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

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 Cu₂O/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.