Systematic exploration of a rutile-type zinc(ii)–phosphonocarboxylate open framework: the factors that influence the structure

Abstract

To systematically explore the assembly mechanism of a rutile-type open framework of {[Zn₃(pbdc)₂]·2H₃O}_n (3) (H₄pbdc = 5-phosphonobenzene-1,3-dicarboxylic acid) constructed by 3-connected pbdc ligands and 6-connected Zn₃(CO₂)₄(PO₃)₂ secondary building units (Zn₃-SBUs), three major factors including solvothermal procedures, types of solvents and amines, are taken into consideration. Seven novel structures, namely {[Zn₅(pbdc)₂(OH)₂(H₂O)₄]·4H₂O}_n (1), {[Zn₃(pbdc)₂·H₂O]·(Htea)·H₃O·2–5(H₂O)}_n (2), {[Zn₃(pbdc)₂](H₃O)₂(dma)}_n (4), {[Zn₂(pbdc)(taea)]·3H₂O}_n (5), {[Zn₃(pbdc)₂(Hpda)₂]·2H₂O}_n (6), {[Zn₅(pbdc)₂(Hpbdc)₂]·2H₂pz·9H₂O}_n (7), {[Zn₃(pbdc)₂]·Hpd·H₃O·4H₂O}_n (8) are obtained. The results indicate that the layered-solvothermal method and the isopropanol solvent play crucial roles in the construction of the special anionic open framework of [Zn₃(pbdc)₂]²⁻. Changing these two factors led molecular assembly away from the rutile-type open framework. However, amines play a variable role in the framework, which means that by using appropriate amines, molecular assembly could generate the open framework of [Zn₃(pbdc)₂]²⁻ with pores decorated by amines. These results suggest a different approach towards decorating pores in anionic frameworks with precise structural information.