Upcycling of polyolefin plastics by processive catalyst

The accumulation of waste plastics has become a global catastrophe. New chemical strategies for upcycling plastics into value-added molecules are urgently needed to address this crisis. One such approach would be the highly selective cleavage of long polymer chains to form narrow distributions of shorter alkanes with controlled chain lengths for use as fuels or lubricants. Processive catalysts, which bind long-chain reactants and perform multiple catalytic cleaving events to produce short-chain products, are common in nature for the deconstruction of biomacromolecules. This idea could be advantaged in plastic upcycling chemistry to improve the efficiency and selectivity of catalytic processes. Here we show, using solid-state NMR methods, that appropriately structured mesoporous silica materials control the adsorption and conformation of polyethylene in a way that is reminiscent of processive enzymes. On the basis of these observations, we designed, constructed, and investigated a processive catalyst for the hydrogenolysis of polyethylene and other polyolefins in condensed phase. In particular, we show several characteristics of the catalysis that suggest processive behavior, distinct from that observed in a nonporous, non-processive control catalyst. We also studied the effect of catalyst design parameters on the activity and selectivity in the hydrogenolysis of polyethylene.