An isostructural solid solution series of one-dimensional coordination polymers, [(Ru(1-x)Rhx)(2)(2,4,5-Me3PhCO2)(4)(phz)] (x = 0, 0.1, 0.22, 0.39, 0.55, and 1; 2,4,5-Me3PhCO2- = 2,4,5-trimethylbenzoate; phz = phenazine), was prepared by mixing [Rh-2(II,II)(2,4,5-Me3PhCO2)(4)] with [Ru-2(II,II)(2,4,5-Me3PhCO2)(4)] in x:(1 - x) reaction ratios, respectively. This series of compounds systematically tunes the gate-opening pressures for the adsorption of CO2 (195 K) and NO (121 K), suggesting a feasible and simple method to modulate the gate-opening pressures.