All of the chemicals used in this project were purchased from commercial suppliers and were used without further purification. The ligand 4,4′-dihydroxy-[1,1′-biphenyl]-3,3′-dicarboxylic acid (H 4 dobpdc) was purchased from Hangzhou Trylead Chemical Technology. 17 O-enriched CO 2 gas was purchased from ICON/Berry & Associates, Inc, with approximately 20 atom % O.