Computational screening, synthesis and testing of metal-organic frameworks with a bithiazole linker for carbon dioxide capture and its green conversion into cyclic carbonates

Computational crystal construction algorithms were used to create twelve metal-organic frameworks containing a newly synthesized [2,2′-bithiazole]-5,5′-dicarboxylic acid (H 2 TzTz) spacer and assorted transition metal nodes. Among the twelve structures, the zirconium-based MOF of general formula [Zr 6 O 4 (OH) 4 (TzTz) 6 ] ( 1 ) was found to be the best candidate for carbon dioxide uptake, as judged from the results of the grand canonical Monte Carlo (GCMC) simulations of CO 2 adsorption isotherms. Guided by the simulation results, 1 was synthesized in the laboratory and thoroughly characterized. 1 is isoreticular to its bithiophene and bis(benzene) (UiO-67) analogues; it crystallizes in the cubic Pn 3&cmb.macr; space group with fcu topology, and it features octahedral [Zr 6 ] nodes connected by twelve carboxylate groups from six bridging TzTz 2− spacers. It is a predominantly microporous material (micropore volume = 84% of the total pore volume), with a BET area of 840 m 2 g −1 and a maximum CO 2 uptake at ambient pressure of 2.3 mmol g −1 (10.0 wt%) or 1.7 mmol g −1 (7.5 wt%) at 273 or 298 K, respectively. The CO 2 affinity (isosteric heat of adsorption Q st = 18.7 kJ mol −1 ; CO 2 /N 2 Henry selectivity = 10; CO 2 /N 2 IAST selectivity = 8.4) is similar to that of its bithiophene analogue. After partial removal of solvent (activation), 1 was tested as a heterogeneous catalyst in the reaction of CO 2 with epoxides bearing a -CH 2 X pendant arm (X = Cl: epichlorohydrin; X = Br: epibromohydrin) to give the corresponding cyclic carbonates at T = 393 K and p CO 2 = 1 bar under green (solvent- and co-catalyst-free) conditions. A good conversion of 74% and a turnover frequency of 12.3 mmol (cyclic carbonate) per mmol Zr per h have been recorded with epibromohydrin as a substrate. A combined theoretical-experimental approach has been exploited for the design of a zirconium bithiazole-based MOF for CO 2 adsorption and its reaction with epoxides under green conditions.