Biomimetic Photodegradation of Glyphosate in Carborane-Functionalized Nanoconfined Spaces

The removal of organophosphorus (OP) herbicides fromwater hasbeen studied using adsorptive removal, chemical oxidation, electrooxidation,enzymatic degradation, and photodegradation. The OP herbicide glyphosate(GP) is one of the most used herbicides worldwide, leading to excessGP in wastewater and soil. GP is commonly broken down in environmentalconditions to compounds such as aminomethylphosphonic acid (AMPA)or sarcosine, with AMPA having a longer half-life and similar toxicityto GP. Metal-organic frameworks (MOFs) are excellent materialsfor purifying OP herbicides from water due to their ability to combineadsorption and photoactivity within one material. Herein, we reportthe use of a robust Zr-based MOF with a meta-carboranecarboxylate ligand ( mCB-MOF-2) to examinethe adsorption and photodegradation of GP. The maximum adsorptioncapacity of mCB-MOF-2 for GP was determinedto be 11.4 mmol/g. Non-covalent intermolecular forces between thecarborane-based ligand and GP within the micropores of mCB-MOF-2 are thought to be responsible for strongbinding affinity and capture of GP. After 24 h of irradiation withultraviolet-visible (UV-vis) light, mCB-MOF-2 selectively converts 69% of GP to sarcosine and orthophosphate,following the C-P lyase enzymatic pathway and biomimeticallyphotodegrading GP. Circumventing the production of AMPA is desirable,as it has a longer half-life and similar toxicity to GP. The exceptionaladsorption capacity of GP by mCB-MOF-2 and its biomimetic photodegradation to non-toxic sarcosine makeit a promising material for removing OP herbicides from water.