Superior Iodine Uptake Capacity Enabled by an Open Metal-Sulfide Framework Composed of Three Types of Active Sites

Open AccessCCS ChemistryRESEARCH ARTICLES22 Jul 2022Superior Iodine Uptake Capacity Enabled by an Open Metal-Sulfide Framework Composed of Three Types of Active Sites Yugang Zhang†, Linwei He†, Tingting Pan†, Jian Xie, Fuqi Wu, Xinglong Dong, Xia Wang, Lixi Chen, Shicheng Gong, Wei Liu, Litao Kang, Junchang Chen, Lanhua Chen, Long Chen, Yu Han and Shuao Wang Yugang Zhang† State Key Laboratory of Radiation Medicine and Protection, School for Radiological and Interdisciplinary Sciences (RAD-X), Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Soochow University, Suzhou 215123 , Linwei He† State Key Laboratory of Radiation Medicine and Protection, School for Radiological and Interdisciplinary Sciences (RAD-X), Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Soochow University, Suzhou 215123 , Tingting Pan† Advanced Membranes and Porous Materials (AMPM) Center, Physical Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900 , Jian Xie School of Life Sciences, School of Civil Engineering, Shaoxing University, Shaoxing 312000 , Fuqi Wu State Key Laboratory of Radiation Medicine and Protection, School for Radiological and Interdisciplinary Sciences (RAD-X), Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Soochow University, Suzhou 215123 , Xinglong Dong Advanced Membranes and Porous Materials (AMPM) Center, Physical Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900 , Xia Wang State Key Laboratory of Radiation Medicine and Protection, School for Radiological and Interdisciplinary Sciences (RAD-X), Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Soochow University, Suzhou 215123 , Lixi Chen State Key Laboratory of Radiation Medicine and Protection, School for Radiological and Interdisciplinary Sciences (RAD-X), Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Soochow University, Suzhou 215123 , Shicheng Gong State Key Laboratory of Radiation Medicine and Protection, School for Radiological and Interdisciplinary Sciences (RAD-X), Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Soochow University, Suzhou 215123 , Wei Liu School of Environmental and Materials Engineering, Yantai University, Yantai 264005 , Litao Kang School of Environmental and Materials Engineering, Yantai University, Yantai 264005 , Junchang Chen State Key Laboratory of Radiation Medicine and Protection, School for Radiological and Interdisciplinary Sciences (RAD-X), Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Soochow University, Suzhou 215123 , Lanhua Chen State Key Laboratory of Radiation Medicine and Protection, School for Radiological and Interdisciplinary Sciences (RAD-X), Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Soochow University, Suzhou 215123 , Long Chen *Corresponding authors: [email protected], E-mail Address: [email protected] E-mail Address: [email protected] State Key Laboratory of Radiation Medicine and Protection, School for Radiological and Interdisciplinary Sciences (RAD-X), Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Soochow University, Suzhou 215123 , Yu Han *Corresponding authors: [email protected], E-mail Address: [email protected] E-mail Address: [email protected] Advanced Membranes and Porous Materials (AMPM) Center, Physical Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900 and Shuao Wang *Corresponding authors: [email protected], E-mail Address: [email protected] E-mail Address: [email protected] State Key Laboratory of Radiation Medicine and Protection, School for Radiological and Interdisciplinary Sciences (RAD-X), Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Soochow University, Suzhou 215123 https://doi.org/10.31635/ccschem.022.202201966 SectionsSupplemental MaterialAboutAbstractPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InEmail Efficient adsorption of gaseous radioiodine is pivotal for the sustainable development of nuclear energy and the long-term radiation safety of the ecological system. However, state-of-the-art adsorbents (e.g. metal–organic frameworks and covalent–organic frameworks) currently under exploration suffer severely from limited adsorption capacity, especially under a real-world scenario with extremely low radioiodine concentration and elevated temperature. This mostly originates from the relatively weak sorption driving forces mainly determined by the iodine-adsorbent interaction consisting of noncovalent interactions with a small fraction of strong chemical bonding. Here, we document the discovery of an open metal-sulfide framework ((NH4)2(Sn3S7), donated as SCU-SnS) constructed by three different types of active