Scheme 1 (a) Possible degradation intermediate of diglyme, (b) disadvantage of conventional single-chamber cell, (c) and advantages of H-type cell-based electrochemical uranium extraction and synergistic degradation of diglyme.#

Fig.1 Characterization of CuTTB-3. (a) The coordination environment of Cu+. (b) 3D nonporous structure. (c) PXRD patterns treated under various conditions. (d) TGA curve. (e) Cu 2p XPS spectra. (f) Partially magnified Cu K-edge XANES spectra. Color scheme: Cu, orange; C, gray; N, light blue.#

在模拟有机废水电催化提取实验中，如图2所示，CuTTB-3在H型电解池中展现出快速的反应动力学，即便在100 g L⁻¹的高浓度二甘醇二甲醚共存下，阴极铀浓度在1小时内即可实现99.8%的高效去除；阳极二甘醇二甲醚则通过直接电子转移途径被彻底降解为甲酸、二氧化碳与水，总有机碳去除率显著优于单室体系。

Fig.2 Electrochemical uranium extraction kinetics of CuTTB-3 in 100 mg L−1 uranyl with and without diglyme of various concentration (0–50 g L−1) solution under (a) single-chamber cell and (d) H-type cell. Evolution of the ratio of degradation intermediates relative to the initial diglyme concentration over time under (b) single-chamber cell and (e) H-type cell based on 1H NMR. Uranium extraction efficiency under the influence of different degradation intermediates at specific time points (c) under single-chamber cell and (f) H-type cell. (g) The catholyte solution changed from colorless to a yellow suspension in an H-type cell. (h) Comparison of uranium extraction efficiency (solid lines) and residual carbon component content (dashed lines) between H-type (red) and single-chamber (blue) cells over time.#

工艺适应性测试表明，如图3所示，CuTTB-3在pH 1.0至8.0的宽酸碱范围及多种强竞争性共存离子环境中均保持90%以上的提取率。在连续15轮循环测试中，该体系保持了大于96.4%的高效性能，获得了28855 mg g⁻¹的纪录级累积提铀容量与2886 mg g⁻¹ h⁻¹的提取速率。在1升放大流动池装置中，该体系在3 V工作电压下稳定运行，取得了96.8%的单次提取效率与19360 mg g⁻¹的超高处理容量。

Fig.3 The electrochemical uranium extraction efficiency of CuTTB-3 toward the mixture of 100 mg L−1 uranyl and 100 g L−1 diglyme solution in an H-type cell (a) under different pH values, (b) with addition of different sulfates solutions, (c) with addition of different sodium solutions. The error bars represent the standard deviation of parallel measurements. (d) Cyclic uranium extraction performance of CuTTB-3 over 15 cycles in the mixture of 100 mg L−1 uranyl and 100 g L−1 diglyme solution. (e) Comparison of cumulative uranium extraction capacity and cycling stability between this work and state-of-the-art materials. (f) Comparison of the uranium extraction rate and rate with state-of-the-art materials. (g) The flow cell solution changed from colourless to a yellow suspension. (h) Chronoamperometry curve of CuTTB-3 at an applied DC voltage of 3 V.#

对比实验进一步揭示了非多孔结构的决定性优势。如图4所示，同配体构建的多孔类似物CuTTB-4在施加电位仅10分钟后晶体骨架便发生不可逆坍塌并重构为铜纳米颗粒，性能急剧衰退；而CuTTB-3在长期电解后依然保持完好的晶格结构，展现出致密非多孔结构抵御电化学还原失活的独特韧性。

Fig.4 (a) The electrochemical uranium extraction kinetics of CuTTB-3 and CuTTB-4 in uranyl solution with and without 10 g L−1 diglyme solution under a single-chamber cell. (b) The electrochemical uranium extraction kinetics of CuTTB-3 and CuTTB-4 in uranyl solution with and without 10 g L−1 diglyme solution under an H-type cell. The error bars represent the standard deviation of parallel measurements. PXRD patterns of (c) CuTTB-3@carbon paper, (d) CuTTB-4@carbon paper before and after electrocatalysis in uranyl solution with and without 10 g L−1 diglyme. SEM images of (e) CuTTB-3 and (f) CuTTB-4 after uranium extraction.#

结合原位红外、原位拉曼与同步辐射表征，如图5所示，沉积产物确认为水合重铀酸钠晶体，铀在整个过程中稳定保持正六价，证实其遵循析氢反应诱导的局部界面强碱性水解沉淀机制。如图6所示，理论计算与单晶解析表明，尽管多孔CuTTB-4在热力学平衡态下与铀具有更强的吸附亲和力，但非多孔CuTTB-3更低的界面电荷转移阻抗和外加电场驱动动力学完全主导了反应过程，打破了传统“吸附亲和力优先”的选材定势。

Fig. 5 (a) PXRD patterns of uranium deposits collected from single-chamber and H-type cells, compared with reference patterns. (b) TEM elemental mapping images of uranium deposits. (c) U 4f XPS spectra of CuTTB-3 electrode uranium deposits obtained under different electrolytic conditions. (d) U _L_3-edge XANES spectrum of uranium deposits compared with references. (e) Time-dependent in situ ATR-FTIR spectra of CuTTB-3 during electrolysis. (f) Time-dependent in situ Raman spectra of CuTTB-3 during electrolysis.#