A composition having the structure of formula I: [R—Ar—(COOH)2]x[Ar—(COOH)3]2-xM32+  (I) is provided where M is Mn, Cu, Co, Fe, Zn, Cd, Ni, or Pt; R is a bromine, nitro, a primary amine, C1-C4 alkyl secondary amine, C1-C4 alkyl oxy, Br—(C1-C4 alkyl), NO2—(C1-C4 alkyl), a mercaptan, and reaction products of any of the aforementioned with acyl chlorides of the formulas: CH3(CH2)mC(O)Cl, or CH3(CH(C1-C4 alkyl)CH2)mC(O)Cl, or CH3(CH2)m-Ph-(CH2)pC(O)Cl, where Ph is a C6 phenyl or C6 phenyl with one or more hydrogens replaced with F, C1-C4 fluoroalkyl, or C1-C4 perfluoroalkyl; m is independently in each occurrence an integer of 0 to 12 inclusive; p is an integer of 0 to 36 inclusive, to form an amide, a thioamide, or an ester; Ar is a 1,3,5-modified phenyl, and 1.4>x>0. A process of synthesis thereof and the use to chemically modify a gaseous reactant are also provided.