Linker-Enabled Self-Nitridation and Multistep Pyrolysis Pathways of Cu-Triazolate MOFs Toward Cu₃N/Carbon Fibers

Metal-organic framework (MOF) pyrolysis is widely used to produce functional nanomaterials, yet it is still commonly regarded as a simple thermal decomposition or templating process. Here, we show that a Cu(II)-1,2,3-triazolate (trz) MOF functions as a nanoreactor in which intrinsic metal-linker chemistry governs the evolution of both phase and morphology. Strikingly, the triazole ring remains preserved throughout the pre-pyrolysis phase transitions that lead to the formation of Cu atomic clusters. These highly reactive Cu clusters and the preserved triazolate are essential for the subsequent formation of metal nitride, as they enable efficient nitridation at an unusually low temperature. Without introducing any external nitrogen source, the Cu clusters react with NH₃ released from linker decomposition, leading to the formation of Cu₃N rather than crystallization into metallic Cu particles. By combining in situ and ex situ characterization, we show that copper, nitrogen species, and the carbonizing matrix evolve sequentially rather than independently. As a result, Cu₃N is selectively stabilized over metallic Cu within a fibrous N-doped carbon network. Beyond offering a self-nitridation route to Cu₃N, this work highlights the critical role of transient intermediates in directing MOF pyrolysis outcomes and redefines MOF pyrolysis as a chemically interactive process.