Rational Design of a Bifunctional, Two‐Fold Interpenetrated Zn^II‐Metal–Organic Framework for Selective Adsorption of CO₂ and Efficient Aqueous Phase Sensing of 2,4,6‐Trinitrophenol

Abstract

Abstract A bifunctional, microporous Zn II metal–organic framework, [Zn 2 (NH 2 BDC) 2 (dpNDI)] n (MOF 1 ) (where, NH 2 BDC=2‐aminoterephthalic acid, dpNDI= N , N ′‐di(4‐pyridyl)‐1,4,5,8‐naphthalenediimide) has been synthesized solvothermally. MOF 1 shows an interesting two‐fold interpenetrated, 3D pillar‐layered framework structure composed of two types of 1D channels with dimensions of approximately 2.99×3.58 Å and 4.58×5.38 Å decorated with pendent −NH 2 groups. Owing to the presence of a basic functionalized pore surface, MOF 1 exhibits selective adsorption of CO 2 with high value of heat of adsorption ( Q st =46.5 kJ mol −1 ) which is further supported by theoretically calculated binding energy of 48.4 kJ mol −1 . Interestingly, the value of Q st observed for MOF 1 is about 10 kJ mol −1 higher than that of analogues MOF with the benzene‐1,4‐dicarboxylic acid (BDC) ligand, which establishes the critical role of the −NH 2 group for CO 2 capture. Moreover, MOF 1 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 −NH 2 group of MOF 1 , which is revealed from DFT calculations. To the best of our knowledge, MOF 1 is the first example of an interpenetrated Zn II ‐MOF exhibiting selective adsorption of CO 2 as well as efficient aqueous‐phase sensing of TNP; investigated through combined experimental and theoretical studies.