Highly Advanced Degradation of Thiamethoxam by Synergistic Chemisorption-Catalysis Strategy Using MIL(Fe)/Fe-SPC Composite with Ultrasonic Irradiation.

MIL(Fe)/Fe-SPC composite was fabricated from MIL-100(Fe) via in-situ growth on a unique Fe-doped nano-spongy porous biocarbon (Fe-SPC) and was used as Fenton-like catalyst for advanced degradation of thiamethoxam (THIA). Fe was loaded on a silkworm excrement and calcined to Fe-SPC with nano-spongy and high sp2 C structure. The in-situ growth strategy embedded the Fe-SPC into MIL-100(Fe) crystals and formed conductive heterojunctions with intensified interface by Fe-bridging effect which was confirmed by negative shift of Fe3+ binding energy in XPS. MIL(Fe)/Fe-SPC composites exhibited high degree of crystallinity and surface area (BET: 1730 m2 /g). LC-MS and DFT simulations demonstrated that THIA was converted to a relatively stable compound (C4 H5 N2 SCl), which could be captured by MIL-100(Fe) with strong chemical bonding energy (Fe-N, -587 kJ/mol), followed by a significant geometric distortion, resulting in a thorough degradation. Efficient charge separation and synergistic chemisorption-catalysis strategy resulted in the high catalytic activity of MIL(Fe)/Fe-SPC. The composite catalyst concurrently exhibited high mineralization ratio with 95.4% total organic carbon removal (at 25 ºC and 180 min) and good recycling ability under wider neutral/alkaline conditions. Endorsing to these intriguing properties, MIL(Fe)/Fe-SPC can be deemed an efficient contender for removal of hard-degradable pesticides and other environmental pollutants in practical applications.