Amine-Functionalized Metal–Organic Frameworks and Covalent Organic Polymers as Potential Sorbents for Removal of Formaldehyde in Aqueous Phase: Experimental Versus Theoretical Study

Abstract

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 2 (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 −1 ) of the tested materials [e.g., CE (81.1%, 0.53 mg g −1 ) > CD (67.2%, 0.43 mg g −1 ) > U6 (66.9%, 0.42 mg g −1 )], which was 2 times higher than that of the reference sorbent, activated carbon (AC: 50%, 0.30 mg g −1 ). The results of Fourier transform infrared and powder Xray 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 −1 ). In case of U6, the major interactions occurred in the metal−clusters (−19.3 kJ mol −1 ) 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 −1 mM −1 ) 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.

Building MOF Nanocomposites with Oxidized Graphitic Carbon Nitride Nanospheres: The Effect of Framework Geometry on the Structural Heterogeneity

“…The diversity of the metal centers and organic ligands leads to materials of particular crystallographic structure, texture, and chemistry. Due to these properties, MOFs have been tested for various applications such as gas separation/storage [4][5][6][7][8][9], purification [10][11][12], sensing [13][14][15][16], electrodes for batteries [17,18], microextraction [19,20], detoxification of chemical warfare agents [21][22][23][24][25], and heterogeneous catalysis [26][27][28].…”

Efficient adsorption of four phenolic compounds using a robust nanocomposite fabricated by confining 2D porous organic polymers in 3D anion exchangers

“…Under most conditions, it was found that all three models had high regression coefficients (R 2 ), suggesting a mixed process of single-and multi-layer adsorption. The results further implied a multi-interaction-driven adsorption process [41], in which electrostatic attraction (single-layer), π-π interaction (multi-layer) and/or H-bonding (either single-or multi-layer) occurs [42].…”

Heterojunction of Pores in Granola‐Type Crystals of Two Different Metal–Organic Frameworks for Enhanced Formaldehyde Removal

“…These findings suggest that the HKUST-1^UiO-66 granules would be efficient for the removal of formaldehyde from the air, as formaldehyde is a sticky compound even at ambient temperature and pressure conditions owing to its strong interaction with adsorbents (43,44). Formaldehyde is an environmentally harmful gas existing in trace amounts in the air (45)(46)(47)(48), and MOFs are promising absorbents for efficiently removing it from the air (49)(50)(51)(52)(53)(54). The formaldehyde removal capacities of the samples were tested using a specially designed process, as shown in Figure 3(a).…”