CO2在氨基改性MIL-101(Cr)中吸附的分子模拟

采用实验与分子模拟结合的方法研究298 K下CO_2在氨基改性得到的MIL-101(Cr)-NH_2和MIL-101(Cr)-ED(ED:乙二胺)上的吸附性能。比较MIL-101(Cr)、MIL-101(Cr)-NH_2和MIL-101(Cr)-ED的吸附等温线与吸附热的结果,表明采用直接合成改性法得到的MIL-101(Cr)-NH_2比采用合成后再改性得到的MIL-101(Cr)-ED有更高的CO_2吸附容量。进一步比较密度分布图和径向密度分布曲线,分析CO_2在氨基改性MIL-101(Cr)中的吸附位,表明在低压下CO_2首先吸附在MIL-101(Cr)微孔的超级四面体中,随着吸附压力的增大逐渐填充到更大的孔中。氨基的存在增加了CO_2的吸附位点,使MIL-101(Cr)-NH_2具有较高CO_2吸附容量;同时MIL-101(Cr)-ED中的ED分子的存在增加了CO_2的吸附位点,使MIL-101(Cr)-ED也具有较高CO_2吸附容量;但是MIL-101(Cr)-ED中的ED分子占据了MIL-101(Cr)中Cr的吸附位点,使Cr对CO_2的吸附强度减弱,同时可吸附位点少于MIL-101(Cr)-NH_2,导致其对CO_2的吸附容量少于MIL-101(Cr)-NH_2。     

乙二胺改性轻金属铝-金属有机骨架材料用于CO2/CH4分离

胺类分子在CO₂的捕获中可以起到选择性提升的作用,本文选择小尺寸的乙二胺分子对具有不饱和金属位点的轻金属铝基金属有机骨架（Al-MOFs）材料MIL-100Al进行改性,利用XRD、N₂吸附和FT-IR等对改性材料的结构进行表征,测试了不同浓度的乙二胺改性的MIL-100Al对CO₂和CH₄吸附性能。结果表明,与原始的MIL-100Al材料相比,改性后的材料对CO₂吸附量有明显提高,CH₄的吸附量却降低,从而进一步提高了材料的CO₂/CH₄吸附选择性,提升了吸附分离的效果。     

金属有机框架材料对[Fe(HB(pz)3)2]自旋转换行为的影响

通过在介孔结构金属有机框架材料MIL-101（Cr）和MIL-100（Al）的孔洞中合成自旋交叉化合物[Fe（HB（pz）₃）₂]的方法,可以得到SCO@MOF复合物。通过红外光谱（FTIR）、粉末X射线衍射（PXRD）、原子吸收光谱（AAS）以及气体吸附-脱附等进行了进一步测试。通过变温磁测量对复合材料的温度诱导自旋转换行为的研究表明,复合材料的自旋转换行为发生改变甚至是消失了。复合材料的这一现象可以解释为[Fe（HB（pz）₃）₂]在MOF主体材料的孔洞中形成了一种新的结晶相,且孔壁压力将会阻碍[Fe（HB（pz）₃）₂]从低自旋态向高自旋态转变。不同SCO@MOF复合物得到了相似的自旋转换行为结果。这确认了当自旋交叉化合物在金属有机框架材料孔洞中形成时,MOFs材料的限制压力或基体效应对其自旋转换行为的影响显然是至关重要的。     

MIL-101/P25复合材料的制备及光催化性能

本文采用水热法,将MIL-101负载到预处理过的P25表面,制得MIL-101/P25复合光催化材料,通过X射线衍射（XRD）、傅里叶变换红外（FTIR）、低温N₂物理吸附-脱附（BET）、热重（TG）、场发射透射电镜（FETEM）和光致发光光谱（PL）等对催化剂进行结构表征,同时考察MIL-101及复合材料的稳定性,并且提出协同因子指标来定量评价复合带来的协同效应。结果表明MIL-101呈片状,与P₂₅部分结合。复合后,MIL-101的稳定性得到提高。在适当的配比下,复合具有协同效应,当Cr（NO₃）₃·9H₂O与P25的物质的量之比为1：1时,复合材料对罗丹明B的可见光催化活性最高,协同因子达到1.64。复合材料对无色有机污染物水杨酸同样表现出良好的光催化效果。     

