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 [Ru-2(o-OMePhCO2)(4)] (o-OMePhCO2- = o-anisate) was transplanted into the structurally flexible chain framework [Ru-2(4-Cl-2-O-MePhCO2)(4)(phz)] (0; 4-Cl-2-OMePhCO2- = 4-chloro-o-anisate and phz = phenazine) to obtain a series of doped compounds, [{Ru-2(4-Cl-2-OMePhCO2)(4)}(1-x){Ru-2(o-OMePhCO2)(4)}(x)(phz)] (x = 0.34, 0.44, 0.52, 0.70, 0.81, 0.87), with [Ru-2(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 [Ru-2(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/[Ru-2] 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.