在自然界中，季节变换带来了树叶色彩的丰富变化，尤其是秋天的树叶变色现象，吸引了无数目光和科学探索。但在这背后，是一系列复杂的化学变化和色素分子结构的巧妙调整。本文将深入探讨秋天树叶变色的化学结构基础。

常用的密度泛函理论量子化学计算需要为交换相关泛函设置参数。电子间交换作用也就成为计算化学教学中经常提及的重要物理量。为了便于学生理解交换作用，以氦原子和碳原子为例，利用现有结构化学教材中的知识，本文阐释了交换作用与一般库仑作用的区别，为何交换作用源于泡利原理，以及如何通过交换作用理解洪特规则。

(2E, 6E)-4-methyl-2, 6-bis(pyridin-3-ylmethylene)cyclohexan-1-one (L₁) and 4-methyl-2, 6-bis[(E)-4-(pyridin-4-yl)benzylidene]cyclohexan-1-one (L₂) were synthesized and combined with isophthalic acid (H₂IP), then under solvothermal conditions, to react with transition metals achieving four novel metal organic frameworks (MOFs): [Zn(IP)(L₁)]_n (1), {[Cd(IP)(L₁)]·H₂O}_n (2), {[Co(IP)(L₁)]·H₂O}_n (3), and [Zn(IP)(L₂)(H₂O)]_n (4). MOFs 1-4 have been characterized by single-crystal X-ray diffraction, powder X-ray diffraction, thermogravimetry, and elemental analysis. Single-crystal X-ray diffraction shows that MOF 1 crystallizes in the monoclinic crystal system with space group P2₁/n, and MOFs 2-4 belong to the triclinic system with the P1 space group. 1-3 are 2D sheet structures, 2 and 3 have similar structural characters, whereas 4 is a 1D chain structure. Furthermore, 1-3 exhibited certain photocatalytic capability in the degradation of rhodamine B (RhB) and pararosaniline hydrochloride (PH). 4 could be used as a heterogeneous catalyst for the Knoevenagel reaction starting with benzaldehyde derivative and malononitrile. 4 could promote the reaction to achieve corresponding products in moderate yields within 3 h. Moreover, the catalyst exhibited recyclability for up to three cycles without significantly dropping its activity. A mechanism for MOF 4 catalyzed Knoevenagel condensation reaction of aromatic aldehyde and malononitrile has been initially proposed.

石墨相氮化碳(g-C₃N₄)在光催化制备过氧化氢(H₂O₂)领域有巨大潜力。然而，低的两电子氧还原活性严重限制了g-C₃N₄的光催化产H₂O₂效率。在这项研究中，我们通过两步煅烧法在KI晶体表面重新晶化传统g-C₃N₄材料，合成了钾掺杂的高晶化g-C₃N₄光催化剂(CN-K)。所制备的CN-K光催化材料具有更高的面间结晶度、更窄的禁带宽度和更小的颗粒尺寸(大约20到50纳米)。更重要的是，掺入的钾原子作为优异的催化位点可以增强O₂吸附和稳定*OOH中间体，从而提高钾掺杂高晶化g-C₃N₄光催化剂的两电子氧还原活性。其中CN-K(1:6)样品具有显著增强的光催化产H₂O₂速率(7.8 mmol·L^-1·h^-1)，且在420 nm下的表观量子效率为5.17%，光催化活性是传统块状g-C₃N₄样品的220倍。这项研究不仅揭示了杂原子提高g-C₃N₄光催化剂两电子氧还原活性的机理，而且为设计高效g-C₃N₄基光催化剂提供了新的见解。

5-(dimethylamino) isophthalic acid (H₂dia) and 1H-imidazole (mdz) were used as ligands to react with Zn(Ⅱ) or Cu(Ⅱ) metal salts to generate three new transition metal complexes [Zn(dia)(mdz)₂]·2H₂O (1), [Cu(dia)(mdz)₂ (DMF)] (2) and [Cu(dia)(mdz)₂]·H₂O (3). Their structures were characterized by single-crystal X-ray diffraction, elemental analysis, IR, thermogravimetric analyses, and Hirshfeld surface analyses. The results revealed that complexes 1 and 2 possess 1D linear chains, each four-coordinated Zn(Ⅱ) of 1 is located in the geometric center of the distorted tetrahedron, but the Cu(Ⅱ) metal center of 2 is five-coordinated and holds a triangular bipyramidal geometry. The zigzag 1D chain of complex 3 was obtained by changing the solvent in the synthesis, and the four-coordinated Cu(Ⅱ) ion is in the centre of the square planar. Results indicate that the geometries of metal centers and synthetic solvents have important effects on the structures of complexes. Abundant intermolecular hydrogen bonding plays an important role in the stability of their 3D supramolecular structures. Thermogravimetric analyses revealed that the complexes have good thermal stabilities. Solid fluorescence analyses showed that complex 1 had excellent fluorescence, but the fluorescence intensities of complexes 2 and 3 were much lower than those of ligands.

太阳能驱动的二氧化碳(CO₂)甲烷化反应不仅有助于减少多余的碳排放，而且是生产燃料的重要途径。层状金属双氢氧化物(layered double hydroxides，LDH)可以在高温还原气(H₂/Ar)氛围中还原，转化为金属负载于氧化物(MO)的催化剂。这些催化剂在CO₂加氢反应中作为优秀的光热催化剂被广泛应用。然而，有关LDH的层间阴离子类型如何影响CO₂甲烷化活性的研究还相对有限。本文研究了包含不同层间阴离子的镍(Ni)铝(Al) LDH前驱体，通过在H₂/Ar气氛中还原处理，制备了一系列Ni负载在氧化铝(Al₂O₃)上的MO催化剂，这些催化剂被命名为NiAl-x-MO (其中x代表CO₃、NO₃、Cl和SO₄，分别代表碳酸根、硝酸根、氯离子和硫酸根等阴离子)。其中，NiAl-CO₃-MO催化剂表现出50.1%的CO₂转化率，99.9%的甲烷(CH₄)选择性以及94.4 mmol∙g⁻¹∙h⁻¹的CH₄产出速率。与之相比，NiAl-Cl-MO和NiAl-SO₄-MO催化剂的CO₂甲烷化活性极低。H₂程序升温脱附(temperature programmed desorption with H₂，H₂-TPD)实验和密度泛函理论计算(density functional theory，DFT)结果表明，低CO₂转化率是由于残留的氯(Cl)或硫(S)与金属Ni形成的强配位键阻碍了H₂的吸附和活化。因此，在设计LDH衍生的催化剂，特别是用于氢化反应的Ni基催化剂时，应优先考虑层间阴离子在LDH中的重要作用。