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

• Concepts and mechanisms of redox activities in metal-organic frameworks (MOFs). • Strategies for incorporating redox-active sites into MOFs. • Redox-active MOFs for wastewater treatment. • MOFs for advanced oxidation processes (AOPs) for the removal of contaminants of emerging concern (CECs). • Photocatalytic MOFs and the mechanisms for removing dissolved emerging pollutants. 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 redox-active 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.