Vellingiri Kowsalya, Deng Ya-Xin, Kim Ki-Hyun, Jiang Jheng-Jie, Kim Taejin, Shang Jin, Ahn Wha-Seung, Kukkar Deepak, Boukhvalov Danil W
Department of Civil and Environmental Engineering , Hanyang University , 222 Wangsimni-Ro , Seoul 04763 , Korea.
Environmental and Water Resources Engineering Division, Department of Civil Engineering , IIT Madras , Chennai 600 036 , India.
ACS Appl Mater Interfaces. 2019 Jan 9;11(1):1426-1439. doi: 10.1021/acsami.8b17479. Epub 2018 Dec 27.
Porous materials have been identified as efficient sorbent media to remove volatile organic compounds. To evaluate their potential as adsorbents, the adsorptive removal of formaldehyde (FA) in aqueous environments was investigated using four materials, two water-stable metal-organic frameworks (MOFs) of UiO-66 (U6) and U6-NH (U6N) and two covalent organic polymers (COPs) with amine-functionality, CBAP-1-EDA (CE) and CBAP-1-DETA (CD). U6N exhibited the highest removal capacity of 93% (0.56 mg g) of the tested materials [e.g., CE (81.1%, 0.53 mg g) > CD (67.2%, 0.43 mg g) > U6 (66.9%, 0.42 mg g)], which was 2 times higher than that of the reference sorbent, activated carbon (AC: 50%, 0.30 mg g). The results of Fourier transform infrared and powder X-ray diffraction analyses confirmed the interactions between FA molecules and the amine components of the materials (U6N, CD, and CE). According to density functional theory calculations, the formation of hydrogen bonds between FA molecules and amine components was apparent and was further verified by FA/amine distance (CD: 2.83, CE: 2.88, and U6N: 2.66 Å) along with enthalpy values (CD: -32.4, CE: -45.5, and U6N: -272 kJ mol). In case of U6, the major interactions occurred in the metal-clusters (-19.3 kJ mol) via electrostatic interactions (distance: 5.49 Å). Furthermore, the sorption by amine-functionalized materials such as U6N is suggested to be dominated by hydrogen bonding which ultimately led to the formation of imine. If the performance of the tested materials is evaluated in terms of partition coefficient, U6N (1153 mg g mM) is found as the outperformer in all tested subjects. Regeneration of spent MOFs/COPs was also plausible in the presence of ethanol to maintain their structural integrity even after 10 adsorption-desorption cycles. Overall, the selected MOFs/COPs were seen to have very high removal capacity for hazardous FA molecules in aqueous phase.
多孔材料已被确认为去除挥发性有机化合物的高效吸附剂介质。为了评估它们作为吸附剂的潜力，使用四种材料研究了在水环境中对甲醛（FA）的吸附去除情况，这四种材料分别是两种水稳定的金属有机框架（MOF）——UiO - 66（U6）和U6 - NH（U6N），以及两种具有胺官能团的共价有机聚合物（COP）——CBAP - 1 - EDA（CE）和CBAP - 1 - DETA（CD）。在测试材料中，U6N表现出最高的去除能力，为93%（0.56 mg/g）[例如，CE（81.1%，0.53 mg/g）> CD（67.2%，0.43 mg/g）> U6（66.9%，0.42 mg/g）]，这比参考吸附剂活性炭（AC：50%，0.30 mg/g）高出2倍。傅里叶变换红外光谱和粉末X射线衍射分析结果证实了FA分子与材料（U6N、CD和CE）中的胺成分之间存在相互作用。根据密度泛函理论计算，FA分子与胺成分之间明显形成了氢键，并通过FA/胺的距离（CD：2.83，CE：2.88，U6N：2.66 Å）以及焓值（CD： - 32.4，CE： - 45.5，U6N： - 272 kJ/mol）进一步得到验证。对于U6而言，主要相互作用通过静电相互作用（距离：5.49 Å）发生在金属簇中（ - 19.3 kJ/mol）。此外，像U6N这样的胺官能化材料的吸附作用被认为主要由氢键主导，最终导致亚胺的形成。如果根据分配系数来评估测试材料的性能，U6N（1153 mg/g mM）在所有测试对象中表现最佳。在乙醇存在的情况下，用过的MOF/COP也可以再生，即使经过10次吸附 - 解吸循环后仍能保持其结构完整性。总体而言，所选的MOF/COP在水相中对有害的FA分子具有非常高的去除能力。
