0D to 3D Pr^III metal-organic networks crystal engineered for optimal iodine adsorption

Four new praseodymium(III) metal-organic compounds varying in dimensionality from 0D to 3D have been designed and synthesized based on N-heterocyclic polycarboxylic acids, including pyridine-2,6-dicarboxylic acid (H₂pydc) and pyrazine-2,3-dicarboxylic acid (H₂pzdc). Altering the concentration of piperazine (pip, ancillary ligand) enables control over the dimensionality of the compound by switching between the 0D [H₂pip][Hpip][Pr(pydc)₃]·4H₂O (I) and the 1D {[Pr(pydc)(Hpydc)(H₂O)₂]·4H₂O}_n (II) coordination polymer (CP). Upon replacing H₂pydc with H₂pzdc, CP II is converted to the 2D CP [Pr(pzdc)(Hpzdc)(H₂O)₃]_n (III) and using the metalloligand [Zn(Hpzdc)₂(H₂O)₂]^2-, the 3D heterometallic CP {[Pr₂Zn(pzdc)₄(H₂O)₆]·2H₂O}_n (IV) is formed. Compound IV shows high stability in the absence of uncoordinated solvent molecules and is stable up to 400°C, even in the presence of humidity. Therefore, IV was utilized for iodine adsorption in the vapour phase and in the presence of humidity. The results confirm the remarkable potential of IV for reversible adsorption of iodine vapour.