Interfacial P-band Intermediate State(PBIS)-Mediated Electron And Proton Transfer For Catalytic Hydrogenation

Chemical reaction is the process of the sharing and redistribution of electron and proton transfer on the interface.Therefore,only understand the nature and movement laws of electrons and protons of enzyme-like catalytic system accurately,can we effectively guide the construction of electron and proton transfer channels,realize the preparation of high-performance catalysts,and solve the current environmental and energy problems.Based on the research achievements of our group in the field of nanocluster luminescence,that the luminescence center of nanoclusters with enzyme-like structures is independent of metal nucleus,but comes from the new interface state PBIS with lower overall energy level induced by overlapping of p-orbitals of heteroatoms（O,N,S,B,etc.）.PBIS have high energy delocalized electrons andπ→π^*characteristic orbital,which are regulated by proton transfer.Thus,PBIS provides a new path for interfacial electron and proton transfer.Considering the similar structural characteristics of nanocatalytic interface and nanoclusters,PBIS theory provides a new perspective and research idea for studying electron and proton motion in the catalytic process.In this study,the novel PBIS theory was applied to nanocatalysis.By means of steady and transient-state spectroscopy and control experiment,the effects of PBIS-mediated electron and proton transfer on the catalytic mechanism ofα,β-unsaturated aldehyde（UAL）selective hydrogenation and 4-nitrophenol（4-NP）reduction were systematically investigated,aiming to reveal the nature of the role of electrons and protons in enzyme-like systems,and to guide the design and synthesis of high-efficiency hydrogenation catalysts.It mainly includes the following two aspects of research work:（1）To explore the regulation of PBIS-mediated electron transfer in UAL selective hydrogenation reaction.Firstly,by studying the enzyme-like catalytic process in which alkali promoted the conversion and selectivity of UAL hydrogenation simultaneously,the presence of PBIS induced by interface OH on the substrate interface and catalyst interface was confirmed.The PBIS,on the one hand,provided low-energyπ-orbital bonding orbital（Q_n）and higher-energyπ^*anti-bonding orbital（Q_n^*）,which are new reaction channels for electron transfer.It reduces the reaction energy barrier and promotes the conversion rate.On the other hand,according to the symmetry matching principle,theπ-π^*orbitals of PBIS facilitate the highly selective by tuning the selective adsorption activation of substrates.Therefore,PBIS are the real active site for catalytic reaction,which are controlled by PBIS mediated electron transfer.Based on the above understanding of PBIS-regulated electron transfer in catalysis,through reconstruction of surface small molecule and regulation of interface OH interaction in the reduced transition metal oxide Ti O₂ and heteroatom-doped carbon systems,optimal PBIS are constructed,which guided and realized the preparation of alkali-free high efficiency catalysts.From a new perspective of PBIS,the research broke through the traditional metal-centered catalytic mechanism and catalyst preparation strategy,solved the bottleneck problem of the promotion of alkali in catalysis,reinterpreted the potential nature of SMSI and the role of heteroatoms,and providing reliable reference ideas and broader research perspective for the design of high-efficiency enzyme-like catalysts.（2）To explore the regulation of PBIS-mediated electron and proton transfer in the 4-NP reduction reaction.First of all,using traditional catalytic characterization techniques combined with spectroscopy,it was confirmed that the active site of 4-NP hydrogenation was not traditionally metal NPs,but the PBIS constructed by appropriate interface OH.After interacted with the substrate molecule,PBIS transformed into a new intermediate state PBIS.Because PBIS has high-energy delocalized electrons and specificπ-π^*characteristic orbitals,it provides a new transfer path for electron with a lower energy barrier,thereby changing the reaction route,and realizing the activation of the N=O bond,and promoting the hydrogenation reaction.Therefore,the catalytic reaction does not follow the classic metal-centered L-H mechanism,but PBIS-mediated electron and proton transfer process.Based on the determination of the PBIS-mediated catalytic reaction process,through isotopic effects and FTIR spectroscopy,it was confirmed that the rate-determining step of the catalytic reaction was the activation of H₂O.The hydrogen source came from H₂O instead of Na BH₄ as traditionally thought.Therefore,water-related interface state PBIS is the key channel for electron and proton transfer.Combined with ¹H spectrum,which tracked the chemical environment changes during the reaction,the PBIS-mediated proton transfer process is determined,that is,in the triangular configuration of the key intermediate H₃B-water-hydroxyl,if the O atom of the reactant 4-NP is involved,it is the four-center activated surface complex H₃B-water-hydroxy-4-NP,the multi-center intermediate generates a new interface state PBIS through the spatial overlap of the p orbitals of the B and O atoms,the coordinated transfer of electrons and protons are promoted as the Grotthus mechanism,which is observed in the proton-reduced[Fe Fe]-hydrogenase.Finally,different from traditional strategy of the design of catalyst,wich are centered on modifying the electronic state of the metal,with PBIS theory,bimetallic strategy was used to adjust the state of PBIS induced by interface OH,efficient 4-NP hydrogenation catalysts were prepared.The results show that bimetallic catalysts follow the same PBIS-mediated electron and proton transfer mechanism as mono-metallic catalysts.The larger k value of solvent(k _H2O/_D2O)in the bimetal,verified that the higher reactivity of bimetal comes from the regulation of PBIS significantly promoted the proton transfer process.At the same time,due to the high energy delocalized electrons,PBIS can affect the local electron density,which can regulate the aggregation of metal precursor and affect the particle size in the preparation of catalyst.The electronic properties of the bimetallic surface show that there is no direct electron transfer between metals at the bimetallic interface,but PBIS mediated electron transfer path.This work reveals the nature of the"synergistic effect"in bimetals from the perspective of PBIS,and confirms the decisive role of PBIS in the direction and path of electron transfer at the bimetal interface,as well as its broad application prospect in material synthesis science.Therefore,PBIS theory is practical and universal,and has an important role and great potential in the fields of nanocatalysis,material synthesis,and life medicine.