Abstract
Control of the thermomechanical properties of functional materials is of great fundamental and technological significance, with the achievement of zero or negative thermal expansion behavior being a key goal for various applications. A dynamic, reversible mode of control is demonstrated for the first time in two Prussian blue derivative frameworks whose coefficients of thermal expansion are tuned continuously from negative to positive values by varying the concentration of adsorbed CO2. A simple empirical model that captures site-specific guest contributions to the framework expansion is derived, and displays excellent agreement with the observed lattice behaviour.
Highlights
The solution was allowed to stand for 24 h before the precipitate was filtered and washed with water (100 mL), followed by ethanol (100 mL), and dried in air to yield Fe3[Co(CN)6]2·xH2O as a pale yellow powder (1.76 g; x ≈ 10; yield ~89%)
NPD data were collected in the angular range 17° < 2θ < 137° at various temperature intervals upon heating, with the sample temperature stabilised within 1 K of the set point prior to data acquisition
A Hiden Isochema IMI manometric dosing system was used to dose the sample cumulatively with aliquots of CO2 gas loaded into a dosing manifold of calibrated volume, allowing the quantity of gas in each dose to be determined from the manifold pressure
Summary
The solution was allowed to stand for 24 h before the precipitate was filtered and washed with water (100 mL), followed by ethanol (100 mL), and dried in air to yield Fe3[Co(CN)6]2·xH2O as a pale yellow powder (1.76 g; x ≈ 10; yield ~89%). A solution of Na2[FeII (CN)5NO]·2H2O (1.000 g, 3.36 mmol) in 200 mL deionised water was stirred until fully dissolved, followed by addition of Co(NO3)2·6H2O (0.978 g, 3.36 mmol) to the stirred solution. The product was washed four times by adding fresh deionised water, agitating by hand and repeating the centrifuge procedure.
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