Postsynthetic ligand and metal ion exchange (PSE) processes are shown to readily occur in several "inert" metal-organic frameworks (MOFs), including zeolitic imidazolate frameworks (ZIFs). Ligand exchange can occur between solid samples, as was demonstrated under relatively mild conditions with two robust, topologically distinct MOFs, MIL-53(Al) and MIL-68(In). Interestingly, ligand PSE is not observed with MIL-101(Cr), which is attributed to the kinetic inertness of the Cr(III) ion. In addition to ligand exchange, metal ion (cation) PSE was also studied between intact MOF microcrystalline particles. Metal ion transfer between MIL-53(Al) and MIL-53(Fe) was readily observed. These PSE reactions were monitored and the products characterized by a number of techniques, including aerosol time-of-flight mass spectrometry, which permits single-particle compositional analysis. To show the potential synthetic utility of this approach, the PSE process was used to prepare the first Ti(IV) analogue of the robust UiO-66(Zr) framework. Finally, experiments to rule out mechanisms other than PSE (i.e., aggregation, dissolution/recrystallization) were performed. The results demonstrate that PSE, of either ligands or cations, is common even with highly robust MOFs such as UiO-66(Zr), MILs, and ZIFs. Furthermore, it is shown that PSE is useful in preparing novel materials that cannot be obtained via other synthetic methods.

Herein, we report that the exchange of ligands from an intact metal-organic framework (MOF) can be exploited as a means to introduce functionalized ligands into MOFs under mild conditions. It is shown that ligand exchange can occur with 'inert' Zr(IV)-based UiO-66 MOFs in a solvent dependent manner. We call this process postsynthetic exchange (PSE) and show that it provides access to MOFs that are not readily prepared in high quality by solvothermal methods. It was found that ligand exchange can occur between UiO-66 MOFs as monitored by aerosol time-of-flight mass spectrometry (ATOFMS). ATOFMS was used to analyze the chemical composition of microcrystalline MOFs on the single particle level, providing information not available through bulk analysis. PSE is an important postsynthetic approach to the modification of MOFs, and the ligand exchange revealed by ATOFMS requires a re-evaluation of the assumed 'stability' of even the most robust MOFs.

Estimating the aerosol contribution to the global or regional radiative forcing can take advantage of the relationship between the spectral aerosol optical properties and the size and chemical composition of aerosol. Long term global optical measurements from observational networks or satellites can be used in such studies. Using in-situ chemical mixing state measurements can help us to constrain the limitations of such estimates.

In this study, the Absorption Ångström Exponent (AAE) and the Scattering Ångström Exponent (SAE) derived from 10 operational AERONET sites in California are combined for deducing chemical speciation based on wavelength dependence of the optical properties. In addition, in-situ optical properties and single particle chemical composition measured during three aircraft field campaigns in California between 2010 and 2011 are combined in order to validate the methodology used for the estimates of aerosol chemistry using spectral optical properties.

Results from this study indicate a dominance of mixed types in the classification leading to an underestimation of the primary sources, however secondary sources are better classified. The distinction between carbonaceous aerosols from fossil fuel and biomass burning origins is not clear, since their optical properties are similar. On the other hand, knowledge of the aerosol sources in California from chemical studies help to identify other misclassification such as the dust contribution

Herein, we report a general postsynthetic exchange (PSE) approach to introduce a redox-active transition metal, specifically Mn(II), into "inert" zeolitic imidazolate frameworks (ZIFs), a subclass of metal−organic frameworks (MOFs). It is shown that metal ion PSE occurs in ZIF-71 (RHO topology) and ZIF-8 (SOD topology) under ambient conditions. The metal exchanged ZIFs are the first porous, Mn(II)-based ZIFs and a rare example of ZIFs with two transition metal centers in a single lattice. Exchanged materials are characterized by scanning electron microscopy-energy dispersed X-ray spectroscopy (SEM-EDX), aerosol time-of-flight mass spectrometry (ATOFMS), X-ray fluorescence spectroscopy (XRF), and Brunauer−Emmett−Teller (BET) surface area analysis. In addition, stepwise "tandem" PSE strategies are described to exchange of metal ions and organic linkers consecutively in ZIFs. These findings are important for probing the chemical dynamics of ZIFs, despite their high crystallinity and robustness, and inspire the more widespread use of PSE to prepare multimetallic and multifunctional MOFs.