Nanoengineering and Processing of Metal-Organic Framework Composites for Photonic Sensors

Project Information

PROMOFS

Grant agreement ID: 771575

DOI

10.3030/771575

Project closed

EC signature date 10 January 2018

Start date 1 April 2018

End date 30 September 2024

Funded under

• EXCELLENT SCIENCE - European Research Council (ERC)

Total cost

€ 2 431 911,00

EU contribution

€ 2 431 911,00

Coordinated by

THE CHANCELLOR, MASTERS AND SCHOLARS OF THE UNIVERSITY OF OXFORD
United Kingdom

Periodic Reporting for period 4 - PROMOFS (Nanoengineering and Processing of Metal-Organic Framework Composites for Photonic Sensors)

Reporting period: 2022-10-01 to 2024-09-30

Summary of the context and overall objectives of the project

The PROMOFS project lies is in the field of nanoporous materials engineering. It is focused on the discovery, characterisation, and application of metal-organic frameworks (MOFs) as an innovative platform to afford disruptive photonics sensing technology. Compared to the traditional materials (e.g. metal oxides and nitrides), MOFs offer several key advantages. The (hybrid) inorganic-organic structures of MOFs offer a huge prospect to tune the physical and chemical properties to enable the engineering of bespoke applications. Their 3D crystalline framework meant there is long-range periodicity, translating into continuous pathways to facilitate energy transfer and tuneable transport mechanisms. Significantly, the nanoscale pores within MOFs can be used as a vessel to host functional guests, in this context: to confine light-emitting guests for creating unconventional Guest@MOF photoluminescent composite systems fit for technological applications.

The overall objectives encompass:
(i) To establish facile processing of new Guest@MOF photonic materials and composite systems, utilising in-situ nanoscale confinement strategy combined with supramolecular processing strategies
(ii) To characterise photophysical and photochemical properties controlling the performance of Guest@MOF systems, and to understand fundamental mechanisms at the nanoscale
(iii) To employ ab initio computational modelling to gain deeper insights into host-guest interactions, and to predict structure-property relations informing the design of bespoke materials and Guest@MOF composite
(iv) To innovate in materials patterning technology for versatile materials-to-device manufacturing processes, employing 3D printing and electrospinning methodologies
(v) To apply Guest@MOF materials in nanoengineering of tuneable photonics sensors, paving the way to the engineering of mechanochromic, thermochromic, solvatochromic sensors
(vi) To quantify and enhance stability of Guest@MOF materials to yield long term stability aimed at practical applications

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The main results of the PROMOFS project are:

(1) Vastly tuneable fluorescent nanomaterials constructed from LG@MOFs have been designed and synthesised by harnessing the high-concentration reaction (HCR) method. We established HCR as the go to approach for engineering both two-dimensional (2D) and three-dimensional (3D) photoluminescent composites, exhibiting good material yields and reproducibility. Throughout this project, we pushed HCR to the limit and achieved a multitude of LG@MOF systems with unusual properties, ranging from electroluminescence and photochromism, to turn-on type mechanoluminescence and aggregation-induced emission. Further details can be found in the publications below.
• Confinement of luminescent guests in metal-organic frameworks: Understanding pathways from synthesis and multimodal characterization to potential applications of LG@MOF systems. Chem. Rev. 2022, 122, 10438-10483.
• Dye-encapsulated zeolitic imidazolate framework (ZIF-71) for fluorochromic sensing of pressure, temperature, and volatile solvents. ACS Appl. Mater. Interfaces 2020, 12, 37477-37488.
• Guest entrapment in metal-organic nanosheets for quantifiably tuneable luminescence. Adv. Funct. Mater. 2023, 33, 202214307.

