Rational design of a bifunctional, Two-Fold interpenetrated ZnII-Metal–Organic framework for selective adsorption of CO2 and efficient aqueous phase sensing of 2,4,6-Trinitrophenol

Abstract

A bifunctional, microporous ZnII metal–organic framework, [Zn2 (NH2BDC)2 (dpNDI)]n (MOF1) (where, NH2BDC=2-aminoterephthalic acid, dpNDI=N,N’-di(4-pyridyl)-1,4,5,8-naphthalenediimide) has been synthesized solvothermally. MOF1 shows an interesting two-fold interpenetrated, 3D pillar-layered framework structure composed of two types of 1D channels with dimensions of approximately 2.99V3.58 a and 4.58V5.38 a decorated with pendent @NH2 groups. Owing to the presence of a basic functionalized pore surface, MOF1 exhibits selective adsorption of CO2 with high value of heat of adsorption (Qst=46.5 kJmol@1 ) which is further supported by theoretically calculated binding energy of 48.4 kJmol@1 . Interestingly, the value of Qst observed for MOF1 is about 10 kJmol@1 higher than that of analogues MOF with the benzene-1,4-dicarboxylic acid (BDC) ligand, which establishes the critical role of the @NH2 group for CO2 capture. Moreover, MOF1 exhibits highly selective and sensitive sensing of the nitroaromatic compound (NAC), 2,4,6-trinitrophenol (TNP) over other competing NACs through a luminescence quenching mechanism. The observed selectivity for TNP over other nitrophenols has been correlated to stronger hydrogen bonding interaction of TNP with the basic @NH2 group of MOF1, which is revealed from DFT calculations. To the best of our knowledge, MOF1 is the first example of an interpenetrated ZnII-MOF exhibiting selective adsorption of CO2 as well as efficient aqueous-phase sensing of TNP; investigated through combined experimental and theoretical studies.