Multi-heterogeneous oxide sensing layers, i.e., NiO/Fe2O3 catalyst loaded SnO2 fiber-in-tube nanostructures (NiO/Fe2O3-FITs), were rationally synthesized from an electrospinning solution containing a bio-inspired chitosan-bimetal complex template. The NiO/Fe2O3-FITs showed remarkably enhanced sensing properties and superior cross-sensitivity toward sub-ppm levels of formaldehyde.