IL-assisted synthesis of defect-rich polyaniline/NH2-MIL-125 nanohybrids with strengthened interfacial contact for ultra-fast photocatalytic degradation of acetaldehyde under high humidity

A novel strategy and design for ionic liquid (IL) assisted in-situ grafting of polyaniline (PANI) oligomers in NH2MIL-125 was proposed to synthesize the defect-rich IL-PANI/NMIL(Ti) nanohybrids with an intimate interface for the superior photodegradation of CH3CHO. PANI was dissolved into small oligomers with the aid of IL [EMIM]BF4 and was composited to NH2-MIL-125 by a strong interfacial connection through Ti-N bonds (XPS) with high dispersion and large surface area (BET = 1125 m2/g). Characterizations results showed that smart grafting of PANI-oligomers generated abundant defects (3.4-times, ESR) and intensified Lewis acid sites (1.2 times, CO-DRIFT) in IL-PANI/NMIL(Ti) compared to NH2-MIL-125. It promoted adsorptive interactions for aldehyde VOCs capturing, which in-turn increased the adsorption rate (ka) of CH3CHO. Smart grafting also improved the light absorption of IL-PANI/NMIL(Ti) from 500 to 800 nm, reduced band gap (1.7 eV), increased photo-current density (2.2-folds of pure MOF), enhanced center dot O-2(-) and center dot OH radicals generation and improved e(-)/h(+) mobility. As a result, IL-PANI/NMIL(Ti) showed 11.4 and 4.2 times higher k(a) (0.262 min(-1)) of CH3CHO photodegradation kinetics than PANI and NH2-MIL-125, respectively, at 75% relative humidity (RH). The k(a) of CH3CHO degradation was steadily increased with increasing humidity (<80 RH%), indicating that H2O from humid air was beneficial for CH3CHO degradation. Furthermore, IL-PANI/NMIL(Ti) exhibited the excellent recycling stability compared to NH2-MIL-125, as only a 5% decrease in photocatalytic activity was observed after five cycling runs. Considering the excellent photostability and ultrafast photodegradation of CH3CHO, the current study opens up new perspectives in fabricating MOFs for a wide-range of practical applications.

Automated summary

The novel IL-PANI/NMIL(Ti) nanohybrids exhibit superior photodegradation performance for CH3CHO with abundant defects and enhanced catalytic activity. Smart grafting increases the adsorption rate of CH3CHO and expands the light absorption range. Furthermore, the degradation rate of CH3CHO is further enhanced at higher humidity levels.