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Metal–organic frameworks (MOFs) with π-electronic conjugated systems have garnered considerable attention, enabling third-order nonlinear optics. However, their nonlinear optical (NLO) properties pose challenges, including photogenerated carrier formation and low charge separation, which require urgent improvement. In this study, zero-dimensional Ti3C2 MXene quantum dots (Ti3C2 QD) and two-dimensional V2C MXene derived porphyrinic MOFs (V2C PMOF) are assembled into the heterostructure, denoted as Ti3C2 QD/V2C PMOF, which is fully characterized by crystallographic, spectroscopic, and microscopic methods. It is worth noting that the parental features are easily inherited from the hard template, thus tailoring MOFs with controlled dimensional growth. The Ti3C2 QD/V2C PMOF heterostructure shows optimized reverse saturable absorption (RSA) compared to individual components, under irradiation with both nanosecond (ns) pulses at 532 nm and femtosecond (fs) pulses at 800 nm. The enhancement of the NLO response is mainly attributed to the exceptional interfacial electron transfer capabilities, corroborated by steady-state photoluminescence, X-ray photoelectron spectroscopy, and theoretical calculations. These discoveries not only provide invaluable insights into the undeveloped vanadium-based MOF for future practical NLO applications but also establish a reference for the development of MOF-based materials via the guest–host strategy. [ABSTRACT FROM AUTHOR]

We describe herein a stepwise approach to accomplish the covalent linkage of fullerenes C60 and C70 to few-layer Ti3C2Tx MXene, for the first time. The preparation process involves the functionalization of Ti3C2Tx with 4-benzaldehyde diazonium salt followed by 1,3-dipolar cycloaddition to the double bonds of C60 and C70 in the presence of aldehyde-decorated nanosheets and excess N-methylglycine. The synthesized nanohybrids, named C60-MXene and C70-MXene, respectively, were comprehensively characterized by crystallographic, spectroscopic, thermal, and electron microscopic means. UV-vis-NIR absorption measurements reveal a decrease in the electron density of the nanosheets upon the incorporation of fullerenes, indicating the occurrence of intercomponent electronic interactions. Z-scan studies demonstrate that C60-MXene and C70-MXene show an excellent nonlinear absorption performance, that is, an enhanced optical limiting (OL) effect compared to their individual components, under the irradiation of both nanosecond (ns) pulses at 532 nm and femtosecond (fs) pulses at 800 nm. The effective electron transfer behavior from Ti3C2Tx to the grafted fullerenes under photoexcitation should be responsible for the observed OL enhancement. Our findings showcase that C60-MXene and C70-MXene nanohybrids are promising OL candidates across spectral regions and temporal domains, and that the proposed strategy of interfacing fullerenes with Ti3C2Txvia covalent bonding provides a paradigm for engineering high-performance nonlinear optical (NLO) materials using covalently linked binary nanohybrids based on MXene nanosheets. [ABSTRACT FROM AUTHOR]

Competitive optical limiters that can protect sensitive instruments and eyes from intense ultrafast laser irradiation across a wide spectral range are key to the expanding use of ultrafast pulsed lasers. Herein, for the first time, we report a facile and covalent diazonium approach to the functionalization of tin disulfide (SnS2) nanosheets with organic porphyrins, in the pursuit of excellent optical limiting performance. The SnS2–porphyrin nanohybrid (SnS2–Por) was assembled by reacting SnS2 nanosheets with a porphyrin diazonium salt that had been chemically activated with the reducing agent potassium iodide. In the femtosecond (fs) regime, the SnS2–Por nanohybrid shows significantly enhanced reverse saturable absorption and effective nonlinear optical absorption coefficients, which are 2.8- to 5.8-fold higher than those of pristine SnS2 nanosheets under identical laser irradiation; the optical limiting thresholds of the SnS2–Por nanohybrid are 2736 μJ cm−2 at 800 nm and 1650 μJ cm−2 at 515 nm, which outstrip most reported fs-active NLO materials (e.g., WS2, InSe, carbon nanodots, and graphene oxide), suggesting promising applications in ultrafast optical limiting. A dynamic energy model was proposed to demonstrate the relationship between charge transfer in the excited states of the SnS2–Por nanohybrid and the nonlinear optical performance. This work not only offers a paradigm for facile covalent functionalization of SnS2, but it also sheds new light on the construction of nanohybrids with excellent optical limiting performance. [ABSTRACT FROM AUTHOR]

Covalent functionalization of two-dimensional transition-metal dichalcogenides (TMDs) enables the manipulation of optical and electronic properties in hybrid structures and enhances their versatility for various potential applications. Herein, exfoliated few-layer TiS2 is covalently functionalized by tetraphenylporphyrin (TPP) diazonium salts for the first time. The newly synthesized TPP–TiS2 nanohybrid is fully characterized by crystallographic, spectroscopic, microscopic, and thermal methods. Its excited-state behavior is investigated by steady-state and time-resolved photoluminescence measurements, indicating the formation of a donor–acceptor (D–A) system, in which an efficient energy transfer from the photoexcited TPP to TiS2 layer is expected to occur. Z-scan studies show a significantly enhanced saturation absorption (SA) of the TPP–TiS2 nanohybrid in comparison with that of pure TiS2 at 532 nm under nanosecond (ns) pulses, though TPP exhibits typical reverse saturation absorption (RSA). The reinforced band-filling effect due to intrahybrid energy transfer may play an important role in determining the nonlinear absorption performance of TPP–TiS2. Our results shed new light on the preparation of a TiS2-derived nanohybrid by constructing a suitable D–A binary system, which is important in developing photonic devices such as mode-locked or Q-switched lasers. [ABSTRACT FROM AUTHOR]