Enhancement of the guest orderliness in a low-symmetric perovskite-type metal-organic framework influenced by Jahn-Teller distortion.

Copper guanidinium formate (CuGF) is an ABX3-type metal-organic framework bearing a polar space group, housing a guest-host connectivity between the guanidinium and formate ions. With the maiden data-set based on single-crystal neutron diffraction, we report the discovery of the guest orderliness which surprisingly accommodates an enhancement for low-symmetric CuGF, while the scenario is contrasting for the high-symmetric Mn cousin. We provide an in-depth evaluation of the inter-guanidinium scheme and thus propose the mechanism behind this unusual effect.