Abstract Nitric acid (HNO3) vapor is highly corrosive and hazardous yet developing room-temperature chemiresistive sensors for its sensitive and selective detection remains challenging. Herein, we report a mixed-ligand copper iodide cluster, Cu2I2(P-(m-Tol)3)2(4VP)2, as a molecularly engineered sensing material for HNO3 vapor detection. The incorporation of complementary phosphine and pyridine ligands simultaneously enhances the structural stability of the copper(I) iodide framework and provides accessible recognition sites for acidic gas molecules. The chemiresistive sensor exhibits excellent HNO3 sensing performance at room temperature, delivering a high response of 925% toward 100 ppm of HNO3, low theoretical limit of detection of 235 ppb and limit of quantitation of 784 ppb, rapid response/recovery times of 13/8.8 s, as well as outstanding selectivity, humidity tolerance and cycling stability. Density functional theory calculations reveal that HNO3 are anchored on the cluster surface via cooperative dual-site adsorption involving an O–H···I hydrogen-bond-like interaction and an O···H–C interaction with the 4VP ligand. The cooperative adsorption mode induces interfacial charge redistribution, accompanied by electron transfer from the n-type cluster to HNO3 molecules, thereby modulating the electrical resistance. This work establishes a molecular-level relationship between ligand regulation, acidic gas recognition, and chemiresistive response, providing a rational strategy for cluster-based sensors for highly corrosive gas detection.
The precise modulation of the electronic structure in bimetallic metal–organic frameworks (BMOFs), achieved by altering their metal nodes, critically governs their photocatalytic performance. However, how altering the metal nodes in BMOFs regulates the inherent structure–performance relationship remains unclear. Here, a series of CoM-HHTP with similar crystal structures (M = Ni, Cu, and Fe; HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) were integrated with CdS nanorods, yielding CdS@CoM-HHTP heterojunctions, which exhibited tunable performance in photocatalytic benzylamine coupling and hydrogen evolution. Among them, CdS@Co0.75Fe0.25-HHTP exhibits the best catalytic performance, with a hydrogen evolution rate of 55.29 mmol g–1 h–1 and a benzylamine conversion rate of 63.76%. The experimental results show that substitution of the second metal (M = Ni, Cu, and Fe) effectively modulates the electronic configuration of Co and significantly regulates the ability of BMOFs to extract photogenerated electrons from CdS, thereby enabling tunable photocatalytic activity. This study substantiates that modulation of the secondary metal node is pivotal for achieving synergistic regulation of both the active-site electronic structure and the photocatalytic performance.
Examples of planar hexacoordinate molecular systems are scarce in the literature, particularly for the covalently bonded planar hexacoordinate group 14 elements. In the previously reported such systems, three bonds were covalent in nature, and the remaining three bonds were predominantly supported by electrostatic interactions. Here, we report that the global minimum of the 20-valence electronic XBe6Au62+ (X = Si, Ge) clusters has a D6h-symmetric star-like structure featuring planar hexacoordinate silicon and germanium (phX) atoms, which are strongly covalently bonded to the Be6 ring through three σ and one π-electron-sharing bonds. Additionally, electrostatic interactions also contribute considerably to the stabilization of the phX clusters. These clusters show high stability against dissociation and kinetic stability against distortion from planarity. The stability of phX species can be attributed to the electronic stabilization (2π + 6σ double aromaticity) and the optimal geometrical match between the planar X center and the peripheral Be6Au6 ring, making them promising candidates for experimental realization. We have further explored the possibility of blocking the reactivity of phX by [10]cycloparaphenylenes ([10]CPP), forming a viable host–guest complex while maintaining the novel electronic and structural integrity of phX motifs.
MXenes are two-dimensional nanomaterials with strong near-infrared (NIR) absorption and high photothermal conversion capability. However, their catalytic applications in the NIR region have been constrained by insufficient catalytic activity and the intrinsically low photon energy in this spectral range. To break this bottleneck, (3-aminopropyl)triethoxysilane is used to covalently modify titanium carbide MXene (Ti3C2TX) to obtain aminated NH2–Ti3C2, which is further electrostatically assembled with catalytically active transition-metal-substituted Keggin-type polyoxometalates (POMs), affording POMs@NH2–Ti3C2 composites. Under NIR irradiation, these catalysts generate the localized photothermal effect around the catalytic centers, efficiently driving the oxidation of tetrahydroquinoline derivatives. The precise synergy between photothermal and catalytic centers enables near-unity product selectivity, suppressing byproduct formation and thus minimizing organic solvent waste. Under photothermal conditions, the system achieves a turnover frequency as high as 154.3 h–1, far surpassing that of conventional external heating at the same temperature and outperforming most non-noble-metal and even noble-metal catalysts. This work not only expands the photothermal applications of POM-based composites but also demonstrates a feasible strategy for driving green catalytic transformations using light as a remote heat source, offering new insights into the synergistic development of energy-input saving and separation-process minimization for fine chemical synthesis.
Interstitial hydrides can modulate the electronic and geometric structures of atomically precise metal nanoclusters (NCs). Direct crystallographic localization of hydrides in heavy-metal nanoclusters remains challenging by single-crystal X-ray diffraction (SCXRD). Here, dithiophosphate-to-diselenophosphate ligand exchange produced [Ni(H)Ag19{Se2P(OiPr)2}12] (1x) and [NiAg20{Se2P(OiPr)2}12] (2). The ligand exchange enabled the growth of high-quality single crystals suitable for neutron diffraction. The neutron structure of 1x (1o) directly locates the hydride in an interstitial μ4-NiAg3 cavity, providing the first direct neutron-crystallographic localization of a Ni–H motif in a superatomic nanocluster. The result supports the metallic-hydrogen description for a first-row-transition-metal-centered superatom. Comparison with the hydride-free analogue shows hydride-induced distortion and expansion of the Ag12 core together with changes in optical response. These findings provide an experimental structural benchmark for Ni-centered hydride superatoms and establish neutron diffraction as a direct probe of interstitial hydrogen in heavy-metal nanoclusters.
