【Angew.Chem.】105℃下的“点石成金”：光热一维共价有机框架实现3489 mg/g的超高容量黄金回收
文章标题：Leveraging Photothermal Effect in 1D Covalent Organic Frameworks for Efficient, Rapid, and Selective Gold Recovery
通讯作者：Zhiyong Li, Yawei Liu, Jianji Wang
文章概要
引言
电子垃圾的剧增带来了严峻的环境挑战，但其中蕴含的贵金属也使其成为一座巨大的“城市矿山”。从电子垃圾浸出液中回收黄金，不仅能缓解资源紧缺，更是绿色可持续发展的必然选择。然而，传统的工业回收方法存在能耗高、选择性低以及二次污染严重等弊端。近年来，共价有机框架（COF）因其高比表面积和结构可调性在黄金回收领域展现出潜力。然而，现有的二维或三维COF往往面临活性位点暴露不足、传质阻力大以及在复杂多金属体系中动力学迟缓等瓶颈。如何同时构建具有高吸附容量、极速动力学和优异选择性的先进吸附材料，依然是资源循环利用领域的重大挑战。
Structure and synthetic routes of TN-COF and TC-COF.
主要实验及结论
研究人员通过非线性单体与多功能分子的席夫碱缩合反应，成功设计并合成了两种具有一维周期性条带状拓扑结构的光热功能材料TN-COF和TC-COF。通过粉末X射线衍射和理论模拟结构精修，证实了其高度结晶的一维AA堆叠骨架，这种独特的“核壳”状开放通道最大程度地暴露了活性位点并赋予材料极佳的化学稳定性。紫外-可见漫反射光谱和Mott-Schottky测试表明，由于分子内强偶极相互作用与延展的共轭体系，两种材料具备覆盖全可见光至近红外区的宽谱光吸收特性，其导带底电位均负于金离子的标准还原电位。更重要的是，材料表现出极强的非辐射跃迁特性，在可见光照射下局部温度可在短短一分钟内飙升至105°C，展现出卓越的光热转换效率，这为打破传统放热吸附的限制、通过热效应驱动吸附平衡右移奠定了坚实的基础。
PXRD patterns of TN-COF (a) and TC-COF (b) with Pawley refinement; (c) Theoretically unit cells of the AA stacking modes for TN-COF; (d) FT-IR spectra of TPAD-NH2, Pyd, IPA, TN-COF and TC-COF; (e) and (f) N2 sorption isotherms at 77 K and pore size distribution (insert) of TN-COF and TC-COF.
(a) UV/vis DRS plot of TN-COF and TC-COF; Mott–Schottky plots of TN-COF (b) and TC-COF (c); (d) The band structure diagram of TN-COF, TC-COF and the standard reduction potentials of AuCl4−; (e) Transient photocurrent response curves of TN-COF and TC-COF; (f) Electron spin resonance spectra of TN-COF at room temperature; (g) Temperature changes of TN-COF and TC-COF under different light intensities (red line for TN-COF, green line for TC-COF); (h) Photothermal images of TN-COF before and after 300 mW/cm2 illuminations.
在吸附性能测试中，TN-COF在可见光照射下的最大吸附容量达到了惊人的3489 mg/g，相比于无光照条件提升了1.4倍，高居目前已报道的COF类吸附剂前列。动力学实验表明，在100 ppm的金离子溶液中，两种材料在短短20秒内即可移除超过99%的金离子。在面对高浓度干扰离子共存的超复杂体系时，TN-COF表现出对金的绝对优先亲和力，选择性系数超越了两万。当直接应用于真实的高酸性电子垃圾——废弃CPU王水浸出液时，即使金离子浓度仅有17 ppm且伴随数千倍的铜和镍干扰，TN-COF仍实现了高达99%的黄金精准回收。机制分析表明，吸附过程协同了多 field 耦合效应，多氮氧位点首先通过静电和配位作用高效捕获金离子，随后材料的光生电子与质子化氨基将金还原为零价金属颗粒，而光热效应引起的界面局域高温则进一步加速了这一吸热的化学还原过程，从而实现了协同促升。
(a) The effect of pH values on the AuCl4− adsorption by TN-COF and TC-COF; Adsorption isotherms of TN-COF (b) and TC-COF (c) for AuCl4− with different concentrations under ambient and visible light irradiation, qe, equilibrium adsorption capacity: 5 mg of COF, 10 mL of AuCl4− solution, t = 6 h; Kinetic adsorption of AuCl4− on TN-COF and TC-COF under ambient and visible light irradiation for c0 = 100 mg L−1 (d) and 1000 mg L−1 (e); (f) Au(III) removal efficiency of TN-COF and TC-COF in the presence of various interfering metal ions (t = 2 h).
(a) The AuCl4− (1000 ppm) removal efficiency of TN-COF and TC-COF over 25 cycles; (b) Comparison of gold capacity among TN-COF, TC-COF and reported representative COFs (TPDA-DPTA-COF [22], N+-PYTA-PATA-COF [40], Ionic-COF-Cl [41], TTF-COF [32], PYTA-PZDH-COF [44], COF-TPTD-DHTA-TAB [46], PP-COF [21], COF-HNU25 [5], JUN-1 [42], TpTsc [43], NKCOF-77 [15], TpDa-COF [16], TzDa-COF [45]); (c) Au(III) adsorption of TN-COF and TC-COF from the disposed Intel CPU leaching solution; (d) SEM images and EDS mapping of metal spin from the Intel CPU; (e) Au(III) adsorption capacity and removal efficiency by TN-COF and TC-COF in the outdoor environment of the Henan Normal University (HNU) campus from 11:17 am to 15:17 pm July 05, 2025 (sunny, 31°C, c0 = 1000 ppm), the location is east longitude 113°54′46“ and north longitude 35°19′46”.
(a) PXRD patterns of TN-COF after the Au(III) recovery under ambient and visible light irradiation; (b) SEM mapping images of TN-COF after Au(III) adsorption; (c) XPS profiles of TN-COF before and after Au(III) adsorption; High-resolution XPS spectrum of Au 4f (d), N 1s (e) and O 1s (f) after Au(III) adsorption under ambient or visible light irradiation.
(a) Electronic localization function (ELF) mapping and (b) Electrostatic potential (ESP) for TN-COF. The fs-TAS spectra at 405 nm excitation, transient absorption spectra at selected delay times and kinetic trace with Dec2-exponential fitting for TN-COF (c–e); (f) The schematic illustration for the adsorption mechanism of gold by TN-COF.
总结及展望
该工作成功将兼具高效光热效应与丰富多齿配位位点的功能单体引入一维共价有机框架中，开创性地提出了一种光热效应协同光化学还原驱动黄金超快回收的新策略。该材料不仅在模拟废液中展现出令人瞩目的吸附容量与秒级极速，更在真实电子垃圾的资源化利用中印证了其巨大的工业应用前景。此外，使用绿色温和的草酸与硫脲混合液作为洗脱剂，材料在历经25次循环吸附-脱附后仍保持初始性能的96%以上，结构未见破坏，证明了极高的可重复使用性。这种多场耦合增强的吸附机制，为未来针对特定工业战略金属回收而设计开发下一代高稳定性、高智能化的功能性有机多孔材料提供了全新且极具参考价值的微观构筑范式。