Electrosorption and capacitive deionization technologies can be effective processes in removing heavy metal for water purification, wastewater treatment, resource recovery, and environmental remediation.

Electro‐responsive functional materials can play a critical role in selective metal recovery and recycling due to the need for molecular differentiation between transition metals in complex mixtures. Redox‐active metallopolymers are a promising platform for electrochemical separations, offering versatile structural tuning and fast electron transfer. First, through a judicious selection of polymer structure between a main‐chain metallopolymer (polyferrocenylsilane) and a pendant‐group metallopolymer (polyvinylferrocene), charge‐transfer interactions and binding strength toward competing metal ions are tuned, which as a result, dictate selectivity. For example, almost an order of magnitude increase in separation factor between chromate and meta‐vanadate can be achieved, depending on polymer structure. Second, these metallopolymer electrodes exhibit potential‐dependent selectivity that can even flip ion preference, based solely on electrical means—indicating a control parameter that is orthogonal to structural modifications. Finally, this work presents a framework for evaluating electrochemical separations in multicomponent ion mixtures and elucidates the underlying charge‐transfer mechanisms resulting in molecular selectivity through a combination of spectroscopy and electronic structure calculations. The findings demonstrate the applicability of redox‐metallopolymers in tailored electrochemical separations for environmental remediation, value‐added metal recovery, waste recycling, and even mining processing.

We present the crystal structure, diborane (B 2 H 6 ) and triborane (B 3 H n ) evolution, and dehydrogenation kinetics, of both bulk and nanoconfined Li/Mg(BH 4 ) 3 in a highly ordered nanoporous carbon template. The bialkali borohydride Li/Mg(BH 4 ) 3 mainly forms a structure similar to that of α-Mg(BH 4 ) 2 . The decomposition temperature of Li/Mg(BH 4 ) 3 lies between that of LiBH 4 and Mg(BH 4 ) 2 . A direct line-of-site residual gas analyzer mass spectrometer shows that very little diborane and no detectable triborane are released during the decomposition of bulk Li/Mg(BH 4 ) 3 , which is quite different from Mg(BH 4 ) 2 or LiBH 4 , indicating that the dual-cation borohydride undergoes a different decomposition pathway, and that the reaction pathway related to diborane or triborane formation was suppressed. The nanoconfined Li/Mg(BH 4 ) 3 shows a higher cycling capacity as well as a lower decomposition temperature but, in contrast, produces more diborane and triborane in comparison with bulk Li/ Mg(BH 4 ) 3 .

In article number 2009307, Xiao Su and co‐workers show that redox‐metallopolymers demonstrate both structure and electric potential‐dependent selectivity between transition metal oxyanions, offering strategies for orthogonal control in electrochemical separations. These redox‐responsive materials are a promising platform for critical element recovery and environmental remediation, especially in multicomponent ion mixtures.