Tuning extreme anisotropic thermal expansion in 1D coordination polymers through metal selection and solid solutions.The thermal expansion behaviour of a series of 1D coordination polymers has been investigated.  Variation of the metal centre allows tuning of the thermal expansion behaviour from colossal positive volumetric to extreme anomalous thermal expansion.  Preparation of solid solutions increased the magnitude of the anomalous thermal expansion further, producing two species displaying supercolossal anisotropic thermal expansion (ZnCoCPHTαY2 = -712 MK-1, αY3 = 1632 MK-1 and ZnCdCPHTαY2 = -711 MK-1, αY3 = 1216 MK-1).
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