Hierarchical 3D inverse opal MOF composites for synergistic toluene adsorption-photothermal desorption

Metal-organic framework (MOF)/photothermal composites typically suffer from the intrinsic trade-off between adsorption capacity and photothermal regeneration efficiency, limiting their synergistic adsorption-desorption performance. Cu-based MOF (HKUST-1) crystals were grown on photothermal inverse opal polypyrrole (IOPPy) with abundant surface pyrrole N sites (metal coordination) by microwave-assisted in-situ method and successfully constructed IOPPy(Cu)@HK-M. The abundant N-Cu-O interface bridging in IOPPy(Cu)@HK-M ensured ultrahigh MOF loading (90 wt%) and induced the formation of unsaturated Cu and interface micropores. It enhances toluene capture capacity (1.5 times, P / P 0  = 0.0026) and adsorption kinetics (1.8 times) compared to HKUST-1. During photothermal desorption process, photon localization effect of inverse opal structure significantly enhances the photothermal conversion efficiency to 54%, which is 2.2 times of HKUST-1. The inverse opal structure also promotes efficient energy transfer throughout the system after light conversion and reduces internal temperature gradient, and act on MOFs via N-Cu-O interface, thereby accelerating the desorption of toluene within the MOFs. Hence, IOPPy(Cu)@HK-M achieves a remarkable 99.7% desorption ratio and 2.9 times desorption rate versus HKUST-1 under same energy input. The construction of inverse opal-MOF successfully achieves synergistic enhancement of toluene adsorption/desorption with high efficiency and low energy consumption by reinforcing photothermal conversion efficiency and mass/heat transfer capabilities.