Research On Nanocatalyst Construction Of Metal-Organic Framework Materials And Its Catalytic Hydrogenation Of Quinoline

Heterocyclic compounds,especially nitrogen heterocycles,are the most important class of compounds in the pharmaceutical and agrochemical industries,with heterocycles comprising around 60%of all drug substances.Tetrahydroquinoline ring is a very common structural motif,which exists in many natural products with biological activity and pharmacologically related therapeutic drugs.At present,the simple and effective method to produce tetrahydroquinoline ring is selective hydrogenation of quinoline and its derivatives.In this paper,the selective hydrogenation of quinoline and its derivatives is studied.Based on metal-organic framework material with zirconium nodes and 2,2’-bipyridine-5,5’-dicarboxylic acid ligand(known as UiO-67N)as the carrier,we design and construct two different types of nanocatalysts(UiO-67N@Pt@UiO-67N and UiO-67N-Mn(CO)3Br).The relationship between the structure,composition and properties of catalysts under different reaction conditions is studied.The summary results of specific research are as follows:(1)we construct platinum nanoparticles sandwiched in an inner core and an outer shell composed of a metal-organic framework synthesized by zirconium chloride and 2,2’-bipyridine-5,5’-dicarboxylic acid(UiO-67N).Different sandwich structures with the shell thickness of 11 nm,28 nm and 42 nm are precisely prepared.The sandwich structure catalyst can catalyze hydrogenation of quinoline to 1,2,3,4-tetrahydroquinoline at room temperature and 2 MPa hydrogen,the catalytic activity increases significantly with the decrease of the shell thickness.When quinoline transforms completely,the selectivity of 1,2,3,4-tetrahydroquinoline(>99%).High conversion and product selection can also be achieved under mild conditions when quinoline derivatives are used as substrates.Importantly,the activity and selectivity of sandwich catalysts can be maintained through continuous cyclic experiments,showing good stability.X-ray diffraction and Fourier transform infrared spectroscopy analyses show that the excellent properties of sandwich structure are mainly due to the electron transfer effect between UiO-67N and Pt nanoparticles and the strong interfacial interaction between UiO-67N and quinoline.(2)Using UiO-67N as the carrier and pentacarbonyl manganese bromide as the precursor,UiO-67N-Mn(CO)3Br catalyst can be obtained by grafting the single metal site Mn onto the bipyridine ligand.Under given conditions(60℃,2 MPa H2 and 18 h;hydrogen bromide solution with acetic acid as additive),the conversion rate of quinoline hydrogenation catalyzed by UiO-67N-Mn(CO)3Br is 96%and the selectivity of 5,6,7,8-tetrahydroquinoline is 97%.However,the selectivity of 1,2,3,4-tetrahydroquinoline with pentacarbonyl manganese bromide as homogeneous catalyst is over 99%.Preliminary analysis suggests that the difference in catalytic selectivity is mainly because the additive can stimulate the activity of UiO-67N-Mn(CO)3Br and change the adsorption mode of quinoline in UiO-67N channels,thus contributing to the formation of 5,6,7,8-tetrahydroquinoline.