Weather and climate extremes are critical drivers for deadly and costly natural disasters (IFRC, 2020; UN-DRR, 2020). Understanding their changes and causes have been staying high on the agenda of climate science and risk management sectors (Chen, Moufouma-Okia, et al., 2018). There is rising awareness that the impact of spatially and/or temporally correlated events tends to be disproportionately larger than that of singular hazards as well as the sum of them (Zscheischler et al., 2018). A new paradigm that moves beyond isolated extremes is therefore strongly advocated (Leonard et al., 2014). Compound events were for first time defined in a special report from the Intergovernmental Panel on Climate Change (SREX, Field et al., 2012) as multiple extreme or nonextreme events occurring (1) simultaneously at the same place; (2) concurrently across multiple regions; or (3) in rapid sequence, in the same location. The definition was further refined (Leonard et al., 2014; Zscheischler et al., 2018), with a typology recently proposed (AghaKouchak et al., 2018; Zscheischler et al., 2020). As this field burgeons, a growing body of studies has explored statistical frameworks, observed and projected changes, and attribution of diverse compound events, such as drought-heatwave (Alizadeh et al., 2020; Hao et al., 2013), costal floods combining heavy precipitation, high water level and storm surge (Wahl et al., 2015), and concurrent heatwaves across global breadbaskets

Development of technologies for protection against chemical warfare agents (CWAs) is critically important. Recently, polyoxometalates have attracted attention as potential catalysts for nerve-agent decomposition. Improvement of their effectiveness in real operating conditions requires an atomic-level understanding of CWA decomposition at the gas–solid interface. We investigated decomposition of the nerve agent Sarin and its simulant, dimethyl chlorophosphate (DMCP), by zirconium polytungstate. Using a multimodal approach, we showed that upon DMCP and Sarin exposure the dimeric tungstate undergoes monomerization, making coordinatively unsaturated Zr­(IV) centers available, which activate nucleophilic hydrolysis. Further, DMCP is shown to be a good model system of reduced toxicity for studies of CWA deactivation at the gas–solid interface.

The threat of chemical warfare agents (CWAs), assured by their ease of synthesis and effectiveness as a terrorizing weapon, will persist long after the once-tremendous stockpiles in the U.S. and elsewhere are finally destroyed. As such, soldier and civilian protection, battlefield decontamination, and environmental remediation from CWAs remain top national security priorities. New chemical approaches for the fast and complete destruction of CWAs have been an active field of research for many decades, and new technologies have generated immense interest. In particular, our research team and others have shown metal–organic frameworks (MOFs) and polyoxometalates (POMs) to be active for sequestering CWAs and even catalyzing the rapid hydrolysis of agents. In this Forum Article, we highlight recent advancements made in the understanding and evaluation of POMs and Zr-based MOFs as CWA decontamination materials. Specifically, our aim is to bridge the gap between controlled, solution-phase laboratory studies and real-world or battlefield-like conditions by examining agent–material interactions at the gas–solid interface utilizing a multimodal experimental and computational approach. Herein, we report our progress in addressing the following research goals: (1) elucidating molecular-level mechanisms of the adsorption, diffusion, and reaction of CWA and CWA simulants within a series of Zr-based MOFs, such as UiO-66, MOF-808, and NU-1000, and POMs, including Cs8Nb6O19 and (Et2NH2)8[(α-PW11O39Zr­(μ-OH)­(H2O))2]·7H2O, (2) probing the effects that common ambient gases, such as CO2, SO2, and NO2, have on the efficacy of the MOF and POM materials for CWA destruction, and (3) using CWA simulant results to develop hypotheses for live agent chemistry. Key hypotheses are then tested with targeted live agent studies. Overall, our collaborative effort has provided insight into the fundamental aspects of agent–material interactions and revealed strategies for new catalyst development.

