Revealing Structure–Property Coupling During Thermal Conversion of Metal–Organic Frameworks

ABSTRACT Metal–organic frameworks (MOFs) provide powerful templates for constructing porous inorganic materials, yet the nanoscale thermal conversion pathways remain unclear. We reveal the mechanistic origins of structure–property emergence during thermal transformation of Cu‐BTC (HKUST‐1 MOF) into nanoporous copper oxides, uncovering transient nanocomposite states that dictate the mechanical and optoelectronic properties. By integrating various characterization techniques, we establish a unified multiscale framework linking phase evolution, pore architecture, nanomechanics, and electronic structure. Controlled calcination (300°C–500°C) transforms MOF to nanoporous oxide with non‐monotonic mechanical evolution. At 300°C, partial decomposition produces a heterogeneous Cu 2 O/CuO‐carbon nanocomposite that retains mesostructural connectivity and exhibits high local Young's modulus (∼41 GPa). This reinforcement arises from residual carbon networks, heterophase interfaces, and mesoporosity. At 500°C, phase‐pure porous CuO forms with improved optical absorption but reduced stiffness due to pore coarsening and sintering. These results reveal that functional performance in MOF‐derived oxides is not simply governed by bulk phase composition but by transient nanoscale connectivity and heterogeneity formed during partial conversion. This establishes a structure–property–function paradigm for MOF‐templated oxides, demonstrating that controlled intermediate states provide a powerful route for engineering mechanically robust and optoelectronically active nanoporous semiconductors for catalysis, sensing, and energy conversion applications.