Catalytic C–H Bond Activation and Knoevenagel Condensation Using Pyridine-2,3-Dicarboxylate-Based Metal–Organic Frameworks

Three 1D coordination
polymers (CPs) [M­(pdca)­(H2O)2]n (M = Zn, Cd, and Co; 1–3), and a 3D coordination
framework {[(CH3)2NH2]­[CuK­(2,3-pdca)­(pa)­(NO3)2]}n (4) (2,3-pdca
= pyridine-2,3-dicarboxylate and pa = picolinic acid), have been synthesized
adopting a solvothermal reaction strategy. The CPs have been thoroughly
characterized using various spectral techniques, that is, elemental
analyses, FT-IR, TGA, DSC, UV/vis, and luminescence. Structural information
on 1–4 was obtained by PXRD and X-ray single-crystal
analyses, whereas morphological insights were attained through FESEM,
AFM, EDX, HRTEM, and BET surface area analyses. Roughness parameters
were calculated from AFM analysis, whereas dimensions of small domains
and interplanar spacing were defined with the aid of HRTEM. CPs 1–3 are 1D isostructural networks, whereas 4 is a 3D framework. Moreover, 1–4 display moderate
luminescence at rt. In addition, 1–4 have been
applied as economic and efficient porous catalysts for the Knoevenagel
condensation reaction and C–H bond activation under mild conditions
with good yields (95–98 and 97–99%), respectively. Notably, 1–3 can be reused up to seven cycles, whereas 4 can be reused up to five catalytic cycles with retained
catalytic efficiency. Relative catalytic efficacy toward the Knoevenagel
condensation reaction follows in the order 2 > 1 > 3 > 4, whereas 2 > 4 > 1 > 3 for
C–H
activation. The present result demonstrates synthetic, structural,
optical, morphological, and catalytic aspects of 1–4.