Abstract:Molecularly imprinting polymers (MIPs) have been extensively applied in chromatography for the separation of chiral drugs. In this review, we mainly summarize recent developments of various MIPs used as chiral stationary phases (CSPs) in high performance liquid chromatography (HPLC), capillary electrochromatography (CEC), and supercritical fluid chromatography (SFC). Among them, HPLC has the advantages of straightforward operation and high selectivity. However, the low separation efficiency, due to slow interaction kinetics and heavy peak broadening, is the main challenge for the application of MIPs in HPLC. On the other hand, CEC possesses both the high selectivity of HPLC and the high efficiency of capillary electrophoresis. In CEC, electroosmotic flow is formed across the entire column and reduces the heavy peak broadening observed in HPLC mode. SFC can modify the low interaction kinetics in HPLC when supercritical fluids are utilized as mobile phases. If SFC and MIP-based CSPs can be well combined, better separation performance can be achieved. Particles, monoliths and membrane are typical formats of MIPs. Traditional MIP particles produced by bulk polymerization have been replaced by MIP particles by surface imprinting technology, which are highly consistent in size and shape. Monolithic MIPs are prepared by in situ method in a column, greatly shortening the pre-preparation time. Some novel materials, such as magnetic nanoparticles, are integrated into the MIPs to enhance the controllability and efficiency of the polymerization. This review will be helpful to guide the preparation, development, and application of MIPs in chromatographic and electrophoretic enantioseparation.

Broadening of inner molecular orbitals upon adsorption can predict chemoselectivity of metal catalysts.

No abstract

Interfaces between organic molecules and inorganic solids adapt a prominent role in fundamental science, catalysis, molecular sensors, and molecular electronics. The molecular adsorption geometry, which is dictated by the strength of lateral and vertical interactions, determines the electronic structure of the molecule/substrate system. In this study, we investigate the binding properties of benzene on the noble metal surfaces Au(111), Ag(111), and Cu(111), respectively, using temperature-programmed desorption and first-principles calculations that account for non-locality of both electronic exchange and correlation effects. In the monolayer regime, we observed for all three systems a decrease of the binding energy with increasing coverage due to repulsive adsorbate/adsorbate interactions. Although the electronic properties of the noble metal surfaces are rather different, the binding strength of benzene on these surfaces is equal within the experimental error (accuracy of 0.05 eV), in excellent agreement with our calculations. This points toward the existence of a universal trend for the binding energy of aromatic molecules resulting from a subtle balance between Pauli repulsion and many-body van der Waals attraction.

Understanding the binding mechanism for aromatic molecules on transition-metal surfaces in atomic scale is a major challenge in designing functional interfaces for to (opto)electronic devices. Here, we employ the state-of-the-art many-body dispersion (MBD) approach, coupled with density functional theory methods, to study the interactions of benzene with low-index coinage metal surfaces. The many-body effects contribute mostly to the (111) surface, and leastly to the (110) surface. This corresponds to the same sequence of planar atomic density of face-centered-cubic lattices, i.e., (111) > (100) > (110). The binding energy for benzene/Au(110) is even stronger than that for benzene/Ag(110), due to a larger broadening of molecular orbitals in the former case. On the other hand, our calculations show almost identical binding energies for benzene on Ag(111) and Au(111), which contradicts the classic d-band center theory that could well predict the trend in chemisorption energies for various small molecules on a number of metal surfaces. Our results provide important insight into the benchmark adsorption systems with opener surfaces, which could help in designing more complex functional interfaces.