Integrating functional nanomaterials on nonplanar organisms has emerged as a rising technology, while significant mismatch would cause interface failure and poor durability. Herein, we demonstrate a facile strategy to assemble crystalline catecholate frameworks with honeycomb lattice on seaweed-derived polysaccharide microfibers, which is expected to form biomimetic connections and maintain durable stability. By physiological coagulation, well-aligned ZnO nanoarrays are tightly attached on alginate fibers, which is fractionally adopted as sacrifice for heteroepitaxial growth of zinc-catecholate frameworks (Zn₃(HHTP)₂). Benefiting from amplification effect of in-situ formed heterojunctions, promoted interfacial charge transfer is achieved, which allows for fabricating broadband photodetectors. Combined with high porosity for gas adsorption, the heteroepitaxial catecholate framework further enables its use as highly selective ppb-level triethylamine sensors. This work provides a promising strategy for heteroepitaxial growth of catecholate frameworks on organo-substrates and opens new applications in wearable sensor platform based on comfortable biofibers.