sites as a superior iodine adsorbent. Benefiting from the ability of iodine for pre-enrichment into the framework by charge-balancing NH4+ through N–H···I interaction, the efficient reduction of I2 affording I− by S2−, and extremely high binding affinity between Sn4+ and I−, SCU-SnS exhibit a record-breaking iodine adsorption capacity (2.12 g/g) under dynamic breakthrough conditions and the highest static capacity (6.12 g/g) among all reported inorganic adsorbents, both at 348 K. Its facile synthesis and low cost endow SCU-SnS with powerful application potential for the nuclear industry. Download figure Download PowerPoint Introduction Efficient removal of radioiodine during nuclear reactor operation, used nuclear fuel (UNF) reprocessing, and nuclear accidents is significant for the sustainable development of the nuclear industry and the physical health of the general public.1 However, how to efficiently capture the extremely low molar concentration of diatomic radioiodine under harsh conditions with elevated temperature and high humidity2,3 in real-world off-gas streams (I2, 90%∼100%; organic iodine, 0%∼10%) remains an unresolved issue. Apart from the traditional wet scrubbing method, solid-phase adsorption is another practicable approach to eliminate radioiodine in reprocessing plants with the merit of generating negligible liquid waste. To date, an increasing number of solid-state adsorbents have been investigated for their potential iodine removal performance. Activated carbon (AC) has been used extensively in iodine traps from benign gaseous streams even though it is not suitable for handling the off-gas in UNF reprocessing plants in light of its poor adsorption affinity and low ignition point.4 Although metal–organic frameworks (MOFs)5–9 and covalent–organic frameworks (COFs),10,11 both cutting-edge classes of porous materials, exhibit excellent static adsorption capacities for iodine, their relatively high cost and moderate stability under harsh reprocessing conditions (e.g., with acids) severely limit their practical applications.12–15 More importantly, their capture capability mainly relies on physical adsorption and/or noncovalent interactions, which leads to undesirable removal properties for low-concentration iodine at high temperatures. Silver-immersed or silver-exchanged zeolites are the commercially utilized adsorbents in the nuclear industry, benefiting from the well-known reaction affinity of silver with iodine.16,17 However, the limited capacity and availability of silver gives rise to the modest iodine removal performance that is critically in need of improvement. Furthermore, the extensive use of silver gives rise to high costs accompanied by inevitable environmental pollution. Therefore, it is crucial to seek more efficient and economic adsorbents for removing radioiodine under dynamic conditions. Chalcogen-based aerogels (chalcogels) are promising radioiodine getters due to their low cost combined with a strong affinity of sulfur for iodine.18–22 However, limited by their randomly and broadly distributed nanoscale pores and arbitrarily arranged sulfur atoms, these chalcogels exhibit slow adsorption kinetics, weak interaction efficiency, and scant adsorption capacity. In addition, the complex and time-consuming synthesis process of aerogels restricts their widespread application. As the crystalline analogues of chalcogels, metal sulfides,23–29 with their versatile composition and perforated frameworks, are considered as iodine scavenger candidates. The precisely configured and exposed coordination atoms in crystalline metal sulfides provide approachable binding sites for iodine adsorption. Furthermore, the inherent pore structure offers an accessible diffusion path for gaseous iodine, potentially leading to enhanced adsorption kinetics. Herein, we rationally designed and prepared a microporous two-dimensional thiostannate ((NH4)2(Sn3S7), donated as SCU-SnS) containing charge-balancing NH4+ with high surface polarizability for iodine removal. First, given their structure and components, abundant hydrogen atoms originating from NH4+ can pre-enrich I2 via strong hydrogen-bond interaction (N–H⋯I).30,31 Second, the soft Lewis base S2− can capture I2 by its strong interaction with soft Lewis acid I2 coupled with its reduction propensity towards I2 affording I−.32 Third, Sn4+ has been demonstrated to be an excellent I2 getter with a much higher preference for iodization reaction than Ag+ in terms of Gibb's free energy.33 As expected, integration of these three different active sites into a single porous material gives rise to a record-breaking iodine uptake amount under dynamic conditions at 348 