A Porous Coordination Polymer Showing Guest-Amplified Positive and Negative Thermal Expansion.

A solvothermal reaction of Zn(NO) and 4-(1-pyrazol-4-yl)benzoic acid (Hpba) with toluene (Tol) as the template yielded a porous coordination polymer, [Zn(pba)]·0.5Tol, possessing a three-dimensional (3D) fence-like coordination framework based on inclined two-dimensional (2D) fence-like coordination layers. By virtue of the classic deformation mode of the 2D/3D fence structures, the guest-free structure exhibits very large positive thermal expansion of 347 MK and moderate negative thermal expansion of -63/-83 MK, which are remarkably enhanced to new records of 689 and -171/-249 MK, respectively, by inclusion of Tol.