Abstract:Flanked –NH2 functionality, polar carbonyl moiety and intrinsically unsaturated [Zn2(CO2)2(ATz)4] center‐decked micropores in an ultra‐robust metal‐organic framework (MOF) are reported, assembled from bent dicarboxylate and triazole (ATz) ligand. The MOF serves as one‐of‐a‐kind tandem Hantzsch condensation catalyst to yield a multitude of 1,4‐dihydropyridines (1,4‐DHPs) with low catalyst loading, short reaction duration at moderate temperature. Importantly, the MOF is used in the synthesis of six 1,4‐DHP‐based therapeutic molecules in >95% conversion, which are characterized in purest form via X‐ray crystallography besides other spectroscopic analyses. Apart from gram‐scale production of ethidine molecule at 40 °C in just 30 min, oxodipine drug is first‐time synthesized by any framework‐based catalyst. This mixed‐ligand MOF further demonstrates highly recyclable Friedel–Crafts (FC) alkylation of indole and β‐nitrostyrene and covers twenty electronically diverse substrates under relatively green conditions. Strikingly, larger‐sized substrates can't diffuse inside the micropores and exemplifies rarest shape‐reliant C‒C coupling reaction. Contrary to conventional Lewis‐acid activation, the maximum contribution from hydrogen‐bonding site promotes both tandem multi‐component and FC reactions, as comprehensively supported from control experiments, analyte‐induced emission articulation, inferior activity of task‐specific site‐truncated isoskeletal MOF, and density functional theory results. This work provides a major advancement on unconventional heterogeneous catalysis to produce valuable products.
