Catalytic systems designed to reproduce essential structural or mechanistic features of enzyme active sites constitute biomimetic catalysis. The catalyst is abiotic—typically a metal complex, a porous framework, or a designed organic host—yet it implements first-coordination-sphere ligands, second-sphere hydrogen bonds, or confinement that parallel those of a metalloenzyme. Porous metal–organic frameworks provide isolated, structurally defined sites that function as heterogeneous biomimetic catalysts ^[1]. Bioinspired framework catalysts span the continuum from immobilized enzymes to wholly synthetic mimics in which the framework itself is the catalyst ^[2]. Metalloporphyrin-containing MOFs illustrate biomimetic oxidation catalysis in which a heme-like iron center is held in a porous lattice ^[3]. The defining criterion is mechanistic or structural analogy to a biological catalyst, not merely high activity: a conventional solid acid or a simple metal salt is not biomimetic unless it is organized to copy an enzymatic binding or activation motif. The concept therefore lies between enzymatic catalysis and ordinary chemocatalysis, bounded by the requirement of an enzyme-inspired active-site design.