Enhancing the quantum yield of singlet oxygen: photocatalytic degradation of mustard gas simulant 2-chloroethyl ethyl sulfide catalyzed by a hybrid of polyhydroxyl aluminum cations and porphyrin anions.

By combining the anionic salt meso-tetra(4-carboxyphenyl)porphyrin (TCPP 4- ) and the Keggin polyoxometalate cation cluster [Al 13 O 4 (OH) 24 (H 2 O) 12 ] 7+ via a simple ion-exchange method, a hybrid (C 48 H 26 N 4 O 8 )[Al 13 O 4 (OH) 24 (H 2 O) 12 ] 2 (OH) 10 ·18H 2 O (Al 13 -TCPP) was prepared and thoroughly characterized as a prototype of polyoxometalate-porphyrin hybrids for the photocatalytic degradation of the mustard gas simulant 2-chloroethyl ethyl sulfide (CEES). The experimental results showed that the catalytic degradation rate of CEES in the presence of Al 13 -TCPP reached 96.16 and 99.01% in 180 and 90 min in methanol and methanol-water solvent mixture (v/v = 1 : 1), respectively. The reaction followed first-order reaction kinetics, and the half-life and kinetic constant in methanol and solvent mixture were 39.8 min, -0.017 min -1 and 14.7 min, -0.047 min -1 . Mechanism analysis indicated that under visible light irradiation in air, CEES was degraded through a combination of oxidation and alcoholysis/hydrolysis in methanol and the methanol-water solvent mixture. The superoxide radical (O 2 ˙ - ) and singlet molecular oxygen ( 1 O 2 ) generated by Al 13 -TCPP selectively oxidized CEES into a non-toxic sulfoxide. The singlet oxygen capture experiments showed that Al 13 -TCPP ( Φ = 0.236) had a higher quantum yield of singlet oxygen generation than H 4 TCPP ( Φ = 0.135) under visible light irradiation in air. The material Al 13 -TCPP has good reusability, and the degradation rate of CEES can still reach 98.37% after being recycled five times.