单原子Ge助剂修饰Cu(111)晶面上CO2加氢制甲醇的机理研究

针对CO₂热催化转化制甲醇过程中CO₂吸附、活化较困难及副产物较多的问题,提出采用单原子Ge助剂修饰Cu(111)晶面的解决思路,通过密度泛函理论(DFT)计算研究了CO₂在Ge-Cu(111)晶面上加氢合成甲醇的反应机理。结果表明,单原子Ge助剂的电子调控增加了与其相邻的 Cu 原子的电子云密度,使 CO₂分子在含 Ge 活性界面上的吸附能力显著增强:CO₂在 Ge-Cu(111)晶面上的吸附能约为Cu(111)晶面的1.5倍,约为Pd改性Cu(111)晶面的2.4倍,进而使逆水煤气变换(RWGS)反应路径速控步骤的活化能降低了近 20 kJ·mol^-1,同时衍生出 3条生成甲醇的 RWGS新路径;此外,Ge-Cu(111)晶面上甲酸盐路径由于速控步骤活化能大幅上升而被禁阻,进而CO及烃类等副产物选择性大幅降低,Ge-Cu(111)晶面上CO₂加氢制甲醇选择性升高。     

氨基化修饰介孔Fe3O4@SiO2@mSiO2磁性核壳复合微球的可控制备及吸附性能

以水热法制备的高磁饱和强度Fe₃O₄纳米颗粒为核,正硅酸乙酯（TEOS）为前驱体,采用改进的Stöber法,制备介孔SiO₂包覆Fe₃O₄磁性核壳复合微球。利用XRD、SEM、TEM、N₂吸-脱附、FTIR和VSM对制备样品的物相结构、形貌和磁性能进行了测试表征。研究结果表明,制备的复合材料呈球形,粒径分布均一,材料的比表面积和磁饱和强度分别为413 m²·g^-1和68.93 emu·g^-1。研究了TEOS的添加量对复合微球形貌的影响,随着TEOS添加量的增加,SiO₂壳层增厚,复合粒子形貌均匀,饱和磁化强度有所下降,仍具有良好的超顺磁性。在此基础上,通过接枝法在复合微球的表面接枝-NH₂,制备了一种新型磁性纳米吸附剂（Fe₃O₄@SiO₂@mSiO₂-NH₂）,进而研究了其对水中重金属离子Cr（Ⅳ）的吸附性能。通过动力学拟合,Fe₃O₄@SiO₂@mSiO₂-NH₂对Cr（Ⅳ）的吸附过程是准二级动力学模型占主导地位。探究了该材料对Cr（Ⅳ）的吸附过程和吸附机理。结果表明,其吸附机理及吸附容量与Cr（Ⅳ）的离子形态及-NH₂有关,并通过吸附剂与吸附质之间的电子共用或静电吸附实现。     

傅立叶变换红外光谱技术在超临界CO2作用聚合物体系中的应用

超临界CO₂（scCO₂）作为一种物理化学性质优良、具有高扩散速率及优良溶解性能的溶剂,在科学研究及工业生产中广受青睐。将scCO₂应用于聚合物体系中,CO₂ 与聚合物间特殊的相互作用有利于CO₂分子在聚合物中的吸附与扩散。同时通过CO₂的吸附及其对聚合物的溶胀和塑化作用,聚合物所处微观化学环境以及整体结构性质会发生一定的变化。由于傅立叶变换红外光谱（FTIR）技术能够有效地考察化学环境变化对分子结构造成的影响,这一表征技术在超临界CO₂作用体系中广为应用。本文主要选取了近年来利用FTIR技术考察scCO₂作用于聚合物体系的一些实例,从CO₂-聚合物相互作用机理,scCO₂对聚合物或生物大分子的加工过程的影响两方面,阐述了利用红外光谱技术在scCO₂作用体系中的应用以及前景。     

密度泛函理论研究NO在CuCr2O4(100)表面的吸附

运用密度泛函理论研究了NO在CuCr₂O₄(100)表面4个可能吸附位的顶位吸附。结果表明:表面铜(Cu)和铬(Cr)为活性吸附位，吸附能分别为98.1 kJ·mol^-1和92.9 kJ·mol^-1。对活性吸附位Cu位和Cr位考虑了NO以N端和O端2种吸附取向的吸附，发现N端吸附比O端吸附更为有利，O端吸附为简单的物理吸附。在2种吸附取向情况下，N-O键的伸缩振动频率都发生了红移。Mulliken布居分析表明，N端吸附时NO分子失去电子;对NO吸附前后的态密度分析可知，对Cu位和Cr位N端吸附NO的2π轨道得到电子。本文并进一步讨论了NO分子在CuCr₂O₄ (100)表面Cu位和Cr位的成键机理。     

