Abstract The development and utilization of biomass resources could contribute to new materials for long‐term sustainable energy storage and environmental applications, reduce environmental impacts, and meet the urgent need for green and sustainable development strategies. Herein, a bimetallic metal–phenolic network (MPN) was applied to incorporate different metallic element species into cattle skin and fabricate collagen‐fiber‐derived complex oxide nanofibers using natural polyphenols ( Myrica tannins). Direct thermal transition of these biomass–MPN composites generates hierarchically porous nanofibers possessing micro‐ and mesoporous architectures along with a well‐preserved macroscopic structure. The pore system and complex oxide composition provide excellent photocatalytic performance. This low‐cost, simple, and readily scalable MPN‐based approach provides a straightforward route to synthesize nanostructured materials directly from biomass, which could play important roles in a wide range of potential applications.