MOF Triggered Gelation: A Novel Method for Preparation of MOF and Aerogel Composites

A novel method was developed to synthesize composites of Cu-BTC with alginate. The gelation was triggered by the open Cu metal centers which are coordinated to the BTC ligands. The resulting gel was dried supercritically to obtain the aerogel composite. Cu-BTC content in the composite was tuned in to the mass ratio of 1:2 to 2:1 and the resulting materials' BET surface areas ranged between 450 and 1162 m²/g. The equilibrium uptake of CO₂ for AlgA/Cu-BTC (2:1), AlgA/Cu-BTC (1:1), and AlgA/Cu-BTC (1:2) at 1 bar and 298 K was determined as 0.132, 0.325, and 0.434 mmol g^-1, respectively for a binary mixture of 15% CO₂/85% N₂. Uptake values determined by dynamic adsorption experiments were slightly lower than those obtained for single-component CO₂ conditions, which was attributed to competitive adsorption between CO₂ and N₂. The simulated CO₂ adsorption isotherms slightly overestimated the experimental uptake values, which is consistent with the involvement of open Cu metal centers in the gelation of sodium alginate. This is the first time that a MOF is utilized as a gelation triggering agent and is likely to lead to the development of novel nanostructured alginate aerogel/gel composites of MOFs with divalent cation centers.