Spontaneous efficient degradation of polyesters in soil by an enzyme@MOF platform

Waste plastics represent a serious and growing environmental problem. Whereas biodegradable polyesters such as polycaprolactone (PCL) and polylactic acid (PLA) offer a potential solution, their spontaneous degradation takes up to 3 years in the field. Industrial composting, an alternative approach, is labor and energy intensive as well as being prone to cross-contamination by other plastics. In recent years, exploitation of bespoke enzyme systems has been shown to accelerate composting but these innovative approaches are thus far unsuitable for field deployment. We address this challenge by developing an enzyme@MOF platform to fabricate composite plastics through multiple industry-compatible processing techniques, including screw extrusion, 3D printing, and solution casting. The top performing enzyme@MOF, lipase@MIL-88A, degrades PCL and is fast (<10 days), low cost ($11/kg) and acid-responsive. The latter feature enables controlled degradation of the MOF to release lipase in the field upon exposure to weakly acidic rainwater, entirely avoiding the need for collection and composting. Further, the degradation products of lipase@MIL-88A are biocompatible and were found to fertilize plant growth. The broad utility of the enzyme@MOF approach is further demonstrated by its successful application to multiple polyester plastics, such as PLA, PET, PBAT, PBS, and PEF.