Porphyrin Catecholate Iron-Based Metal-Organic Framework for Efficient Visible Light-Promoted One-Pot Tandem C-C Couplings

Introduction of metal-organic frameworks (MOFs) beyond metal-carboxylate series and their applications are still challenging. An innovative porous porphyrin catecholate iron-based MOF (PorphCat-Fe) with a Brunauer-Emmett-Teller (BET) surface area of 700 m2 g-1 has been designed and synthesized through solvothermal self-assembling porphyrin catecholate linkers and iron(II) chloride as a cheap and earth-abundant node precursor. The structure was then evaluated with various techniques and utilized as an efficient and stable heterogeneous material for domino one-pot selective benzyl alcohol oxidation/Knoevenagel condensation reaction under visible LED light irradiation. The photocatalytic performance was remarkably improved as compared to individual components, affording excellent product yields (91%) with almost quantitative transformation of benzyl alcohol. The combination of Fe(III)-Lewis acidic sites and free-base porphyrin photosensitizers within the porous solid material make PorphCat-Fe able to show superior catalytic activity for this transformation. In addition, the MOF can easily accommodate the starting materials inside its mesopores and, thereby, make them easily accessible to active sites. This is an unusual example of an all-in-one noble metal-free bio-inspired supramolecular chemistry for an advanced organic transformation without the need of any chemical additive or further structural modification using only visible LED light conservation.
This work was supported by the Iran National Science Foundation (INSF) (Project Number: 98024397). We also thank Monika Kucerakova for assistance with PXRD experiments. The authors wish to acknowledge the University of Zabol (Grant numbers: IR-UOZ-GR-9381). This publication was supported by RUDN University Strategic Academic Leadership Program (R.L.).