Paired-Pd(Ⅱ) centers embedded in HKUST-1 framework: Tuning the selectivity from dimethyl carbonate to dimethyl oxalate

CO oxidative coupling to dimethyl oxalate(DMO) is the most crucial step in coal to ethylene glycol. Pdbased supported catalysts have been verified effective for generating DMO, but concomitant generation of dimethyl carbonate(DMC) is always unavoidable. It is generally accepted that Pd(0) is the active species for producing DMO, while Pd(II) for DMC. However, density functional theory calculations have proposed that the selectivity to DMO or DMC highly depends on the space state of Pd species rather than its oxidative state. It is thus urgently desired to develop high-efficient catalysts with well-defined structure,and further to elucidate the structure-performance relationship. In this work, HKUST-1 with unique structure of paired-Cu(Ⅱ) centers was chosen as ideal support to construct the catalysts with respective paired-Pd(Ⅱ) centers and isolated-Pd(Ⅱ) centers via in situ Pd species doping. In despite of featuring Pdδ+(δ≈2) oxidation state, the synthesized paired-Pd(Ⅱ)/HKUST-1 catalyst still exhibited DMO as dominant product(90.8% of DMO selectivity). For isolated-Pd(Ⅱ)/HKUST-1 catalyst, however, the main product was DMC(84.8% of DMC selectivity). Based on catalyst characterizations, the structures of paired-Pd(Ⅱ) centers and isolated-Pd(Ⅱ) centers were determined. DMO was generated from the coupling of adjacent *COOCH;intermediates adsorbed on paired-Pd(Ⅱ) centers, while DMC was produced from the reaction between methyl nitrite and the *COOCH;intermediates formed on isolated-Pd(Ⅱ) centers. Current work is the first MOFs-based catalyst with well-defined structure being applied in CO oxidative coupling reaction, which not only sheds light on the structure-performance relationship, but also inspires the potential of using MOFs as tunable platform to design high-efficient catalysts in heterogeneous catalysis.

Theoretical Studies on Dehydrogenation Reactions in Mg2（BH4）2（NH2）2 Compounds

Borohydrides 是最近 hightlighted 同样未来的新材料由于他们为氢的高 gravimetric 能力存储。因此，为这些材料的进一步的开发理解内在的除氢作用机制是重要的。我们在场 Mg2 (BH4 ) 的除氢作用机制上的系统的理论调查 2 (NH2 ) 2 加重。我们发现除氢作用经由分子间的过程很可能发生，它与 intramolecular 过程的比较运动地并且热力学地是有利的。Mg2 (BH4 ) 的除氢作用 2 (NH2 ) 2 开始在 NH2 在 BH4 和 protic H 经由 hydridic H 的直接联合发生，由 MgH 的形成和 MgH H+N 的随后的离子的再结合列在后面。

Tunable CO_(2)enrichment on functionalized Au surface for enhanced CO_(2)electroreduction

Electrochemical conversion of carbon dioxide(CO_(2))to higher-value products provides a forward-looking way to solve the problems of environmental pollution and energy shortage.However,the low solubility of CO_(2)in aqueous electrolytes,sluggish kinetics,and low selectivity hamper the efficient conversion of CO_(2).Here,we report a Au-based hybrid nanomaterial by modifying Au nanoparticles(NPs)with the macrocyclic molecule cucurbit[6]uril(Au@CB[6]).Au@CB[6]displays the optimal selectivity of CO,with the highest CO Faraday efficiency(FECO)reaching 99.50%at−0.6 V vs.reversible hydrogen electrode(RHE).The partial current density of CO formed by Au@CB[6]increases dramatically,as 3.18 mA/cm2 at−0.6 V,which is more than ten times as that of oleylamine-coated Au NPs(Au@OAm,0.31 mA/cm2).Operando electrochemical measurement combined with density functional theory(DFT)calculations reveals that CB[6]can gather CO_(2)and lead the increased local CO_(2)concentration near metal interface,which realizes significantly enhanced electrochemical CO_(2)reduction reaction(CO_(2)RR)performance.

