Redox-active metal-organic frameworks for the removal of contaminants of emerging concern

Abstract

The pollution due to the presence of contaminants of emerging concern (CECs) is a major cause for concern because of the serious threat it supposes to human health and ecosystem functions. Many efforts have been geared toward their removal to guarantee safer freshwater.Metal-organic frameworks (MOFs) are crystalline hybrid materials with high surface area and flexible rational design, which allows the incorporation of different active sites into a particular framework, thereby emerging as a potentially excellent candidate for water and wastewater treatment. Benefiting from the unique redox-active properties of MOFs, this review surveys literature update on their application for the removal of CECs. The underlaying electron transfer mechanism and strategies for incorporating redox-active sites into MOFs are comprehensively discussed. Different components of MOFs that are redoxactive are further highlighted. This study elaborates the application of MOFs for Fenton-type and other advanced oxidation processes (AOPs) for removing emerging contaminants. AOPs generate highly reactive strong oxidants like hydroxyl and sulfate radicals that are efficient for degrading emerging pollutants with high mineralization rates. MOFs display semiconductor-like properties. Their photocatalytic use for the removal of dissolved emerging pollutants is detailed in the discussion. This review also provides an overview of the most promising directions for future research.

Fenton-like Cerium Metal–Organic Frameworks (Ce-MOFs) for Catalytic Oxidation of Olefins, Alcohol, and Dyes Degradation

“…Fenton and Fenton-like reaction using nanomaterials advanced catalytic oxidation of organic pollutants for degradation and water treatment [10,15]. These reactions are called advanced oxidation processes (AOPs) [16]. The reaction generates highly oxygen reactive species (ROS) or hydroxyl radicals ( • OH) via the reaction between a catalyst and H 2 O 2 .…”

Photocatalytic activation of peroxodisulfate using iron-containing MOFs synthesized by single-crystal-to-single-crystal transformation for ofloxacin degradation

“…9,10 Recently, iron-containing MOFs (Fe-MOFs) have been widely used for the photocatalytic activation of PMS/PDS due to their diverse structures, good stability, and low cost. 11,12 Zhang et al reported a photocatalytic system with MIL-88A(Fe) as a photocatalyst for the degradation of tetracycline hydrochloride. 13 The photogenerated electrons (e À ) could be captured by PDS to generate SO 4 À radicals, which improved the degradation efficiency.…”

Boosted Activity of g-C3N4/UiO-66-NH2 Heterostructures for the Photocatalytic Degradation of Contaminants in Water

“…Titanium dioxide has been exploited as a semiconductor for water photocatalytic applications due to its abundance, inexpensiveness, low toxicity, and bandgap energy of approximately 3.2 eV, which allows photo-excitation with radiation up to 387 nm [ 13 ]. However, great efforts have been paid to overcome the main limitations of titanium dioxide as a semiconductor, i.e., limited absorption of the solar spectrum in the visible region and the high recombination rate of the photo-generated electron–hole pair [ 14 ].…”

“…Metal–Organic Frameworks (MOFs) are porous structures built by metal oxo clusters or secondary building units (SBU) and organic linkers acting as a bridge between the SBU. As a result, a highly porous structure with active redox behavior is produced, which can be used as a potential photocatalyst for water purification [ 13 , 17 ]. MOFs display the advantage of an easy design of certain properties such as the size of the porous cages by selecting appropriate organic ligands, or the tuning of the photocatalytic response by the functionalization of the ligand with certain organic groups.…”