RESUMEN
This study used the tert-butylcalix[6]arene (TBC[6]) as the ligand and successfully synthesized six TBC[6]-stabilized titanium-oxo clusters (TOCs) by the one-step solvothermal reaction. These six compounds were [Ti4O2(TBC[6])2] (Ti4), {Ti2(TBC[6])(EtO)2(SaH2)2} (Ti2-SA, H2Sa = squaric acid), {Ti2(TBC[6])2(EtO)2(Oa)} (Ti2-OA, H2Oa = oxalic acid), [H2Ti4(TBC[6])(BA)2(EtO)10] (Ti4-BA, HBA = benzoic acid), [Ti6O2(TBC[6])(BA)4(OiPr)10] (Ti6-BA), and [Ti8(TBC[6])2(Sal)4(EtO)16] (Ti8-Sal, H2Sal = salicylic acid). These clusters contain one or two TBC[6] ligands, with the biconical or monoconical configuration, greatly increasing the variety of TOCs it could support. The introduction of auxiliary carboxylic ligands can further stimulate the growth of structures, with the cluster core gradually increased from {Ti-TBC[6]-Ti} to {Ti2-TBC[6]-Ti2}, to {Ti3-TBC[6]-Ti3}, and finally to {Ti3-TBC[6]-Ti2-TBC[6]-Ti3} with 3.1 nm length. Structural regulation may affect their solution stability, absorption spectra, and photocurrent response. The study of catalytic activities shows that these clusters can be used as recyclable heterogeneous photocatalysts for the oxidation of sulfide to sulfoxide. The catalytic efficiency of the TBC[6]-Tix system is closely related to the cluster structure, and the exposure of the Ti site on the catalyst surface can significantly enhance the catalytic activity of the clusters.
RESUMEN
A large polymolybdate-templated {Ag49Mo16} cluster protected by six thiacalix[4]arene (TC4A) molecules was synthesized by a one-pot solvothermal reaction. Structural analysis shows that the {Ag49Mo16} is assembled by inserting a [Mo6O22]8- cluster into a [Ag49Mo10@(TC4A)6] cage, representing the first polyoxometalate-templated Ag cluster protected by calixarene macrocyclic ligands. The solution stability and photoelectric properties of {Ag49Mo16} are discussed. Furthermore, this POM-templated Ag nanocluster realized electrocatalytic CO2 reduction applications, and 44.75% CO faradaic efficiency (FE) was obtained at a voltage of -0.8 V (vs. RHE).
RESUMEN
Skillfully engineering surface ligands at specific sites within robust clusters presents both a formidable challenge and a captivating opportunity. Herein we unveil an unprecedented titanium-oxo cluster: a calix[8]arene-stabilized metallamacrocycle (Ti16L4), uniquely crafted through the fusion of four "core-shell" {Ti4@(TBC[8])(L)} subunits with four oxalate moieties. Notably, this cluster showcases an exceptional level of chemical stability, retaining its crystalline integrity even when immersed in highly concentrated acid (1 M HNO3) and alkali (20 M NaOH). The macrocycle's surface unveils four specific, customizable µ2-bridging sites, primed to accommodate diverse carboxylate ligands. This adaptability is highlighted through deliberate modifications achieved by alternating crystal soaking in alkali and carboxylic acid solutions. Furthermore, Ti16L4 macrocycles autonomously self-assemble into one-dimensional nanotubes, which subsequently organize into three distinct solid phases, contingent upon the specific nature of the four µ2-bridging ligands. Notably, the Ti16L4 exhibit a remarkable capacity for photocatalytic activity in selectively reducing CO2 to CO. Exploiting the macrocycle's modifiable shell yields a significant boost in performance, achieving an exceptional maximum CO release rate of 4.047 ± 0.243 mmol g-1 h-1. This study serves as a striking testament to the latent potential of precision-guided surface ligand manipulation within robust clusters, while also underpinning a platform for producing microporous materials endowed with a myriad of surface functionalities.