Porous Metalloporphyrinic Frameworks Constructed from Metal 5,10,15,20-Tetrakis(3,5-biscarboxylphenyl)porphyrin for Highly Efficient and Selective Catalytic Oxidation of Alkylbenzenes

We incorporate metal 5,10,15,20-tetrakis­(3,5-biscarboxylphenyl)­porphyrin
(M-H8OCPP), for the first time, into porous metal–organic
frameworks. The self-assembled porous metalloporphyrinic frameworks
[Mn5Cl2(MnCl-OCPP)­(DMF)4(H2O)4]·2DMF·8CH3COOH·14H2O (ZJU-18; ZJU = Zhejiang University), [Mn5Cl2(Ni-OCPP)­(H2O)8]·7DMF­·6CH3COOH·11H2O (ZJU-19), and [Cd5Cl2(MnCl-OCPP)­(H2O)6]·13DMF·2CH3COOH·9H2O (ZJU-20) are isostructural as revealed
by their single X-ray crystal structures. The metalloporphyrin octacarboxylates
(M-OCPP) (M = MnIIICl for ZJU-18 and ZJU-20, M = NiII for ZJU-19) are bridged by binuclear and trinuclear metal
carboxylate secondary building units to form a 3-periodic, binodal,
edge-transitive net with Reticular Chemistry Structure Resource symbol tbo with pore windows of about 11.5 Å and pore cages
about 21.3 Å in diameter. The porous nature of these metalloporphyrinic
frameworks is further established by sorption studies in which different
substrates such as ethanol, acetonitrile, acetone, cyclohexane, benzene,
toluene, ethylbenzene, and acetophenone can readily have access to
the pores. Their catalytic activities for the oxidation of alkylbenzenes
were examined at 65 °C using tert-butyl hydroperoxide
as the oxidant. The results indicate that ZJU-18 is much superior
to ZJU-19, ZJU-20, and homogeneous molecular MnCl-Me8OCPP,
exhibiting highly efficient and selective oxidation of ethylbenzene
to acetophenone in quantitative >99% yield and a turnover number
of
8076 after 48 h.