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Smart voltage-gated nanofiltration membranes have enormous potential for on-demand and precise separation of similar molecules, which is an essential element of sustainable water purification and resource recovery. However, the existing voltage-gated membranes are hampered by limited selectivity, stability, and scalability due to electroactive monomer dimerization. Here, for the first time, the host-guest recognition properties of cucurbit[7]uril (CB[7]) are used to protect the viologen derivatives and promote their assembly into the membrane by interfacial polymerization. Viologen functions as a voltage switch, whereas CB[7] complexation prevents its dimerization and improves its redox stability. The inhibited diffusion of the CB[7]-viologen complex enables the precise patterning of the surface structure. The resultant voltage-gated membrane displays 80% improved rejection performance, excellent recovery accuracy for similar molecules, and anti-fouling properties. This work not only provides an innovative strategy for the preparation of voltage-gated smart nanofiltration membranes but also opens up new avenues for ion-selective transmission in water treatment, bionic ion channels, and energy conversion.

Herein we describe that oxidation reactions of the dimeric cyclophosphazanes, [{P(μ-NR)} 2 (μ-NR)] 2 , R = t Bu (1), to produce a series of diagonally dioxidized products P 4 (μ-N t Bu) 6 E 2 [E = O (2), S (3), and Se (4)] and tetraoxidized frameworks. The latter display an unexpected C-N bond activation and cleavage to produce a series of novel phosphazane macrocyclic arrangements containing newly formed N-H bonds. Macromolecules P 4 (μ-N t Bu) 4 (μ-NH) 2 O 4 (5) and P 4 (μ-N t Bu) 3 (μ-NH) 3 E 4 , E = S (6) and Se (7), dicleaved and tricleaved products, respectively, are rare examples of dimeric macrocycles containing NH bridging groups. Our theoretical and experimental studies illustrate that the extent to which these C-N bonds are cleaved can be controlled by modification of steric parameters in their synthesis, by adjusting either the steric bulk of the substituents in the parent framework or the size of the chalcogen element introduced during the oxidation process. Our findings represent new synthetic pathways for the synthesis of otherwise-elusive macrocycle arrangements within the phosphazane family.

Reaction of 4-CN-PhOH with [ClP(μ-N(t)Bu)]2 (1) (2:1 ratio) in the presence of Et3N produced the functionalized cyclodiphosph(III/III)azane [(4-CN-PhO)P(μ-N(t)Bu)]2 (2). Oxidation of 2 produced cyclodiphosph(V/V)azanes [(4-CN-PhO)(E)P(μ-N(t)Bu)]2 [E = O (3), S (4), and Se (5)]. This is the first example of a series of cyclodiphosph(V/V)azane derivatives obtained from a single cyclophosph(III/III)azane precursor where all the accessible chalcogen oxidized products are air-stable over prolonged periods of time.