Scalable Topochemical Synthesis of a Pseudoprotein in Aerogel for Water-Capturing Applications

The peptide N3-Phe-Phe-NHCH2C≡CH self-assembles through hydrogen bonding to form a gel in various solvents. The molecules arrange as β-sheets in the gel as evident from 1H NMR and FT-IR spectroscopy. Upon heating the aerogel made from these gels, the peptide undergoes topochemical azide–alkyne cycloaddition polymerization to form a pseudoprotein as monitored by NMR, IR, DSC, and MALDI analyses. The aerogel absorbs water from the atmosphere contemporaneously with the reaction to fill the voids generated in the pseudoprotein crystal lattice during the reaction, and it desorbs water upon mild heating. The reversible sorption–desorption was proved by thermogravimetric analysis. Dynamic vapor sorption analysis revealed that the pseudoprotein absorbs water at relative humidity (RH) above 30% and releases water when the RH decreases to 20%. Exploiting the scalability and processability of gels, the use of this water-capturing pseudoprotein in atmospheric water harvesting and making self-desiccating containers is demonstrated.