1：Experimental Design and Method Selection:

The study involved selective etching of ScAl3C3 using tetramethyl ammonium hydroxide (TMAOH) to produce 2D ScCxOH, combined with density functional theory (DFT) calculations for structural and electronic analysis.

2：Sample Selection and Data Sources:

ScAl3C3 precursor was synthesized from Sc, Al, and graphite powders; etched samples were characterized using XRD, SEM, TEM, XPS, EELS, and photoresponse measurements.

3：List of Experimental Equipment and Materials:

Equipment included Pulsed Electric Current Sintering (PECS) apparatus, XRD (Bruker D8 Advance), FESEM (QUANTA 250 FEG), TEM (Tecnai F20), XPS (AXISUltra DLD), AFM (Dimension 3100V), EELS (FEI Titan3 60-300), and photolithography setup. Materials included Sc powders (99% purity, 100 mesh), Al powders (99% purity, 300 mesh), graphite powders (99% purity, 200 mesh), and TMAOH solution.

4：Experimental Procedures and Operational Workflow:

ScAl3C3 was synthesized via PECS, etched in TMAOH solution at 30-40°C for 72 hours, sonicated and centrifuged to delaminate flakes, and characterized. Photodetector devices were fabricated using photolithography and Ti/Au electrodes.

5：Data Analysis Methods:

Data were analyzed using Rietveld refinement for XRD, EDS for composition, XPS peak fitting, EELS for bandgap measurement, and I-V characteristics for photoresponse.