Regulation of NO Uptake in Flexible Ru Dimer Chain Compounds with Highly Electron Donating Dopants

On-demand design
of porous frameworks for selective capture of specific gas molecules,
including toxic gas molecules such as nitric oxide (NO), is a very
important theme in the research field of molecular porous materials.
Herein, we report the achievement of highly selective NO adsorption
through chemical doping in a framework (i.e., solid solution approach):
the highly electron donating unit [Ru2(o-OMePhCO2)4] (o-OMePhCO2– = o-anisate) was transplanted
into the structurally flexible chain framework [Ru2(4-Cl-2-OMePhCO2)4(phz)] (0; 4-Cl-2-OMePhCO2– = 4-chloro-o-anisate and phz
= phenazine) to obtain a series of doped compounds, [{Ru2(4-Cl-2-OMePhCO2)4}1–x{Ru2(o-OMePhCO2)4}x(phz)] (x =
0.34, 0.44, 0.52, 0.70, 0.81, 0.87), with [Ru2(o-OMePhCO2)4(phz)] (1) as x = 1. The original compound 1 was made purely from a “highly electron donating unit”
but had no adsorption capability for gases because of its nonporosity.
Meanwhile, the partial transplant of the electronically advantageous
[Ru2(o-OMePhCO2)4] unit with x = 0.34–0.52 in 0 successfully enhanced the selective adsorption capability of NO
in an identical structurally flexible framework; an uptake at 95 kPa
that was 1.7–3 mol/[Ru2] unit higher than that of
the original 0 compound was achieved (121 K). The solid
solution approach is an efficient means of designing purposeful porous
frameworks.