Wood modification for the synthesis of MOF@wood composite materials with increased metal–organic framework (MOF) loading

Abstract

For potential applications it is necessary to shape metal-organic frameworks (MOFs) into composite materials. Due to its naturally porous and highly ordered structure, wood is a candidate for the synthesis...

Magnetic Induction Heating-Driven Flow Chemistry Enabling Uniform and Continuous Growth of Metal–Organic Frameworks in Confined Microchannels of Wood

“…Considering that compared to hardwood, softwood generally contains longitudinal tracheid cells with larger microchannels and higher porosity, which would facilitate the access of reactant liquors into wood microchannels, softwood has attracted particular interest for the synthesis of MOF@wood composites. − Based on this, balsa wood, a typical softwood consisting of numerous tubular cells with ultrathin cell walls, was chosen as a scaffold to synthesize MWs and MOF@wood composites in our current work. Prior to MW synthesis, a cylindrical natural balsa wood stick was first cut into blocks with varied sizes (5 mm diameter; 1, 3, and 5 cm lengths, Figure a), followed by a NaOH treatment to enhance their surface affinities toward metal ions according to the previously reported method. , Assisted by a micropump, aqueous Fe 3 O 4 precursor solutions were then forced to flow through the microchannel arrays of the pretreated wood.…”

“…Distinct from our currently presented MHFC synthetic strategy, all of the previously reported wood-based materials were commonly prepared by infiltrating reactant solutions into wood with the vacuum impregnation method, followed by traditional heating such as oil-bath heating. − , To highlight the advantages of our currently developed MHFC synthetic strategy, control experiments on the synthesis of MWs and HKUST-1@MWs were, respectively, conducted by diffusing the same MNP and HKUST-1 mother liquor into the same wood blocks (Figure a) with the commonly utilized vacuum impregnation method and oil-bath heating. The resulting MWs with 1, 3, and 5 cm were denoted MW-C1, MW-C3, and MW-C5, respectively.…”

“…MOF@wood composites have conventionally been synthesized through a batch-based, in situ approach involving the infiltration of MOF mother liquors into wood blocks using the vacuum impregnation method, followed by the in situ growth of MOF crystals on the inner surfaces of wood under traditional solvothermal conditions. − In such a synthetic process, however, MOF mother liquors could penetrate only the microchannels of wood to a very limited depth, typically less than 1 cm, due to the substantial mass transfer resistance. This limitation inevitably led to the creation of MOF@wood composites with uneven MOF distributions and low MOF loadings, typically below 10 wt %. − As a result, the performance of MOF@wood composites was significantly compromised, especially when working with larger, bulkier wood blocks featuring longer microchannels. Furthermore, during the traditional solvothermal reactions within wood, the simultaneous growth of free MOF crystals as a side product in the reaction medium inevitably occurred alongside the MOFs loaded into the wood.…”

“…This competitive formation of free MOFs added to production costs and further diminished the MOF loadings within the wood structure. Another drawback of this traditional in situ synthetic approach was its inherently batch-based production mode, − making the process not only labor-intensive and time-consuming but also unsuitable for scaling up. Clearly, the existing in situ synthetic strategy posed significant challenges in achieving MOF@wood composites with uniform MOF distributions and high MOF loadings in a straightforward, cost-efficient, and scalable manner, especially when dealing with bulkier wood specimens with lengthy microchannels.…”