(2) Multimodal and multiscale characterisation of novel LG@MOF composites, in conjunction with theoretical calculations, have enabled a deeper understanding of the local structure and functions of unconventional material systems. A major highlight is the successful implementation of nearfield infrared nanospectroscopy (nanoFTIR), reported for the first time in 2020, for probing the local chemical and physical behaviour of MOF crystals and LG@MOF composites. The 20-nm spatial resolution and in situ nanoscale probing capability of nanoFTIR made possible the precise study of the role of structural defects, mechanically induced bond breakage, and material homo/heterogeneity precisely at a single-crystal level. The difficult question of whether the guest is positioned inside or outside the MOF cage has finally been addressed via nearfield imaging.
• Near-field infrared nanospectroscopy reveals guest confinement in metal-organic framework single crystals. Nano Lett. 2020, 20, 7446−7454.
• Tunable fluorescein-encapsulated zeolitic imidazolate framework-8 nanoparticles for solid-state lighting. ACS Appl. Nano Mater. 2021, 4, 10321-10333.
• Mater. Today Nano 2022, 17, 100166.

(3) We demonstrated innovative processing of novel LG@MOF materials, thereby enabling different pathways for the shaping of fine crystalline powders of LG@MOFs into fluorescent films, mixed-matrix membranes, electrospun fibres, and monoliths. Varied techniques applicable here bodes well for future translation of LG@MOFs into practical devices.
• Dual‐guest functionalized zeolitic imidazolate framework‐8 for 3D printing white light‐emitting composites. Adv. Opt. Mater. 2020, 8, 1901912.
• Adv. Funct. Mater. 2023, 34, 202308062.
• ACS Appl. Mater. Interfaces 2024, 16, 56304-56315.

(4) LG@MOF materials with multi-stimuli response present a versatile platform for the engineering of bespoke optical sensors (VOCs, pressure, thermal, pH), solid-state light emitters and LEDs, and colour-changing photochromic devices pertinent to advanced implementations in a multitude of technological sectors.
• Unlocking diabetic acetone vapor detection by a portable metal‐organic framework‐based turn‐on optical sensor device. Adv. Sci. 2023, 11, 202305070.
• Resilient photoswitchable metal–organic frameworks for sunlight-induced on-demand photochromism in the solid state. Chem. Eng. J. 2023, 476, 146727.
• Adv. Opt. Mater. 2020, 8, 2000670.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

(1) We demonstrated new LG@MOF systems that can be tailored for ‘turn-on’ type optical sensing, which is a rare phenomenon in the field. The nanoconfinement of luminescent guest within the MOF cage facilitates the nanoscale partitioning and subsequent re-aggregation of encapsulated fluorophores to yield this turn-on effect. Under stress, the luminescent intensity rises, thus giving improved detection sensitivity because of its greater signal-to-noise ratio. For exemplars of turn-on LG@MOFs, see Appl. Mater. Today, 27, 101434 (2022), and ACS Sensors, 7, 2338 (2022).

(2) The location of encapsulated guest for LG@MOF systems has been unambiguously pinpointed by means of infrared nanospectroscopy (nanoFTIR) and nearfield imaging at a 10-nm spatial resolution. The pioneering work has been published in Nano Letters, 20, 7446−7454 (2020). Subsequently, we demonstrated the efficacy of nanoFTIR to probe the fine-scale structural distortions of MOF monoliths subject to mechanical deformation, see Mater. Today Nano 17, 100166 (2022). Another novel implementation of nanoFTIR was demonstrated in the context of acetone vapor sensing, upon VOC sorption and desorption, via in situ nanospectroscopy performed on a nanocrystal of MOF, see Adv. Mater. Interfaces 10, 2201401 (2023).

(3) Discovery of silver-based MOFs (termed OX-2) exhibiting a high quantum yield, excellent luminescent sensing capabilities and electroluminescent properties, the results have been published in Applied Materials Today, 21, 100817 (2020). OX-2 can be bulk synthesised in water under ambient conditions to easily yield 10-g scale materials. This exciting sensor material has been patented for future commercialisation by Oxford University Innovation.

Multistimuli optical sensors employing luminescent guest-MOF composites