Synthesis of (sub)microcrystals of dinuclear terbium(III) carboxylate (Hpiv)6Tb2(piv)6 and polymeric terbium(III) carboxylate {Tb(piv)3}n in supercritical carbon dioxide. Photoluminescence and magnetic properties

•Coordination polymer {Tb(piv)3}n was prepared from complex (Hpiv)6Tb2(piv)6 by sc-CO2 processing.•Terbium carboxylates was prepared as single-phase (sub)microcrystals with a controlled size.•Polymer {Tb(piv)3}n can be prepared as polycrystalline aggregates with different morphologies.•Size of aggregates affects the photoluminescent and magnetic properties of terbium carboxylates.