By linkage of 1,5-naphthalenedisulfonate (1,5-NDS) anion fluorophore, 3D cucurbit[7]uril (CB[7]) framework has been constructed. The maximum solid-state fluorescence wavelength of the CB[7] framework exhibits blue-shift from 406 to 340 nm in comparison with that of 1,5-NDS, which was ascribed to increased excited energy from 0.10 to 0.13 eV according to theoretical calculations.

The unique pumpkin-shape macrocyclic structure with inherent cavities renders cucurbituril (CB) a type of versatile supramolecular container. On account of their good biocompatibility and low toxicity, the applications of CB to encapsulate drug molecules provide promising candidates and the pharmacological activities have been investigated currently. How to control over the uptake and release of the guest at will is significant for practical applications of drug delivery. The noncovalent nature of supramolecular interactions offers variety of options to control the release of guest molecules from CB under external stimuli, including pH, temperature, metal cations, competing guests, light, redox and so on. Moreover, CB containers are capable of assembling into higher ordered supramolecular structures such as polymers, nanoparticles, hydrogels, and colloids, which greatly enrich the scope of CB-type inclusion materials. Those results provide useful principles and guidelines for controlled release from supramolecular containers.

•Acidic ionic liquids catalyzed cellulose depolymerization to levulinic acid.•The highest yield of levulinic acid was 86% under hydrothermal conditions.•A kinetic model was developed based on experimental data.•Catalytic activities mostly depend on acidity and H-bonding ability of anion.•Separation of levulinic acid and reuse of ionic liquid were realized via extraction.Cellulose depolymerization to levulinic acid (LA) was catalyzed by acidic ionic liquids (ILs) selectively and recyclably under hydrothermal conditions. The effects of reaction temperature, time, water amount and cellulose intake were investigated. Dilution effect becomes more pronounced at lower cellulose intake, dramatically improving the yield of LA to 86.1%. A kinetic model has been developed based on experimental data, whereby a good fit was obtained and kinetic parameters were derived. The relationships between IL structure, polymeric structure and depolymerization efficiency were established, shedding light on the in-depth catalytic mechanism of IL, inclusive of acidity and hydrogen bonding ability. The LA product can be readily separated through extraction by methyl isobutyl ketone (MIBK) and IL can be reused over five cycles without loss of activity. This environmentally friendly methodology can be applied to selective production of LA from versatile biomass feedstocks, including cellulose and derivatives, glucose, fructose and HMF.