单原子Ge助剂修饰Cu(111)晶面上CO2加氢制甲醇的机理研究

针对CO₂热催化转化制甲醇过程中CO₂吸附、活化较困难及副产物较多的问题,提出采用单原子Ge助剂修饰Cu (111)晶面的解决思路,通过密度泛函理论(DFT)计算研究了CO₂在Ge-Cu(111)晶面上加氢合成甲醇的反应机理。结果表明,单原子Ge助剂的电子调控增加了与其相邻的Cu原子的电子云密度,使CO₂分子在含Ge活性界面上的吸附能力显著增强：CO₂在Ge-Cu(111)晶面上的吸附能约为Cu (111)晶面的1.5倍,约为Pd改性Cu(111)晶面的2.4倍,进而使逆水煤气变换(RWGS)反应路径速控步骤的活化能降低了近20 kJ·mol^-1,同时衍生出3条生成甲醇的RWGS新路径;此外,Ge-Cu(111)晶面上甲酸盐路径由于速控步骤活化能大幅上升而被禁阻,进而CO及烃类等副产物选择性大幅降低,Ge-Cu(111)晶面上CO₂加氢制甲醇选择性升高。     

原位光化学还原法制备Ag-UiO-66-NH2复合物以增强其光催化性能

采用原位光化学还原沉积法,通过大功率氙灯照射AgNO₃和UiO-66-NH₂混合溶液制备了系列Ag-UiO-66-NH₂复合材料（X min-Ag-UiO-66-NH₂,X为照射时间）。以粉末X射线衍射（PXRD）、傅里叶变换红外光谱（FTIR）、扫描电镜（SEM）、透射电镜（TEM）、高倍透射电镜（HRTEM）、紫外-可见漫反射（UV-Vis DRS）、X射线光电子能谱（XPS）等手段对X-Ag-UiO-66-NH₂的形貌和结构进行了表征。在低功率LED可见光下照射下,对X-Ag-UiO-66-NH₂光催化还原六价铬（Cr（Ⅵ））的性能进行了探究。其中,30min-Ag-UiO-66-NH₂在低功率LED照射40 min对应的Cr（Ⅵ）（初始浓度为10 mg·L^-1）的还原效率为94%,照射60 min可将Cr（Ⅵ）彻底还原。同时,还研究了不同pH值（pH=2,3,4,6,8）、小分子有机酸（草酸、柠檬酸和酒石酸）和外来离子（湖水、自来水和模拟海水）对30 min-Ag-UiO-66-NH₂光催化还原Cr（Ⅵ）的影响。30 min-Ag-UiO-66-NH₂经过5次光催化还原Cr（Ⅵ）循环实验后仍能在照射80 min内实现100% Cr（Ⅵ）还原,表明其具有良好的可重复利用性和稳定性。通过光致发光技术（PL）、电化学测试、电子自旋共振（ESR）和活性物质捕获实验,对光催化还原Cr（Ⅵ）的机理进行了研究和验证。总之,原位光化学还原沉积形成的Ag纳米颗粒有助于改善Ag-UiO-66-NH₂复合材料界面上的电荷转移,从而促进光催化效率的提升。     

磺酸功能化金属-有机骨架吸附脱氮性能

以硝基甲烷为溶剂,采用三氟甲磺酸酐(Tf2O)和浓硫酸对金属有机骨架材料MIL-101(Cr){Cr3F(H2O)2O[(O2C)-C6H4-(CO2)]3nH2O(n~25)}进行磺酸功能化修饰,使其孔壁配体上形成磺酸基团.通过改变MIL-101(Cr)、Tf2O和浓硫酸的摩尔配比,得到含有不同磺酸基团数量的S-MIL-101(Cr),对磺化后的材料进行了X射线衍射(XRD)、傅里叶变换红外(FTIR)、氮气物理吸附、酸碱电位滴定以及热重分析(TGA)表征.结果表明,磺酸功能化后MIL-101(Cr)的孔道结构仍然保持,比表面积和孔径有所下降,表面磺酸基团的数量根据磺化程度的不同从0.21到0.42 mmol g-1不等.将磺酸功能化后的MIL-101(Cr)用于液体燃料的吸附脱氮,发现磺酸功能化能够增强MIL-101(Cr)与含氮化合物的相互作用,有利于其对碱性氮化物的吸附脱除.相对于未经磺化的样品,按照摩尔配比n(MIL-101(Cr)):n(H2SO4):n(Tf2O)=1:3:4.5反应得到的磺酸功能化MIL-101(Cr)对喹啉和吲哚的吸附量提高较大,其对喹啉和吲哚的Langmuir最大吸附量分别提高了12.2%和6.3%.通过乙醇洗涤,吸附剂可再生,经过三次再生之后的吸附剂对模拟燃料中含氮化合物的吸附量没有明显的降低.     