K. In addition, SCU-SnS displays the highest static iodine adsorption capacity at 348 K among all reported inorganic materials. The idea of materials entirely composed of well-arranged active sites inspires a new design strategy for constructing efficient adsorbents. Experimental Methods and Characterization Synthesis of SCU-SnS The mixture of tin powder (357 mg, 3 mmol), sulfur (224 mg, 7 mmol), and diethylenetriamine (2.5 mL) was added into a 20 mL stainless steel polytetrafluoroethylene vial. The vial was heated to 180 °C for 4 days, and then it was cooled to room temperature at a rate of 6 °C/h. Yellow block crystals and black substances were obtained. After the density variation with bromoform, we purified the product and finally acquired the yellow crystals of SCU-SnS. Results and Discussion Structure and stability characterizations The solvothermal reaction of tin and sulfur powders in the presence of diethylenetriamine affords pure yellow block crystals with a high yield of 68.4%. Singl-crystal X-ray diffraction analysis reveals that it crystallizes in a centrosymmetric space group P63/mmc ( Supporting Information Table S1). The asymmetric unit of SCU-SnS contains two crystallographically distinct Sn4+ ions, six S2− ions, and two ammonium cations. All Sn atoms coordinate with five diverse S atoms, forming SnS5 trigonal bipyramids ( Supporting Information Figure S1a), which further connect to generate Sn3S10 polyhedrons ( Supporting Information Figure S1b). The Sn3S10 core further integrates by edge sharing, to form a 2D [Sn3S7]n2n− anionic layer parallel to the [001] plane. The 2D [Sn3S7]n2n− layers are stacked in the AA sequence along the c axis (Figure 1b). The interlayer distance is measured to be 5.876 Å. Originating from the thermal decomposition of diethylenetriamine, the NH4+ cations as counterions can be identified in the interlayer space and form N–H⋯S hydrogen bonds with the sulfur atoms on the [Sn3S7]n2n− layers (Figure 1a). SCU-SnS features a two-dimensional network containing 12 × 12 Å2 channels (Figure 1c), similar to reported tin sulfides Fujian Institute of Research on the Structure of Matter (FJSM)-SnS,24 Cs-SnS-1,34 and TMA-SnS-1 (TMA = tetramethylammonium).35 The solvent molecules of diethylenetriamine are highly disordered in these channels, whose amounts can be determined by taking into consideration the results of crystallographic data, element analysis ( Supporting Information Table S2), and thermogravimetric analysis (TGA, Supporting Information Figure S3). Figure 1 | The adsorption strategies and corresponding deficiencies of (i) chalcogen-based aerogels and (ii) silver-exchanged zeolites. (iii) The structure and active sites of SCU-SnS: (a) the secondary structure unit of SCU-SnS; (b) view of the 2D [Sn3S7]n2n− anionic layer along the ac plane; (c) view of the 2D [Sn3S7]n2n− anionic layer with large windows parallel to the ab plane. S = orange; Sn = indigo blue. All nitrogen and hydrogen atoms have been omitted for clarity. Download figure Download PowerPoint The consistency between the experimental and the simulated powder X-ray diffraction (PXRD) patterns indicates the high phase purity of SCU-SnS ( Supporting Information Figure S2). As shown in the scanning electron microscopy (SEM) image in Supporting Information Figure S4, the micromorphology of SCU-SnS is a lamellar structure in accordance with its crystal structural topology. In the energy-dispersive X-ray spectroscopy (EDS) spectrum, the chemical composition results show that the molar ratio of Sn∶S is 3.09∶6.86, consistent with the crystallographic results. Moreover, the characteristic peak located at nearly 0.4 keV demonstrates the abundant presence of that N element originating from NH4+ and diethylenetriamine in this structure ( Supporting Information Figure S4).36 To further study the thermal stability of SCU-SnS, TGA was performed ranging from 30 to 900 °C under a nitrogen atmosphere. An approximately 1.97% weight loss before 100 °C resulted from the loss of surface water molecules. The second 31.56% weight loss indicated the decomposition of the structural framework and volatilization of diethylenetriamine (b.p. 206 °C) when the temperature increased higher than ca. 400 °C. Then the sample gradually transformed into analogues of SnS with the increasing temperature.24 The hydrolytic stability of SCU-SnS was also tested by soaking the crystal in aqueous solutions with different pH values. Supporting Information Figure S5 shows that SCU-SnS can maintain its crystallinity in aqueous solutions over a wide pH ranging from 3 to 11. Intriguingly, SCU-SnS maintains its original crystallinity even after treatment with 