Non-lanthanide based NaBiF4 host have evoked remarkable interest due to unique luminescent property and potential applications. Current synthetic methods are not environment friendly and causes pollution. This is the first report mentioning green synthetic innovative route to develop upconversion, crystalline, and temperature sensing material. Here, we deigned ultrasonic assisted green approach for successful synthesis of β-NaBiF4:Yb³⁺, Er³⁺ (size ~25–100 nm) using Tabernaemontana divaricata leaves extract without any surfactant. Characterization techniques such as XRD, SEM, TEM, XPS, EDX, and PL unveiled its properties. Green and red upcon-version emissions (λ_ex = 980 nm) were two-photon absorption process. The possible energy transfer and thermal quenching mechanism is discussed. Using thermally coupled levels (²H_11/2 and ⁴S_3/2) of Er³⁺, FIR based tem-perature sensing revealed ΔE ~841 cm^-1, linear response (R² ~0.99), outstanding relative sensitivity (S_{r max} ∼ 1.4 % K^-1 @294 K), good absolute sensitivity (S_{a max} ∼ 0.29 %K^-1 @ 398 K) and a low temperature resolution (δT_min = 0.35 K) over temperature range 294–398 K.