Abstract Plastic wastes impose a significant environmental burden, yet chemically recycling them into valuable feedstocks remains presenting huge challenges. Herein, an energy‐saving microwave‐assisted catalysis system is reported via interfacial engineering of the catalyst layer on the microwave absorber for selective valorization of plastic wastes into hydrogen (H 2 ) and carbon nanotubes (CNTs). As proof of concept, a NiFe alloy layer coated on a microporous SiC foam (SiC@NiFe) is fabricated. The unique architecture enables directional thermal transfer from SiC to NiFe, minimizing energy losses from disordered thermal dissipation while preventing undesired contact of plastic‐SiC, thereby enhancing energy utilization efficiency and suppressing side reactions, respectively. Moreover, the increased inside pressure generated during plastic decomposition creates a favorable pressure gradient, driving efficient mass transfer into the microporous foam. Accordingly, the confined intermediates undergo sufficient contact with the NiFe catalytic layer. The resultant SiC@NiFe delivered H 2 yield of 67 mmol g plastic −1 with selectivity of 96 vol.% at 450 °C in upcycling of low‐density polyethylene (LDPE). This work presents a viable strategy for plastic waste valorization with the advantages of high efficiency and energy‐saving operation, provides valuable perspectives on addressing white pollution within the framework of the circular economy.