苯部分加氢制环己烯新型Ru-B/MOF催化剂

制备了多种金属-有机骨架(MOF)材料,采用浸渍-化学还原法制备了非晶态Ru-B/MOF催化剂,考察了它们在苯部分加氢反应中的催化性能.催化性能评价结果表明,这些催化剂的初始反应速率(r0)顺序为Ru-B/MIL-53(Al)Ru-B/MIL-53(Al)-NH2Ru-B/UIO-66(Zr)Ru-B/UIO-66(Zr)-NH2Ru-B/MIL-53(Cr)Ru-B/MIL-101(Cr)Ru-B/MIL-100(Fe),环己烯初始选择性(S0)顺序为Ru-B/MIL-53(Al)≈Ru-B/MIL-53(Cr)Ru-B/UIO-66(Zr)-NH2Ru-B/MIL-101(Cr)Ru-B/MIL-53(Al)-NH2Ru-B/UIO-66(Zr)≈Ru-B/MIL-100(Fe).催化性能最好的Ru-B/MIL-53(Al)催化剂上的r0和S0分别为23 mmol·min-1·g-1和72%.采用多种手段,对催化性能差异最为显著的Ru-B/MIL-53(Al)和Ru-B/MIL-100(Fe)催化剂的物理化学性质进行了表征.发现MIL-53(Al)载体能够更好地分散Ru-B纳米粒子,粒子的平均尺寸为3.2 nm,而MIL-100(Fe)载体上Ru-B纳米粒子团聚严重,粒径达46.6 nm.更小的粒径不仅能够提供更多的活性位,而且也有利于环己烯选择性的提高.对Ru-B/MIL-53(Al)催化剂的反应条件进行了优化,在180°C和5 MPa的H2压力下,环己烯得率可达24%,展示了MOF材料用作苯部分加氢催化剂载体的良好前景.     

Adsorption separation of CO2 and N2 on MIL-101 metal-organic framework and activated carbon

In this work, the CO₂ and N₂ adsorption properties of MIL-101 metal-organic framework (MOF) and activated carbon (AC) were investigated using a standard gravimetric method within the pressure range of 0–30 bar and at four different temperatures (298, 308, 318 and 328 K). The dual-site Langmuir–Freundlich (DSLF) model was used to describe the CO₂ adsorption behaviors on these two adsorbents. The diffusion coefficients and activation energy E _a for diffusion of CO₂ in the MIL-101 and AC samples were estimated separately. Results showed that the isosteric heat of CO₂ adsorption on the MIL-101 at zero loading was much higher than that on the AC due to a much stronger interaction between CO₂ molecule and the unsaturated metal sites Cr³⁺ on MIL-101. Meanwhile, the dramatically decreased isosteric heats of CO₂ adsorption on MIL-101 indicated a more heterogeneous surface of MIL-101. Furthermore, the adsorption kinetic behaviors of CO₂ on the two samples can be well described by the micropore diffusion model. With the increase of temperature, the diffusion coefficients of CO₂ in the two samples both increased. The activation energy E _a for diffusion of CO₂ in MIL-101 was slightly lower than that in AC, suggesting that MIL-101 was much favorable for the CO₂ adsorption. The CO₂/N₂ selectivities on MIL-101 and AC were separately estimated to be 13.7 and 9.2 using Henry law constant, which were much higher than those on other MOFs.     

