Dipeptide Porous Crystals as Gas Adsoprtive Materials and Polymerization Nanoreactors

Porous materials are of great interest in several fields because of the multiple functions they can play, e.g. gas storage and separation, catalysis, and the formation of polymers in the confined state.[1] We present a family of microporous materials - peptide-based biozeolites - which can behave as selective hosts for gas and monomer capture and as nanovessels for in situ polymerization. The family of biologically-based microporous materials (based on L-alanine, L-valine, and L-isoleucine), which show nanochannels from 3 to 5 exhibited the selective capture of CO2 versus N2 and other gases as demonstrated by the combination of adsorption isotherms, Grand Canonical solid state NMR and Monte Carlo simulations. The direct CO2 detection by 1D/2D MAS NMR experiments could describe CO2 diffusion within the channels and its intimacy with the solid matrix.[2] Also, molecular hydrogen can diffuse into the crystalline channels and can be absorbed efficiently. The use of dipeptide porous crystals as nanoreactors for in situ solid-state polymerization led to the fabrication of new hybrid synthetic/biological nanostructured materials.[3] Topochemical polymerizations were realized. Moreover, porous dipeptide crystals permitted post-modification reactions to be carried out on polymers confined in their nanochannels. Specifically, PAN was transformed into a polyconjugated ladder polymer and confined carbon nanofibers. The PAN curing in dipeptide crystals suggests an unusual way to produce stretched graphitic carbon fibrils. The possibility of transferring the exquisite order and versatility of porous biological crystals to synthetic polymer structures opens up new opportunities for reactions in biological media.