Engineering the Activity‐Selectivity Balance in Biomimetic MOF Nanozymes via Amino Acid‐Induced Pore Confinement

Achieving enzyme‐like substrate selectivity in nanozymes remains a critical challenge that restricts their analytical reliability in practical sensing. Inspired by the nanoconfined active pockets of metalloenzymes, we engineered amino acid‐modulated MIL‐101(Fe) nanozymes to tailor substrate discrimination and elucidate the distinct regulatory roles of individual amino acids. Among the four amino acids investigated (cysteine (Cys), histidine (His), aspartic acid (Asp), and proline (Pro)), Cys‐MIL‐101(Fe) introduces the most pronounced spatial gating effect by refining pore microenvironments, thereby achieving substantially enhanced substrate selectivity despite reduced catalytic activity. In contrast, His modification affords the highest catalytic activity but only moderate discrimination capability, while Asp and Pro cause limited modulation. Further sensing results demonstrate that Cys‐MIL‐101(Fe) affords up to a tenfold improvement in pesticide differentiation relative to the pristine MOF, whereas the His‐modified analogue provides only a fivefold enhancement. These results reveal that different amino acids exert distinct influences on the activity‐selectivity balance of nanozymes and show that, in multi‐target analytic discrimination, selectivity can provide an additional and sometimes dominant contribution to sensing performance. This work establishes a new paradigm for selectivity‐oriented nanozyme engineering, demonstrating that sacrificing activity can, counterintuitively, improve analytical precision.