A porous scandium MOF denoted STA-27 (St Andrews Porous Material-27) has been synthesised solvothermally using the 2,3,5,6-tetrakis(4-carboxyphenyl)pyrazine anion (TCPP 4− ) as the tetratopic carboxylate linker. STA-27 possesses a unique scandium-based 1D rod secondary building unit (SBU) comprising corner-sharing scandium Sc 2 O 11 dimers connected via carboxylate groups from the linker. After activation under mild conditions STA-27 is an active Lewis acidic catalyst, while heating at elevated temperatures results in rupturing of the Sc–O–Sc linkages and a phase transition to a different topological type. Under similar synthesis conditions the smaller Al 3+ and Ga 3+ cations give isostructural MOFs with a different, previously reported, topology type based on chains of corner-sharing MO 4 (OH) 2 octahedra: the Al-form possesses attractive properties for CO 2 adsorption.