Mechanistic fusion of homolytic H2O2 scission and radical inter-conversion to sustain supported phosphate radicals for aqueous toxicant degradation

Abstract

ZrO2 bears Lewis acidic Zr4+ (LA) and Bro<spacing diaeresis>nsted acidic-OH (BA--H+) available to interact with O and H of H2O2, respectively. This activates sustainable, Zr4+ leaching-free H2O2 homolysis to impart two center dot OH, whose desorption from LA/BA--H+ is the rate-determining step and is more vigorous with higher LA/BA--H+ strengths (ELA/EBA-H+). Given ZrO2&apos;s high oxophilicity, ELAis challenging to modulate, whereas EBA-H+ remains tunable. To combine the merits of ZrO2 stated above and those of H3-APO4(A-1)center dot- (A=1-3) emerging, we functionalized ZrO2 with H3-APO4A-to yield H3-APO4 A-SUP supported on ZrO2 (ZrO2-P). P+-O-/P+-O--H+ in H3-APO4 A-SUP withdrew electrons (e-) away from vicinal LA/BA--H+, leading to make ELA/EBA-H+ of ZrO2-P higher than those of ZrO2. Moreover, P+-O-underwent center dot OH-assisted transformation into P+-O center dot via radical inter-transition, whose rate-determining step is center dot OH desorption. Furthermore, P+-O--H+ acted as additional BA--H+ utilized to activate H2O2 homolysis. ZrO2-P with multi-functional H3-APO4 A-SUP moieties was superior to ZrO2 in lowering the energy barrier required for center dot OH desorption, thus achieving higher center dot OH/H3-APO4 SUP productivities under H2O2-containing aqueous phases. ZrO2-(A-1)center dot- P and ZrO2 deployed H3-APO4 SUP and center dot OH, respectively, as the primary toxicant disintegrators. Consequently, (A-1)center dot- ZrO2-P outperformed ZrO2 to efficiently or sustainably fragment analgesic, pesticide, antibiotic, or chemical warfare agent (paraoxon-methyl/VX), either of which contains e--donating groups labile to destabilization via H3-APO4 SUP-enabled e-transfer rather than via center dot OH-enabled addition/H center dot abstraction. Moreover, paraoxon-(A-1)center dot- methyl fragmentation was more effective with H3-APO4 SUP on ZrO2-P than with H3-APO4 (A-1)center dot- SUP on Fe2O3-P or (A-1)center dot- with NO3 center dot SUP on ZrO2-N.