Metal-organic frameworks MOFs are advanced ultra-porous coordination polymers, which are hot topic in recent decade, particularly for sorption, separations, and environmental remediation. Structure of MOFs includes metal sites and organic linkers (functional groups) as potential anchors for “guest” molecules. Volatile organic sulfur compounds VOSCs contain sulfur, and in most of them its reduced form is present resulting in volatility, toxicity and noxious smell. VOSCs are common in natural gas, petroleum, fossil fuels and products of decomposition of organic matter; they are major contaminants of air and water. Diethylsulfide DES is an archetypal VOSC of simple structure, which also resembles major chemical warfare agent sulfur mustard. This is of interest to develop new spectroscopic methods to study reactions of solids with volatile hazardous compounds. Recently, we reported a new method of in-situ time-dependent ATR-FTIR spectroscopy. Here, we further develop it to allow in-situ time-dependent spectroscopic research in the flow of vapor of hazardous compound. First, we synthesized sorbents: aluminum MOFs with porphyrin linker (Al-MOF-TCPP-X where X = Cu2+, Zn2+ or H), characterized them by spectroscopic and structural methods, and activated to remove water and other impurities. Then, the obtained actAl-MOF-TCPP-X were studied for sorption of DES vapor in air, with and without common interfering molecules (water and n-pentane). In this new method, an ATR-FTIR spectrometer is upgraded with custom gas flow mini-reactor. This setup allows facile and safe work with vapors of hazardous compounds, spectroscopic identification of groups in the solid reacting with VOSCs, and determination of kinetics of sorption and desorption. Sorption of DES follows kinetic pseudo-zeroth order rate law, as found from in-situ time-dependent ATR-FTIR spectra in controlled gas flow and in-situ gravimetry. As the sorption reaction proceeds, the in-situ time-dependent IR spectra show the progressive increase of peaks due to DES “guest” molecules and shifts of peaks of the MOF as “host”. The host-guest interactions were assessed via numeric values of peak shifts; DES interacts with phenyl, carboxylate and O-H groups. The presented technique and a new flow mini-reactor for in-situ time-dependent ATR-FTIR spectroscopy are promising in studies of mechanism and kinetics of sorption of gases and vapors, and particularly well-suited for research of volatile and hazardous chemicals.

In-situ time-dependent ATR-FTIR spectroscopy in controlled gas flow: Mechanistic anid kinetic study of reaction of nanoporous coordination polymer metal-organic framework with hazardous organo-sulfur compound

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