1·h–1 for polyethylene.
This achievement represents a 4.18-fold enhancement relative to the
pristine Ru/C catalyst while concurrently preserving a remarkable
94% selectivity toward valued liquid alkanes. Of utmost significance,
this surface ligand engineering can be extended to the gentle mixing
of catalysts in ligand solution at room temperature, thus rendering
it amenable for swift integration into industrial processes involving
polyolefin degradation.