200 kGy γ or β irradiations ( Supporting Information Figure S6). The high thermal, hydrolytic, and irradiation stability suggests that SCU-SnS is an excellent absorption material for radioactive iodine under harsh conditions (e.g., elevated temperature, high moisture, and an intensive radiation field). Static sorption efficiency for I2 vapor Considering the robust framework and densely exposed active sites (S2− and Sn4+), the sorption performance of SCU-SnS toward I2 vapor was first investigated in a static closed system (the saturated vapor pressure of iodine is 1.6 kPa, which corresponds to a volumetric concentration of 1.6 × 104 ppm bar according to the National Institute of Standards and Technology empirical formula).37,38 The iodine capture property was measured at 348 K under ambient pressure to evaluate its adsorption capacity by recording the sample weight as a function of time. Remarkably, SCU-SnS rapidly adsorbed 401 wt % of the I2 molecules within 18 h and reached a maximum uptake amount of 612 wt % by 120 h (Figure 2a). Even though this static saturated adsorption capacity is below that of some COFs (iCOF-OH-AB, JUC-561)39,40 and porous organic polymers (POPs) ([email protected], TBIM [T = 2,4,6-trichloro-1,3,5-triazine, BIM = biimidazole])41–45 with respect to their low density, high surface area, and nitrogen-rich structure, this capacity is significantly higher than those of all reported inorganic materials ( Supporting Information Table S4), the vast majority of MOF materials46–48 (MOF-808, CuBTC, ZIF-8), and functionalized active carbon49 (KOH-AC) under the same conditions. In addition, this adsorption capacity of SCU-SnS is also evidently superior to that of all chalcogen-based aerogels with higher Brunauer–Emmett–Teller surface areas. Therefore, the synergistic effect of abundantly exposed S2− and Sn4+ sites in the perforated layers, as well as the NH4+ in the pores, dramatically improves its sorption capability for the I2 molecule. The chemical adsorption is also confirmed by the well-fitted pseudo-second-order model ( Supporting Information Figure S7 and Table S3). Moreover, the retention experiments were conducted by exposing I2-loaded SCU-SnS (denoted as I2@SCU-SnS) samples to air at room temperature and ambient pressure to verify the major interaction type between SCU-SnS and iodine molecules. I2@SCU-SnS maintains its mass for at least 6 days ( Supporting Information Figure S8), indicating that the high adsorption capability is derived from the strong affinity between SCU-SnS and the iodine molecule instead of the surface physical interaction. More intriguingly, when SCU-SnS is exposed to high doses of 60Co γ-irradiation and β-irradiation (provided by an electron accelerator), its saturated adsorption capacity is nearly unchanged under the same adsorption conditions (Figure 2b). Figure 2 | (a) Static adsorption performance of iodine by SCU-SnS at 348 K. (b) The β-irradiation and γ-irradiation resistance of SCU-SnS evaluated by I2 uptake capacities. (c) The breakthrough curves of I2 for SCU-SnS at 298 (blue dots) and 348 K (red dots). (d) Bar graphs of the dynamically captured amounts of I2 by SCU-SnS at 298 and 348 K under dry or humid conditions. (e) The comparison of saturated iodine uptake capacities in static and dynamic conditions for various reported materials (note: the iodine vapor uptakes for MIL-101-Cr-TED and MIL-101-Cr-HMTA are under the condition of 150 ppm of I2). Download figure Download PowerPoint Breakthrough studies for I2 vapor To probe potential practical applications, the dynamic adsorption experiment was carried out under simulated nuclear fuel reprocessing conditions via a fixed-bed column breakthrough setup, in which I2 vapor was carried by N2 (flow rate: 10 mL/min at 1 bar; I2 concentration: 400 ppm) to pass through a sorbent bed packed with 70 mg of the adsorbent. The temperature of the adsorbent bed was set to 298 or 348 K. The dynamic I2 adsorption capacity of SCU-SnS was determined by inductively coupled plasma-mass spectrometry. For the breakthrough experiment at 298 K, I2 vapor was initially detected in the effluent at 30 h, after which its concentration plateaued until a complete breakthrough was achieved after 120 h (Figure 2c). Discrepant adsorption behavior was observed for SCU-SnS at 348 K. Very significantly, the breakthrough time at 348 K takes much longer, approaching 100 h, more than 10 times that of some recently reported COF materials.37,39 According to its mass increment, the total I2 uptake of SCU-SnS was determined to be 166 wt % at 298 K and 212 wt % at 348 K under dynamic breakthrough conditions. It should be noted that the adsorption capacity