An in situ investigation of the thermal decomposition of metal-organic framework NH2-MIL-125 (Ti)

Titanium based metal-organic frameworks (MOFs) are interesting self-sacrificial precursors to derive semiconducting porous nanocomposites for highly efficient heterogeneous catalysis. However, there is a lack of systematic and in-depth mechanistic understanding the pyrolytic conversion MOF into desired functional composite materials. In this work, TGA-MS in situ STEM/EDX combined with other characterization techniques were employed investigate evolution structural, physicochemical, textural morphological properties NH2-MIL-125(Ti) pyrolysis at different temperatures an inert gaseous atmosphere. thermal analysis reveals presence 3 rather defined stages transformation following order: phase-pure, crystalline ? intermediate amorphous phase without accessible porosity recrystallized phase. The three occur from room temperature till 300 °C, between 350 550 °C above ~550 respectively. It found that framework starts collapse around accompanied cleavage coordination covalent bonds organic linkers [O2C–C6H3(NH2)–CO2]6 Ti oxo-cluster Ti8O8(OH)4. linker continues fragmentation 450 causing shrinkage particle sizes. dominant pore size 0.7 nm gradually expands 1.4 800 along formation mesopores. derived disc-like particles exhibit approximately 35% volume compared pristine precursor. Highly N and/or C self-doped TiO2 nanoparticles homogeneously distributed carbon matrix. original 3D tetragonal morphology remains preserved doped TiO2/C composites. This study will provide behavior MOFs rationally select design composites relevant applications.