CdTe/CdSe nanocrystal (NC) solar cells with an inverted structure (ITO/ZnO/CdSe/CdTe/Au) have been successfully fabricated by a simple solution process coupled with layer-by-layer sintering techniques. It was found that the device performance is strongly dependent on the annealing strategy, the thickness of the acceptor layer and on the buffer layer of ZnO when the optimal thickness of CdTe is adopted. Without the ZnO buffer layer, a thin film of the CdSeNCs on an ITO substrate shows a rougher morphology, resulting in device shunting. However, when a 40 nm-thick ZnO buffer layer and 60 nm-thick CdSe were employed, the device shows a much higher PCE of 5.81% under device conditions, post-annealing at 340 8C. This value is the highest efficiency ever reported to date for a CdTe/CdSe NC solar cell. Comparing with CdTe/CdSe NC solar cells with the normal device configuration, this device with an inverted structure simultaneously offers good Ohmic contact for carrier collection and efficient harvesting of solar photons in a wide wavelength.

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Developing novel and more efficient filters for chemical warfare agent (CWA) decomposition remains an important challenge for modern technology due to the continuous threat those weapons present in the event of use. Recently, metal−organic frameworks (MOFs) have attracted attention as potential catalysts for nerve agent decomposition. However, in order to improve their performance under battlefield conditions, it is crucial to understand the influence of ambient contaminants such as carbon dioxide on CWA adsorption and decomposition. Here, we present a comprehensive experimental and computational study on the influence of CO 2 on the adsorption and decomposition of the CWA simulant dimethyl methyl phosphonate (DMMP) by the Zr-based MOF-808. The study combined in situ synchrotron powder X-ray diffraction (PXRD) with variable-temperature infrared spectroscopy (VTIR) and computations. PXRD and experiments with pure CO 2 revealed that the MOF framework contracts by 0.2% after CO 2 saturation and CO 2 adsorbs within the MOF-808 framework via dispersion forces with an enthalpy of adsorption of −32.2 ± 1.8 kJ/mol. From five DRIFTS experiments conducted in various gas flow regimes we established that CO 2 interferes with the decomposition of DMMP due to the formation of carbonate species, while if it is used as a regeneration agent, it accelerates the desorption of DMMP and DMMP decomposition products. In situ PXRD experiments showed that CO 2 also limited expansion of the framework due to the formation of carbonate species by 40% in comparison to values in a control experiment with N 2 . The main conclusions of the computational study are (a) CO 2 reversibly adsorbs onto MOF-808 via both μ 3 -OH groups located within the tetrahedral pores of the MOF and/or to the MOF surface with stabilizing dispersion interactions, (b) the presence of DMMP provides stability to the CO 2 −(μ 3 -OH) moiety, which hinders the μ 3 -OH transfer to the DMMP molecule required for the nerve-agent decomposition until the carbonyl to carbonate transformation is completed, and (c) CO 2 molecules are not sufficient for the regeneration of the MOF when DMMP decomposition products are present but rather there is desorption of bound DMMP.

We developed novel hybrid ligands to passivate PbS colloidal quantum dots (CQDs), and two kinds of solar cells based on as-synthesized CQDs were fabricated to verify the passivation effects of the ligands. It was found that the ligands strongly affected the optical and electrical properties of CQDs, and the performances of solar cells were enhanced strongly. The optimized hybrid ligands, oleic amine/octyl-phosphine acid/CdCl2 improved power conversion efficiency (PCE) to much higher of 3.72 % for Schottky diode cell and 5.04 % for p–n junction cell. These results may be beneficial to design passivation strategy for low-cost and high-performance CQDs solar cells.

This Review summarizes the recent progress made in the field of chemical threat reduction by utilizing new in situ analytical techniques and combinations thereof to study multifunctional materials designed for capture and decomposition of nerve gases and their simulants. The emphasis is on the use of in situ experiments that simulate realistic operating conditions (solid–gas interface, ambient pressures and temperatures, time-resolved measurements) and advanced synchrotron methods, such as in situ X-ray absorption and scattering methods, a combination thereof with other complementary measurements (e.g., XPS, Raman, DRIFTS, NMR), and theoretical modeling. The examples presented in this Review range from studies of the adsorption and decomposition of nerve agents and their simulants on Zr-based metal organic frameworks to Nb and Zr-based polyoxometalates and metal (hydro)­oxide materials. The approaches employed in these studies ultimately demonstrate how advanced synchrotron-based in situ X-ray absorption spectroscopy and diffraction can be exploited to develop an atomic- level understanding of interfacial binding and reaction of chemical warfare agents, which impacts the development of novel filtration media and other protective materials.