Atom-economy upcycling of commodity thermoset polyurethane into photocuring 3D printing resins based on selective cleavage-crosslink strategy.

Polyurethane waste poses significant environmental challenges due to its large bulk volume and thermoset nature. Current recycling methods suffer from high reagent consumption, urethane byproduct generation, and limited economic value. Here, we well address these issues through a selective cleavage-crosslink strategy using food-grade ethyl acetoacetate (EAA) to break biuret crosslinks while preserving urethane/urea bonds in non-crosslinked regions virtually intact. This strategy minimizes reagent consumption and avoids urethane byproduct. Importantly, the deconstructed product can be fully upcycled to high value-added photocuring 3D printing products with an exceptionally high waste content (up to ~90%) and excellent mechanical properties. Beyond 3D printing, the deconstructed product also holds potential as raw material for adhesives, PU synthesis, and epoxy modifiers. This strategy uses inexpensive commercial reagents and requires no modification to existing polyurethane infrastructure, establishing a commercially implementable pathway for polyurethane waste recycling.