Synergistic Computational and Experimental Investigation of Covalent Organic Frameworks for Efficient Alcohol
Krishna M Gupta1,2, Srinivasulu Aitipamula1, Xavier Chin1
1Institute of Sustainability for Chemicals, Energy and Environment (ISCE2), Agency for Science, Technology and Research (A*STAR), 1 Pesek Road, Jurong Island, Singapore 627833, Republic of Singapore.
Abstract:
Covalent organic frameworks (COFs), a promising class of nanoporous materials, have received significant attention for membrane separation. Currently, several COFs are reported for alcohol dehydration, but they are not efficient owing to the pervasive challenge to separate small-sized molecular mixture. Herein, first we have computationally explored a series of COFs with different functionality and aperture size as pervaporation (PV) membrane and identified a novel COF for efficient dehydration of water/alcohol mixtures (90 wt % IPA, 90 wt % n-butanol and 90 wt % t-butanol). Subsequently, the best-performing COF was experimentally synthesized and characterized, and its sorption properties were correlated with computational results. Molecular dynamics (MD) simulations revealed that solvent permeation fluxes are predominantly influenced by the pore aperture of COFs, and larger pore aperture exhibits higher flux. Conversely, the separation factor is primarily determined by the polarity of the pore functional groups. Among the tested COF membranes, TpPa-1-OC3H6OCH3 demonstrated superior performance, surpassing the current state-of-the-art membranes. The activation energy (Ea) for water permeation in alcohol mixtures through TpPa-1-OC3H6OCH3 is mostly governed by water-alcohol interactions. Furthermore, experimental evaluation of the COFs indicated a plate-like morphology for TpPa-1-OC3H6OCH3 which ascertained a 2D-sheet-like structure. TpPa-1 showed greater sorption than TpPa-1-OC3H6OCH3 with all of the solvents tested owing to the inability of the solvent molecules to enter the relatively small pores in the later COF. This is in accordance with the MD simulation predictions, which indicated that the solvent molecules cannot penetrate the small pores of TpPa-1-OC3H6OCH3. This work synergistically integrates computational and experimental approaches to develop novel COFs with superior performance compared to previously reported PV membranes, paving the way for advanced membranes for sustainable solvent recovery.
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