LAUSR

Carbon materials are essential to the development of modern society with indispensable use in various applications, such as energy storage and high‐performance composites. Despite great progress, on‐demand carbon manufacturing with control over 3D macroscopic configuration is still an intractable challenge, hindering their direct use in many areas requiring structured materials and products. This work introduces a simple and scalable method to generate complex, large‐scale carbon structures using easily accessible materials and technologies. 3D‐printed, commercial polypropylene (PP) parts can be thermally stabilized through cracking‐facilitated diffusion and crosslinking. The newly elucidated mechanism from this work allows thick PP parts to yield carbonaceous products with complex structures through a subsequent pyrolysis step. The approach for enabling PP‐to‐carbon conversion has consistent product yield and controlled dimensional shrinkage. Under optimized processing conditions, these PP‐derived carbons exhibit robust mechanical properties and excellent joule heating performance, demonstrated by their versatile use as heating elements. Furthermore, this process can be extended to recycled PP, enabling the conversion of waste plastic materials to value‐added products. This work provides an innovative approach to create structured carbon materials with direct access to complex geometry, which can be transformative to, and broadly benefit, many important technological applications.