Acute Cr VI water pollution duet oa nthropogenic activities is an increasing worldwide concern. The high toxicity and mobility of Cr VI makesi tn ecessary to develop dual adsorbent/ion-reductive materialst hat are able to capture Cr VI and transform it efficiently into the less hazardous Cr III. An accurated escription of chromium speciationa tt he adsorbent/ion-reductive matrix is key to assessing whether Cr VI is completely reduced to Cr III ,o ri fi ts incomplete transformation has led to the stabilization of highly reactive, transient Cr V species within the material. With this goal in mind, a dual ultraviolet-visible and electron paramagnetic spectroscopy approachh as been applied to determine the chromium speciation within zirconium-basedm etal-organic frameworks (MOFs). Our findings point out that the generation of defects at Zr-MOFs boosts Cr VI adsorption, whilst the presence of reductiveg roups on the organic linkersp lay ak ey role in stabilizing it as isolated and/or clustered Cr III ions.

In this paper, the potential of 2D printing technologies to create thin film gas sensors from ionic liquid (IL)/metal-organic framework (MOF) composites is evaluated. To accomplish this, the MOF is synthesized solvothermally, and impregnated with the IL. The structure and basic properties of the IL/ MOF composites are characterized using thermal, spectroscopic, and X-ray diffraction techniques, and the resultant sensing capacity of the bulk material is evaluated by impedance spectroscopy. The IL/MOF systems are then integrated into a 2D printed silver capacitive circuit by spray and tested on a custom-made gas flow apparatus. Exposure of the IL/MOF based sensors to water, acetone, and ethanol induces a repetitive variation of the capacitance (from 0.05 to 7 pF) that is dependent on the nature of the gas. IL/MOF based sensors can detect changes in concentrations in the range of 10k-100k ppm in less than a second. The conclusions of this work are the first steps towards the development of 2D printed sensors based on IL/MOF materials. Such materials offer countless possibilities to tailor the porosity, chemistry, selectivity, and electrical response to make the sensor suitable to detect the desired analyte.

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