A Family of Porous Lonsdaleite‑e Networks Obtained
through Pillaring of Decorated Kagomé Lattice Sheets
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Abstract
A new and versatile class of metal–organic
materials (MOMs)
with augmented lonsdaleite-e (<b>lon-e</b>-a) topology is presented
herein. This family of <b>lon-e</b> nets are built by pillaring
of hexagonal two-dimensional kagomé (<b>kag</b>) lattices
constructed from well-known [Zn<sub>2</sub>(CO<sub>2</sub>R)<sub>4</sub>] paddlewheel molecular building blocks (MBBs) connected by 1,3-benzenedicarboxylate
(bdc<sup>2–</sup>) linkers. The pillars are [Cr<sub>3</sub>(μ<sub>3</sub>-O)(RCO<sub>2</sub>)]<sub>6</sub> trigonal prismatic
primary MBBs decorated by six pyridyl moieties (tp-PMBB-1). The three-fold
symmetry (<i>D</i><sub>3<i>h</i></sub>) 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 <b>kag</b> layers by each pillar. These MOMs represent the first
examples of axial-to-axial pillared undulating <b>kag</b> layers,
and they are readily fine-tuned because the bdc<sup>2–</sup> moieties can be varied at their 5-position without changing the
overall structure. This <b>lon-e</b> platform possesses functionalized
hexagonal channels since the <b>kag</b> lattices are necessarily
eclipsed. The effects of the substituent at the 5-positions of the
bdc<sup>2–</sup> linkers upon gas adsorption, particularly
the heats of adsorption of carbon dioxide and methane, were studied