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The capture and separation of CO2 is an important means to solve the problem of global warming. MOFs (metal–organic frameworks) are considered ideal candidates for capturing CO2, where the adsorption enthalpy is a crucial indicator for the screening of materials. For this purpose, we propose a new minimalist solution using QCM (quartz crystal microbalance) to extract the CO2 adsorption enthalpy on MOFs. Three kinds of MOFs with different properties, sizes and morphologies were employed to study the adsorption enthalpy of CO2 using a QCM platform and a commercial gas sorption analyzer. A Gaussian simulation calculation and previously data reported were used for comparison. It was found that the measuring errors were between 5.4% and 6.8%, proving the reliability and versatility of our new method. This low-cost, easy-to-use, and high-accuracy method will provide a rapid screening solution for CO2 adsorption materials, and it has potential in the evaluation of the adsorption of other gases. [ABSTRACT FROM AUTHOR]

There is an urgent need for effective and portable gas sensors toward organophosphorus (OP) vapors in the areas of anti-terrorism and pesticides residue monitoring. Herein, we report a series of urea-functionalized SBA-15 (UXs/SBA-15: U1/SBA-15, U2/SBA-15 and U3/SBA-15) prepared by post-grafting methods and their applications in trace-level dimethyl methylphosphonate (DMMP, lab simulate of toxic OP agents) sensing by means of quartz crystal microbalance (QCM) transducers. U3/SBA-15 based QCM sensors exhibited excellent responses and remarkable selectivity toward DMMP vapors. A frequency shift (Δ F ) of −50 Hz was achieved when the DMMP vapors reached 30 ppb. And the limit of detection (LOD) of QCM sensor modified with U3/SBA-15 was found at 12.25 ppb. Moreover, the simulated adsorption enthalpies (Δ H ) of UXs and DMMP molecules were calculated with Gaussian 09 to investigate the sensing mechanism. The results indicated the existence of chemisorption between UXs and DMMP molecules caused by hydrogen-bonding interactions, among which a minimum Δ H (−71.96 kJ mol −1 ) between U3 and DMMP molecule was found, resulting a maximum response to DMMP compared with U1-DMMP (−52.53 kJ mol −1 ) and U2-DMMP (−57.01 kJ mol −1 ). Therefore, the well-defined UXs/SBA-15 lead to a great potential on the detection of OP vapors. [ABSTRACT FROM AUTHOR]

Abstract: This paper employed a measurement of quartz crystal microbalance (QCM) to investigate the effects of mesopore structures and amount of organic loadings of fluoroalcohol derivatives/SBA-15 (a kind of ordered mesoporous silica sieve) hybrids on the sensing behavior of nerve agent simulant DMMP (dimethyl methylphosphonate). The meso-structure and functional groups of silica-based mesoporous hybrids were examined by SAXS, TEM, N2 adsorption–desorption isotherms and elemental analysis. The results show that much higher response value and sensitivity are achieved when the hybrid materials have relative higher pore volume and surface area. However, this effect only appears when the mesoporous hybrids have well-ordered porous structure, indicating that ordered meso-structure is critical in fabricating high-performance DMMP sensors. The reason is likely that the ordered meso-structure not only provides a larger number of contactable HFIP groups, but also facilitates molecules diffusion in porous structure. On the other hand, the specific interaction between HFIP/SBA-15 hybrids and DMMP vapor is greatly enhanced as the amount of fluoroalcohol derivatives increases. Therefore, the amount of organic functional groups incorporated plays an important role in determining the selectivity of sensors. [Copyright &y& Elsevier]