Construction of 3D Layer-Pillared Homoligand Coordination Polymers from a 2D Layered Precursor

Herein, we present a new method for preparing homoligand 3D coordination polymers. First, a layered metal−organic framework Zn3(BDC)3(H2O)2·4DMF 1 (BDC is terephthalate, DMF is N,N-dimethylformamide) was fabricated
from a H2BDC by liquid−liquid diffusion. Second, the layered product, 1, was used as a precursor to solvothermally
react with further H2BDC at 140−180 °C, resulting in two products of BDC insertion into the layered structure.
These are [Zn3(p-BDC)4]·2HPIP, 2 (HPIP is partly protonated piperazine), and [Zn3(p-BDC)3(H2BDC)]·(C6H15NO)·H2O·3DMF, 3 (C6H15NO is triethylamine N-oxide). Single-crystal X-ray diffraction shows that 2 possesses a layer-pillared structure of μ4-BDC, with 1D channels, while 3 has a layer-pillared structure of μ2-BDC, with 2D channels.
N2-sorption experiments show 3 has a relatively high BET surface area of 750 m2/g. It is proposed that 2 follows
the crystal growth mechanism of Ostwald ripening, whereas the crystal structure of 3 might be formed by an
insertion mechanism.