of SCU-SnS at 298 K is significantly higher than that of all inorganic adsorbents, such as HISL (53 wt %, HISL = hydrophobicity-intensified silicalite-1)4 and Ag0@MOR38 (8 wt %), and is only lower than those of iCOF-AB-50 (279 wt %) and COF-OH-50 (170 wt %)39 ( Supporting Information Table S5). Note that these porous materials have excellent adsorption capacity for I2 only at 298 K, which is mainly attributed to their high porosity and abundant sorption sites contributed to by weak noncovalent interaction. However, the channel effect for capturing I2 was rapidly weakened as the temperature increases, owing to the thermal activation of I2. This phenomenon was confirmed by the greatly decreased adsorption capacities of these materials at the elevated temperature of 348 K.37,39 On the contrary, increasing the temperature remarkably enhanced the dynamic adsorption amount of SCU-SnS, also contrasting sharply with the case of Ag0@MOR with exothermal sorption reaction only.50 In fact, to the best of our knowledge, the uptake amount of 212 wt % is a new record value at 348 K, distinctly superior to COF materials (Figure 2e, Supporting Information Table S6). The above exceptional capacity can be rationalized by the following. On the one hand, the reaction between S2− and I2 molecules is an endothermal process,51 which promotes the transformation of I2 to I− at higher temperatures. On the other hand, the elevated temperature accelerates the reaction rate of the formation of SnI4.33 According to the molar weight of Sn4+, the maximum theoretical adsorption capacity of SCU-SnS is 200 wt %, which is very close to the actual adsorption quantity of 212 wt %. Since the dissolved off-gas from nuclear fuel reprocessing also contains a certain extent of water vapor, the I2 capture performance of SCU-SnS was investigated under humid conditions (RH = 50%) at 298 and 348 K, respectively. SCU-SnS adsorbed 155.8 wt % iodine at 298 K and 164.2% iodine at 348 K as the iodine completely breaks through, representing a slight decrease compared to that in dry conditions (Figure 2d). Despite the high affinity among SCU-SnS and water molecules determined by the contact angle measurement ( Supporting Information Figure S9), SCU-SnS still displays an excellent capability for capturing I2 molecules. These results illustrate that SCU-SnS is probably the most promising candidate as a packing column sorbent material for I2 uptake reported to date and further affirms that forming highly stable chemical bonds among adsorbents and I2 molecules is a feasible way to remove I2 molecules under the coupled conditions of high temperature and increased humidity. In terms of the dynamic adsorption capacity of SCU-SnS, the capture cost for SCU-SnS was estimated and compared to that of Ag0@MOR. As shown in Supporting Information Table S7, for one round of adsorption, the cost of SCU-SnS is almost 300 times lower than that of Ag0@MOR, representing a significant savings for removing an equal quantity of I2 molecules. Of note, although the silver-containing zeolite can be partially reused, the adsorption capacity is dramatically reduced due to the oxidation of active silver and its migration to the inner zeolite networks.16,17 In addition, the regeneration process presents a tough issue because released radioiodine can contaminate the related equipment. Instead, the irreversible nature of the sorption reaction between SCU-SnS and I2 coupled with its low cost and the simple and scalable synthesis of SCU-SnS suggests the possibility of direct disposal of the I2-incorporated material after the sorption process as a stable waste form of radioiodine. Investigation of adsorption mechanism for I2 The outstanding adsorption capacity of SCU-SnS towards I2 encouraged us to further investigate its interaction mechanisms. As shown in Supporting Information Figure S10, the iodine-saturated captured product I2@SCU-SnS changes to pristine morphology, and its color turns black, similar to that of I2. Elemental mapping images using SEM-EDS show the homogenous distribution of I in I2@SCU-SnS compared with SCU-SnS ( Supporting Information Figure S11). Furthermore, the iodine species and adsorption reaction were determined via the comprehensive analysis of PXRD, Raman (RM), and Fourier transform infrared (FT-IR) results. The PXRD pattern of pristine I2@SCU-SnS exhibits intense peaks assigned to crystalline SnI4 (Figure 3b). In addition, the generation of SnI4 was also visually confirmed by the newly formed orange solid adhering to the dynamic adsorption columns ( Supporting Information Figures S12 and S13). As the Raman spectrum of I2@SCU-SnS shows in Figure 3a, the band at 109 