Enhanced moisture-resistance and excellent photocatalytic performance of synchronous N/Zn-decorated MIL-125(Ti) for vaporous acetaldehyde degradation

High photo-catalytic activity and stable recycling performance under high humidity are main hindering factors in practical applications of metal organic frameworks (MOFs) for volatile organic compounds (VOCs) degradation. In-situ co-doping strategy of pyrrolic N/Zn was proposed to enhance surface charge separation and cycling stability of MIL-125(Ti) for degradation of vaporous acetaldehyde under highly humid conditions. Characterizations results show that pyrrolic N/Zn co-doped MIL-125(Ti) exhibited an integrated crystal structure and high surface area (1415 m2/g). The constructed Ti/Zn-N/O clusters narrowed band gap (from 3.40 to 1.85 eV) of MIL-125(Ti) and boosted electron conductivity. Also, it was proved to enhance surface alkalinity and hydrophobicity of MIL-125(Ti), which would strengthen MOFs selective adsorption towards CH3CHO and accelerated the transfer of degradation product CO2 from catalytic active sites in MIL-125(Ti) under high humidity. As a result, synergistic effect of N/Zn co-doping exhibited an enhanced the ability of activating oxygen and H2O molecules into superoxide radical (O2−) and hydroxy radical (OH), showing 10 times faster reaction kinetics for CH3CHO degradation under humid air compared to MIL-125(Ti). Moreover, co-dopant of N/Zn into MIL-125(Ti) has significantly promoted the recycling stability of MIL-125(Ti) under high humidity. According to the work, co-dopant elemental strategy to modify MOF surface can provide the synergistic effect for efficient degradation of aldehyde VOCs under humid conditions.