Simulation of the T-jump triggered unfolding and thermal unfolding vibrational spectroscopy related to polypeptides conformation fluctuation

We review in this article our recent simulation works on modeling peptide T-jump and thermal unfolding Fourier transform infrared spectroscopy(FTIR) and two-dimensional infrared(2DIR) spectra. The theoretical and computational techniques used,including Markov state model(MSM), integrated tempering sampling(ITS) and nonlinear exciton propagation(NEP), are first briefly introduced. The protocols for simulating the thermal unfolding as well as T-jump unfolding are then summarized in details. The simulated spectral features, such as the intensity and ellipticity, are demonstrated to agree well with the experimental observations.

Toward accurate and efficient dynamic computational strategy for heterogeneous catalysis:Temperature-dependent thermodynamics and kinetics for the chemisorbed on-surface CO

Computational tools on top of first principle calculations have played an indispensable role in revealing the molecular details,thermodynamics,and kinetics in catalytic reactions.Here we proposed a highly efficient dynamic strategy for the calculation of thermodynamic and kinetic properties in heterogeneous catalysis on the basis of efficient potential energy surface(PES)and MD simulations.Taking CO adsorbate on Ru(0001)surface as the illustrative model system,we demonstrated the PES-based MD can efficiently generate reliable two-dimensional potential-of-mean-force(PMF)surfaces in a wide range of temperatures,and thus temperature-dependent thermodynamic properties can be obtained in a comprehensive investigation on the whole PMF surface.Moreover,MD offers an effective way to describe the surface kinetics such as adsorbate on-surface movement,which goes beyond the most popular static approach based on free energy barrier and transition state theory(TST).We further revealed that the dynamic strategy significantly improves the predictions of both thermodynamic and kinetic properties as compared to the popular ideal statistic mechanics approaches such as harmonic analysis and TST.It is expected that this accurate yet efficient dynamic strategy can be powerful in understanding mechanisms and reactivity of a catalytic surface system,and further guides the rational design of heterogeneous catalysts.

Rational Preparation of Atomically Precise Non-Alkyl Tin-Oxo Clusters with Theoretical to Experimental Insights into Electrocatalytic CO_(2)Reduction Applications

Tin oxides(SnO_(2))have been widely utilized in electronics,nanolithography,and catalysis.As the atomically precise models of SnO_(2),tin-oxo clusters(TOCs)not only provide opportunities for mechanism studies,but they also extend potential applications through structural modulation.However,to date,most of the reported TOCs belong to alkyl organotin complexes,which are usually toxic to the human body and the active sites are difficult to expose for catalysis.

Accurate Description of Catalytic Selectivity:Challenges and Opportunities for the Development of Density Functional Approximations

An accurate description of catalytic selectivity poses an enormous challenge for theoretical simulations.Due to the absence of a well-defined benchmark set on the catalytic selectivity,the performance of even the widely used density functional approximations(DFAs)is yet to be validated.This work reports a test set based on the selective hydrogenation ofα,β-unsaturated aldehydes catalyzed by ruthenium(Ru)hydride complexes.Special attention is paid to benchmark the regioselectivity of aldehydes to either unsaturated alcohols or saturated aldehydes.Accurate reference data were calculated by the massive parallel implementation of the coupled-cluster single,double,and perturbative triple excitations[CCSD(T)]approach,based completely on set limits.Furthermore,we performed the microkinetic simulation based on the CCSD(T)energy profiles,serving the most direct criteria for the performance of DFAs on catalytic selectivity of hydrogenation reactions.Using this test set,we uncovered the intrinsic difficulty of semilocal and hybrid functionals for such a purpose.In the context of the XYG3-type double hybrid(xDH)framework,we showed that this particular challenge could be addressed by the top rung functionals only when the many-body nondynamic correlation effect was accounted for adequately.A recently proposed xDH,namely scsRPA,showed unprecedented accuracy with only 5%error on average.The predicted kinetic selectivity by scsRPA is in close agreement with the reference value,revealing a unique versatility of the top rung DFAs for a reliable description of catalytic selectivity of hydrogenation reactions.