An Eco‐Friendly, Tunable and Scalable Method for Producing Porous Functional Nanomaterials Designed Using Molecular Interactions

Abstract

Despite significant improvements in the synthesis of templated silica materials, post‐synthesis purification remains highly expensive and renders the materials industrially unviable. In this study this issue is addressed for porous bioinspired silica by developing a rapid room‐temperature solution method for complete extraction of organic additives. Using elemental analysis and N2 and CO2 adsorption, the ability to both purify and controllably tailor the composition, porosity and surface chemistry of bioinspired silica in a single step is demonstrated. For the first time the extraction is modelled using molecular dynamics, revealing that the removal mechanism is dominated by surface‐charge interactions. This is extended to other additive chemistry, leading to a wider applicability of the method to other materials. Finally the environmental benefits of the new method are estimated and compared with previous purification techniques, demonstrating significant improvements in sustainability.

Bioinspired synthesis as a potential green method for the preparation of nanomaterials: Opportunities and challenges

“…0.9 ton CO 2 e/ton SiO 2 , the aqueous acid elution method developed in Ref. [34] produced only 0.01 ton CO 2 e/ton SiO 2 , a 97% reduction.…”

“…Significant effort has been expended in attempting to avoid this, with effective solvent removal being touted as an excellent alternative to traditional lab-scale calcination [27]. However, refluxing solvents, which is generally required during removal, can actually push the energy intensity of these removal methods above those of calcination [34]. Redesign of the organic molecule has therefore gone a long way towards achieving milder surfactant removal, especially with regards to (bio-)degradable additives [35] or additives with tailored, softer surface interactions to enable milder removal [36e38].…”

“…Adoption of bioinspired methods also has advantages beyond the reaction step e one of the largest energy demands for production of surfactant-templated materials lies in the surfactant removal stage of the process [34]. Significant effort has been expended in attempting to avoid this, with effective solvent removal being touted as an excellent alternative to traditional lab-scale calcination [27].…”

“…Redesign of the organic molecule has therefore gone a long way towards achieving milder surfactant removal, especially with regards to (bio-)degradable additives [35] or additives with tailored, softer surface interactions to enable milder removal [36e38]. Here, bioinspired additives have been shown to be better for post-synthetic extraction in addition to producing milder syntheses [34]. By taking advantage of biological interactions and motifs, additives have weaker individual binding with the inorganic bioinspired material than fully synthetic alternatives, allowing for easier disruption of the interactions used to synthesise the molecule hence enabling easier extraction and potential reuse of the additives (see Figure 2biii).…”

“…Bioinspired methods utilise additives, which remain in the final product as impurities. The downstream purification is highly energy demanding and environmentally damaging [34,38]. As a result, there is a strong need for greener downstream purification (e.g.…”