Stable Aluminum Metal-Organic Frameworks (Al-MOFs) for Balanced CO 2 and Water Selectivity.

Three new Al-MOFs in the formation of [Al4 (OH)2 (OCH3 )4 (OH-BDC)3 ]·xH2 O (BIT-72), [Al4 (OH)2 (OCH3 )4 (CH3 -BDC)3 ]·xH2 O (BIT-73) and {Al4 (OH)2 (OCH3 )4 [(CH3 )2 -BDC]3 }·xH2 O (BIT-74) have been synthesized by assembling Al3+ ion with terephthalic acid ions decorated with monohydroxyl, monomethyl or dimethyl groups, respectively. All of these three MOFs exhibit high stability in boiling water and acidic conditions. Among them, BIT-72 shows the highest surface area of 1618 m2 ·g-1 and IAST CO2 /N2 selectivity of 48, while BIT-73 and BIT-74 present moderate IAST CO2 /N2 selectivity and much lower H2 O capacity below P/P0 = 0.3. The high CO2 /N2 selectivity together with alleviative H2 O sorption at low water relative pressure may provide promising potential in postcombustion CO2 capture.