Near Zero Thermal Expansion Coordinated with Geometric Flexibility and π…π Interaction in [Zn8(SiO4)(m-BDC)6]n
Zero thermal expansion (ZTE), lattices retaining constant upon heating, has attracted considerable interests owing to its potential technique applications. To date, intrinsic single phase ZTE or near-ZTE material is very rare. Herein, we report a near-ZTE compound, [Zn8(SiO4)(m-BDC)6]n, with a near-ZTE volumetric behavior αV = -4.35×10-6 K-1 in the temperature range of 100 ~ 475 K. Raman spectra and density functional theory (DFT) calculations demonstrate that the spring-like geometric deformation results in the anisotropic thermal expansion behavior. Further temperature dependent structural analysis and reduced density gradient (RGD) calculations evidence that the repulsion of π…π interaction leads to the contraction of the building linkage. Such synergistic effect of geometric deformation and π…π interaction gives rise to the overall volumetric near-ZTE behavior in [Zn8(SiO4)(m-BDC)6]n.