A Family of Porous Lonsdaleite‑e Networks Obtained through Pillaring of Decorated Kagomé Lattice Sheets

A new and versatile class of metal–organic
materials (MOMs)
with augmented lonsdaleite-e (lon-e-a) topology is presented
herein. This family of lon-e nets are built by pillaring
of hexagonal two-dimensional kagomé (kag) lattices
constructed from well-known [Zn2(CO2R)4] paddlewheel molecular building blocks (MBBs) connected by 1,3-benzenedicarboxylate
(bdc2–) linkers. The pillars are [Cr3(μ3-O)­(RCO2)]6 trigonal prismatic
primary MBBs decorated by six pyridyl moieties (tp-PMBB-1). The three-fold
symmetry (D3h) of tp-PMBB-1
is complementary with the alternating orientation of the axial sites
of the paddlewheel MBBs and enables triple cross-linking of the kag layers by each pillar. These MOMs represent the first
examples of axial-to-axial pillared undulating kag layers,
and they are readily fine-tuned because the bdc2– moieties can be varied at their 5-position without changing the
overall structure. This lon-e platform possesses functionalized
hexagonal channels since the kag lattices are necessarily
eclipsed. The effects of the substituent at the 5-positions of the
bdc2– linkers upon gas adsorption, particularly
the heats of adsorption of carbon dioxide and methane, were studied.