Colossal negative thermal expansion (CNTE) materials are of significant importance for applications in precision engineering and related fields. However, simultaneously achieving a colossal negative thermal expansion coefficient (CTE) and a broad temperature range remains a central challenge. Using a combination of synchrotron x-ray diffraction, Raman spectroscopy, and density-functional-theory calculations, we find that the $A_2{\mathrm{P}}_2{\mathrm{O}}_7$ ($A=\mathrm{Cu}$, Mg, Zn) series exhibits significant CNTE during the α-β phase transition. Structural analysis indicates that during the phase transition, the pronounced contraction of the axial $\mathrm{A}-\mathrm{O}{4}_{\left(\mathrm{long}\right)}$ bonds drives the lattice volume reduction. Meanwhile, temperature-dependent Raman spectroscopy reveals that the 105 $\mathrm{c}{\mathrm{m}}^{-1}$ vibrational mode, assigned to antisymmetric Cu–O bond stretching, undergoes softening accompanied by significant broadening, indicating strong electron–lattice coupling in the series. Combined with energy pathway calculations, the presence of the pseudo-Jahn–Teller effect destabilizes the high-symmetry β phase and drives its transformation into the low-symmetry α phase, thereby leading to significant volume contraction upon heating. Further analysis indicates that the shallow and flattened potential energy surface at the Cu site in ${\mathrm{Cu}}_2{\mathrm{P}}_2{\mathrm{O}}_7$ enables pronounced anti-off-centering displacement of Cu atoms with increasing temperature, which in turn leads to significant NTE before the phase transition, with a volumetric CTE of $-22.25\times {10}^{-6}{\mathrm{K}}^{-1}$. Furthermore, substituting V at the P site leads to the formation of ${\mathrm{Cu}}_2{\mathrm{V}}_2{\mathrm{O}}_7$, which exhibits a colossal negative CTE ($-858.83\times {10}^{-6}{\mathrm{K}}^{-1}$) and a broad CNTE temperature range of 100–900 K. This study not only reveals a physical driving mechanism of CNTE in the $A_2{\mathrm{P}}_2{\mathrm{O}}_7$ series, but also provides important theoretical guidance for the design of novel functional materials that combine colossal negative thermal expansion coefficients with a broad temperature range.

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• Pseudo Jahn-Teller effect
• Structural phase transition
• Structural properties
• Thermal expansion
• Density functional calculations
• Raman spectroscopy
• X-ray diffraction