Water‐Stable Metal Azolate Frameworks Showing Interesting Flexibilities for Highly Effective Bioethanol Dehydration

Abstract

AbstractThe ethanol/water separation challenge highlights the adsorption capacity/selectivity trade‐off problem. We show that the target guest can serve as a gating component of the host to block the undesired guest, giving molecular sieving effect for the adsorbent possessing large pores. Two hydrophilic/water‐stable metal azolate frameworks were designed to compare the effects of gating and pore‐opening flexibility. Large amounts (up to 28.7 mmol g−1) of ethanol with fuel‐grade (99.5 %+) and even higher purities (99.9999 %+) can be produced in a single adsorption process from not only 95 : 5 but also 10 : 90 ethanol/water mixtures. More interestingly, the pore‐opening adsorbent possessing large pore apertures showed not only high water adsorption capacity but also exceptionally high water/ethanol selectivity characteristic of molecular sieving. Computational simulations demonstrated the critical role of guest‐anchoring aperture for the guest‐dominated gating process.