Amen Rabia, Elsayed Islam, Kim Yunsang, Schueneman Gregory T, El-Giar Emad M, Hassan El Barbary
Department of Sustainable Bioproducts, Mississippi State University, P.O. Box 9820, Mississippi State, MS 39762, USA.
Department of Chemistry, Faculty of Science, Damietta University, New Damietta 34517, Egypt.
Gels. 2025 May 15;11(5):365. doi: 10.3390/gels11050365.
UiO-66-NH is a metal-organic framework (MOF) with open metal sites, making it a promising candidate for adsorption and catalysis. However, the powdery texture of MOFs and the use of toxic solvents during synthesis limit their application. A novel solution to this issue is to create a layered porous composite by encasing the MOF within a flexible and structurally robust aerogel substrate using safe, eco-friendly, and green solvents such as ethanol. The fibrous MOF aerogels, characterized by a desirable macroscopic shape of cylindrical block and hierarchical porosity, were synthesized by two approaches: in situ growth of amine-functionalized UiO-66-NH crystals on a TEMPO-oxidized cellulose nanofiber (TOCNF) and ex situ crosslinking of UiO-66-NH crystals onto a TOCNF network to form UiO-66-NH/TOCNF. The incorporation of MOF into the cellulose nanofibrils via the in situ method reduces their aggregation potential, alters the nucleation/growth balance to produce smaller MOF crystals, and enhances mechanical flexibility, as evidenced by SEM images. The three adsorbents, including UiO-66-NH, ex situ UiO-66-NH/TOCNF, and in situ UiO-66-NH/TOCNF, were synthesized and used in this study. The effects of pH, time, temperature, and initial concentration were studied. A maximum adsorption capacity (Qmax) of 549.45 mg/g for Congo Red (CR) and 171.23 mg/g for Orange II (ORII) was observed at pH 6, using 10 mg of in situ UiO-66-NH/TOCNF at 40 °C with a contact time of 75 min for CR and 2 h for ORII. The adsorption of both dyes primarily occurs through monolayer chemisorption on the in situ UiO-66-NH/TOCNF. The main removal mechanisms were hydrogen bonding and surface complexation. The noteworthy adsorption capacity of in situ UiO-66-NH/TOCNF coupled with environment-friendly fabrication techniques indicates its potential applications on a large scale in real wastewater systems.
UiO - 66 - NH是一种具有开放金属位点的金属有机框架（MOF），使其成为吸附和催化领域有潜力的候选材料。然而，MOF的粉末质地以及合成过程中使用有毒溶剂限制了它们的应用。解决这个问题的一个新方法是使用乙醇等安全、环保和绿色的溶剂，将MOF包裹在柔性且结构坚固的气凝胶基质中，从而制备出层状多孔复合材料。通过两种方法合成了具有理想圆柱块状宏观形状和分级孔隙率的纤维状MOF气凝胶：在经2,2,6,6 - 四甲基哌啶 - 1 - 氧自由基（TEMPO）氧化的纤维素纳米纤维（TOCNF）上原位生长胺功能化的UiO - 66 - NH晶体，以及将UiO - 66 - NH晶体异位交联到TOCNF网络上以形成UiO - 66 - NH/TOCNF。通过原位方法将MOF掺入纤维素纳米纤维中可降低其聚集倾向，改变成核/生长平衡以产生更小的MOF晶体，并增强机械柔韧性，扫描电子显微镜（SEM）图像证明了这一点。本研究合成并使用了三种吸附剂，包括UiO - 66 - NH、异位UiO - 66 - NH/TOCNF和原位UiO - 66 - NH/TOCNF。研究了pH值、时间、温度和初始浓度的影响。在40℃下，使用10mg原位UiO - 66 - NH/TOCNF，刚果红（CR）的接触时间为75分钟，橙黄II（ORII）的接触时间为2小时，在pH值为6时，观察到对CR的最大吸附容量（Qmax）为549.45mg/g，对ORII为171.23mg/g。两种染料在原位UiO - 66 - NH/TOCNF上的吸附主要通过单层化学吸附发生。主要去除机制是氢键和表面络合。原位UiO - 66 - NH/TOCNF值得注意的吸附容量以及环保的制备技术表明其在实际废水系统大规模应用中的潜力。
