Immobilizing enzymes within metal-organic frameworks (MOFs) enables enzymes to against extreme environments. However, these MOF shells are just like armors, protective but heavy, which shield the enzymes from threats while locking them in the cage. The exploitation of immobilization strategy and intrinsic property of MOFs themselves is of great significance. Here, we proposed a functional protein trap strategy for efficient enzyme encapsulation. The ferrocenedicarboxylic acid (Fc) was used to induce the formation of defect-rich Co-based MOFs (CoBDC-Fc). As result, the engineered protein trap can not only improve the enzyme loading but also accelerate catalytic efficiency. Specifically, the atomically dispersed Fc sites serve as cocatalysts/cofactors and even change the conformation of enzymes in the construed microenvironment. Furthermore, the obtained CoBDC-Fc/enzyme exhibits excellent recyclability and tolerance to inhospitable conditions. Benefited by these, the CoBDC-Fc/enzyme/antigen composites were further prepared for cascade enzyme-linked immunosorbent assay of prostate-specific antigen with satisfactory sensitivity.