Adsorption of antimony using amino-functionalized magnetic MIL-101(Cr): Optimization by response surface methodology

Amino-functionalized magnetic MIL-101(Cr) was prepared via a one-step solvothermal method, characterized, and applied in adsorptive Sb(III) removal. The effects of solution pH, adsorbent dosage, and coexisting substances on the adsorption of Sb(III) by MIL-101(Cr)–NH₂/MnFe₂O₄ were studied. The adsorption kinetics were analyzed using pseudo-first order, pseudo-second order, intraparticle diffusion, and Elovich models, while Freundlich and Langmuir isotherm models were used to fit the experimental data. The pseudo-second-order kinetic model provided the best fit for the kinetic data. The maximum adsorption capacity of MIL-101(Cr)–NH₂/MnFe₂O₄ for Sb(III) was 91.07 ​mg/g, as calculated using the Langmuir adsorption isotherm model. Thermodynamic analysis revealed that the adsorption of antimony onto MIL-101(Cr)–NH₂/MnFe₂O₄ is spontaneous and endothermic, while response surface optimization revealed that the optimal conditions for Sb(III) adsorption by MIL-101(Cr)–NH₂/MnFe₂O₄ are an adsorbent loading of 222.55 ​mg/L, a pH of 4.5, and a temperature of 294.59 ​K. The predicted adsorption capacity of MIL-101(Cr)–NH₂/MnFe₂O₄ for Sb(III) is only a 1.8% deviation from the actual value. Furthermore, MIL-101(Cr)–NH₂/MnFe₂O₄ exhibits strong magnetism, allowing it to be separated from wastewater using a magnet. Finally, a preliminary economic analysis showed that the cost of treating a ton wastewater containing 25 ​mg/L antimony using this composite would be 26.24 USD. Thus, MIL-101(Cr)–NH₂/MnFe₂O₄ is promising for treatment of Sb(III)-containing wastewater.     

The Significance of Metal Coordination in Imidazole-Functionalized Metal–Organic Frameworks for Carbon Dioxide Utilization

The grafting of imidazole species onto coordinatively unsaturated sites within metal–organic framework MIL-101(Cr) enables enhanced CO₂ capture in close proximity to catalytic sites. The subsequent combination of CO₂ and epoxide binding sites, as shown through theoretical findings, significantly improves the rate of cyclic carbonate formation, producing a highly active CO₂ utilization catalyst. An array of spectroscopic investigations, in combination with theoretical calculations reveal the nature of the active sites and associated catalytic mechanism which validates the careful design of the hybrid MIL-101(Cr).     

乙二胺改性轻金属铝-金属有机骨架材料用于CO_2/CH_4分离

胺类分子在CO_2的捕获中可以起到选择性提升的作用,本文选择小尺寸的乙二胺分子对具有不饱和金属位点的轻金属铝基金属有机骨架(Al-MOFs)材料MIL-100Al进行改性,利用XRD、N2吸附和FT-IR等对改性材料的结构进行表征,测试了不同浓度的乙二胺改性的MIL-100Al对CO_2和CH4吸附性能。结果表明,与原始的MIL-100Al材料相比,改性后的材料对CO_2吸附量有明显提高,CH4的吸附量却降低,从而进一步提高了材料的CO_2/CH4吸附选择性,提升了吸附分离的效果。     

Experimental and molecular simulation studies of CO2 adsorption on zeolitic imidazolate frameworks: ZIF-8 and amine-modified ZIF-8

ZIF-8 has been rapidly developed as a potential candidate for CO₂ capture due to its low density, high surface area, and robust structure. Considering the electron-donating effect of amino functional groups, amino-modification is expected to be an efficient way to improve CO₂ adsorption of ZIF-8. In this work, grand canonical Monte Carlo (GCMC) simulation was performed to study the CO₂ adsorption isotherm based on ZIF-8, ZIF-8-NH₂, and ZIF-8-(NH₂)₂. ZIF-8 was synthesized and CO₂ adsorption isotherms based on ZIF-8 was measured. The experimental surface area, pore volume, and CO₂ adsorption isotherm were used to validate the force field. Adsorptive capacity of ZIF-8-NH₂, and ZIF-8-(NH₂)₂ were first estimated. The GCMC simulation results indicated that the order of increasing CO₂ capacity of the ZIF-8 in the lower pressure regime is: ZIF-8 < ZIF-8-NH₂ < ZIF-8-(NH₂)₂, and in the high pressure is: ZIF-8 < ZIF-8-(NH₂)₂ < ZIF-8-NH₂. New adsorption sites can be generated with the existence of-NH₂ groups. In addition, for non-modified and amino-modified ZIF-8, it was the first time to use density functional theory (DFT) calculations to investigate their CO₂ adsorption sites and CO₂ binding energies. The present work indicates that appropriate amine-functionalized can directly enhanced CO₂ capacity of ZIF-8.