cm−1 is ascribed to the characteristic peak of I3−, which is quite different from the vibrational overtones of molecular iodine at 183 cm−1.52,53 This result indicates that charge transfer interactions occurred between SCU-SnS and iodine. Significantly, the additional peak located at 218 cm−1 is attributed to symmetric and asymmetric S–S vibrations.54 According to the FT-IR spectra ( Supporting Information Figure S14), there are no clearly observable SO42− bands at approximately 1097 cm−1.32 Taking the Raman and FT-IR results into consideration, elemental sulfur (S8) is the most likely oxidation product other than SO42−. Thus, the possible schemes for the reaction between I2 and SCU-SnS can be described as follows: (NH4)2Sn3S7 + I2 → NH4[I−•I2] + SnI4 + S8. The polyiodide anions I3− form between adsorbed I2 and I−. Figure 3 | (a) The Raman spectra of SCU-SnS and I2@SCU-SnS. (b) The PXRD patterns of SCU-SnS, I2@SCU-SnS, and SnI4. (c) The I 3d XPS spectrum of I2@SCU-SnS. (d) The N 1s XPS spectra of SCU-SnS and I2@SCU-SnS. (e) The schematic diagram of the adsorption of iodine by SCU-SnS. S = orange; Sn = indigo blue; N = bluish violet. All hydrogen atoms have been omitted for clarity. Download figure Download PowerPoint X-ray photoelectron spectroscopy (XPS) measurements were carried out to further explore the chemical species of iodine and the host-guest interactions between SCU-SnS and iodine ( Supporting Information Figure S15). As shown in Figure 3c, the adsorbed iodine was verified by the two characteristic peaks of I 3d with the binding energies ranging from 630 to 610 eV. Actually, the peaks at 628.95 and 617.45 eV from I2@SCU-SnS typically are assigned to I 3d3/2 and I 3d5/2, indicating that I3− is the only iodine species adsorbed on the sample.55 This result demonstrates that chemisorption accounts for the high uptake performance under harsh conditions. In addition, a remarkably new N 1s peak fraction at 400.4 eV was observed, confirming the host–guest interaction between I3− and NH4+ (Figure 3d).39 Based on the adsorption mechanisms of I2@SCU-SnS, the overall I2 adsorption process can be inferred as follows. First, the I2 molecules pervade the open channels through molecular diffusion. An increasing number of I2 molecules are captured in the perforated frameworks by the physical adsorption and "soft-soft" interaction between S2− and I2. Further, I2 molecules oxidize S2− resulting in the formation of S8 and I−. Meanwhile, the NH4+ in the channels physically adsorbs newly produced I3− through electrostatic attraction and the hydrogen bond. As the reaction continuously progresses, the Sn4+ sites are exposed and combined with I− to generate SnI4. As the temperature increases, the reaction is promoted so that more I2 molecules are adsorbed by SCU-SnS (Figure 3e). Therefore, this adsorption process provides a fundamental design principle and new route for the creation of promising adsorbents with high metal content and accessible active sites leading to excellent adsorption affinity towards I2 molecules under complex conditions. Conclusion In this contribution, we present a new design philosophy for high-performance I2 adsorbents via an open metal-sulfide framework SCU-SnS that can be facilely synthesized by a one-pot solvothermal method with high yields. Coupled with the strong reduction capability of S2− and high reaction affinity of Sn4+ for iodine, SCU-SnS possesses a record-breaking dynamic adsorption capacity (2.12 g/g) for low iodine concentration (400 ppm) at 348 K. In addition, the static capacity (6.12 g/g) at 348 K far surpasses all reported inorganic adsorbents. Importantly, its low cost is a promising advantage compared with other adsorbents, such as MOFs, COFs, and Ag0@MOR. The chemical adsorption mechanism was confirmed by the comprehensive analysis of experimental PXRD, Raman, and XPS results, in which the synergetic redox and complexation reactions give rise to the formation of sulfur and SnI4. Based on the above multiple-cooperative adsorption mechanisms that anchor various active reaction sites in porous frameworks, SCU-SnS, with its merits of superior adsorption performance and ultralow cost, provides a new model to design efficient adsorbents for in-depth removal of various types of environmental pollutants. Supporting Information Supporting Information is available and includes additional experiments, Figures S1–S15, and Tables S1–S7. Conflict of Interest The authors declare the following competing financial interest: a patent application for iodine removal material has been filed by inventors Shuao Wang, Yugang Zhang, Linwei He, Long Chen, and Lanhua Chen. Acknowledgments The authors grat