A stock solution of the reaction mixture was prepared in DMF (dried over molecular sieve) based on previous reported literature with slight modification , specifically, by dissolving 2,5-dihydroxy-1,4-benzenedicarboxylic acid (DHBDC) (0.14 mmol, 27.1 mg) in 2 mL DMF, polyvinylpyrrolidone (PVP, MW=55 K) (250 mg) in 2 mL DMF, and CoCl2•6H2O (0.30 mmol, 71.4 mg) in 1 mL DMF separately, followed by sequentially mixing to obtain a 5 mL solution. 1 mL of the reaction mixture was withdrawn in a 4 mL glass vial for each reaction under conventional regular heating (using a RCT 5 digital IKA plate) or photothermal heating (using 520 nm or 660 nm LED, 8 W/cm 2 ) at 120 °C for 1-2 h. The product was isolated via centrifugation at 9000-10000 × g for 2 mins, washed with DMF and methanol at least 3-4 times, and finally dispersed in desired solvents (e.g., methanol, ethanol, DMF etc.) or dried in a vacuum for 1 h to get as powder form for further studies.