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The removal of highly toxic, ultra-dilute contaminants of concern has been a primary challenge for clean water technologies. Chromium and arsenic are among the most prevalent heavy metal pollutants in urban and agricultural waters, with current separation processes having severe limitations due to lack of molecular selectivity. Here, we report redox-active metallopolymer electrodes for the selective electrochemical removal of chromium and arsenic. An uptake greater than 100 mg Cr/g adsorbent can be achieved electrochemically, with a 99% reversible working capacity, with the bound chromium ions released in the less harmful trivalent form. Furthermore, we study the metallopolymer response during electrochemical modulation by in situ transmission electron microscopy. The underlying mechanisms for molecular selectivity are investigated through electronic structure calculations, indicating a strong charge transfer to the heavy metal oxyanions. Finally, chromium and arsenic are remediated efficiently at concentrations as low as 100 ppb, in the presence of over 200-fold excess competing salts.

Carbon capture, utilization, and storage technologies are needed to meet carbon emission reduction targets and prepare the energy industry for a carbon constrained world. Recent breakthroughs have identified the first liquid phase sorbents for CO2 capture at high temperatures. In this work, the material design space of the molten alkali metal borates (A x B1–x O1.5–x ) is explored finding sodium and sodium-rich lithium–sodium borates with a mixing ratio, x, of around 0.75 to be optimal. A mechanistic understanding of the material is developed through exploration of the sodium borate phase diagram, the development of a kinetic equilibrium model, and estimation of effective diffusion coefficients. Interesting features of the sorbents, such as the proposed formation of dicarbonate ions and counter-intuitive trends in the diffusion coefficient, are identified and explained with implications for the design of future high temperature carbon capture facilities discussed.

Molten ionic oxides based on sodium borate and mixed alkali-metal borates show remarkably fast sorption kinetics and intrinsic regenerability as liquid absorbents for CO2 capture at medium to high temperatures

The processes that produce CO 2 and other acid gases (SO x , NO x , and H 2 S) generate value for society. However, these gases are environmental pollutants, and their emission into the atmosphere undermines the value they create. In the face of climate change, CO 2 emissions require attention on an unprecedented scale. Abatement technologies focused on carbon capture, storage, and utilization (CCUS) enable the continued use of processes and resources that produce CO 2 (and other acid gases) while minimizing their effect on the environment. This review explores the role sorbents play in emission abatement and the acid gas "economy". We identify 15 sorbent categories, evaluating their performance at both the material and the system levels. We conclude with anticipated research opportunities and future trends in acid gas separation.

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Materials designed for CO 2 capture provide both an opportunity and a challenge in that industrial emissions typically contain an assortment of acid gasses, which may include SO x and NO x alongside CO 2 . Growing pressure to reduce emissions of all acid gasses, CO 2 included, presents an opportunity for simultaneous capture and a challenge in handling the resultant products. Molten alkali metal borates embody a new class of hightemperature liquid-phase materials for carbon dioxide capture and we propose here that they can also be used to address the more general challenge of acid gas capture. We examine the melt capture performance at industrially relevant concentrations and mixtures, identifying the various reaction mechanisms and products, and propose designs for separating these products efficiently at high temperatures, so that they outperform the stateof-the-art CO 2 capture technologies in handling this opportunity challenge. We also discuss the conditions to avoid and the challenges that lie ahead for these materials in the context of emission reduction and environmental protection.

The molten alkali metal borates represent an opportunity for carbon dioxide capture and the on-going challenge of adapting to a carbonconstrained world with the immediacy of climate change. We demonstrate the performance of this new class of materials at the bench scale, highlighting the ability to operate isothermally at high temperatures through the use of steam as a sweep gas. Breakthrough curves for a wide set of conditions are presented and linked to the sorbents' underlying thermodynamic and kinetic properties. We demonstrate the ability to capture over 99.9% of incoming CO 2 even at low concentrations or to capture ∼90% CO 2 under high flow rates and utilize a greater portion of the sorbent capacity. The advantages of the molten alkali metal borates scale well, and their unique position as high-temperature liquid phase sorbents may enable new process designs for efficient low-cost CO 2 capture facilities.