Multipoint plasmonic–MOF fiber sensor for CO2 monitoring in humid environments

Optical sensing using metal–organic frameworks (MOFs) have the potential to revolutionize environmental gas monitoring but remains constrained by single-point architectures and the lack of quantitative analysis of critical interferents such as humidity. Here, we overcome these limitations by fabricating a multi-point, multifunctional plasmonic–MOF sensor on a single optical fiber. Three plasmonic–MOF functionalized regions (Ag/MOF, Au/MOF, and MOF) were utilized to generate spectrally separated wavelength resonances at 573 nm, 611 nm, and 757 nm. These material-specific resonance signatures enable direct wavelength to location mapping, allowing spatially resolved CO₂ detection along a single fiber. Because all three regions use the same Cu–BTC sensing layer, the multiplexed architecture does not independently discriminate humidity from CO₂. Instead, the humidity influence is quantified using complementary transmittance and full width half maximum (FWHM) calibration models when relative humidity is independently measured. The multipoint three-region sensor exhibited a system-level response time of approximately 1 min and a limit of detection of 4000 ppm, whereas the single-point MOF sensor responded in approximately 10 s. We successfully developed a numerical model using a transfer-matrix method to simulate the CO 2 sensing performance with < 2% deviation. The present device is therefore a proof-of-concept platform for multipoint monitoring of CO 2 leakage from pipelines, carbon capture and storage (CCS) sites, and other infrastructures.