Carboxylated lamellar wood sponge enables high loading and uniform dispersion of MIL-53(Al) for efficient organic dye adsorption.

Developing high-performance metal-organic framework (MOF)-based composites with high loading and uniform distribution of MOF nanoparticles is crucial for their adsorption-associated applications but remains challenging due to the lack of ideal carriers. Herein, a novel MOF-based composite was developed by in situ growth of MIL-53(Al) crystals within the carboxylated wood sponge (CWS) derived from natural balsa wood. The conversion of the cellular structure of natural wood into a lamellar structure greatly enhances the accessibility of the wood scaffold, while the introduction of carboxyl groups onto the cellulose skeleton of the wood sponge encourages the selective growth of MIL-53(Al) crystals on the lamellae of CWS. The structural features of the obtained MIL-53(Al)@CWS were investigated with FT-IR, XRD, SEM, and N adsorption/desorption isotherms. The MIL-53(Al) loading can be finely tuned by adjusting the concentration of the MOF precursor solutions, and an appropriate MIL-53(Al) loading of 23 wt% results in the uniform dispersion of MIL-53(Al) crystals within the wood sponge without agglomeration. Benefiting from the high loading of MIL-53(Al) and the unique lamellar channels of CWS, the developed MIL-53(Al)@CWS can effectively adsorb various organic dyes such as rhodamine B (RhB), methylene blue, Congo red, and methyl orange in water, with a high adsorption capacity of 135.82 mg g for RhB. Density functional theory (DFT) calculations reveal the detailed dynamic diffusion pathways and the molecular interactions between RhB and MIL-53(Al). This work demonstrates the advantages and potentials of lamellar wood sponges as a promising host matrix in supporting MOF powders for adsorption-associated applications.