as 5 was activated by treating with piranha solution under previously used conditions. The surface was then PEGylated using 2 to give 6, the acetyl group of which was removed with ammonia to give 7. For solid phase synthesis, when the reaction site is close to the surface, the reaction is less efficient, therefore, the linker in 7 was elongated using compound 3. The elongation reactions were carried out on a MerMade 6 synthesizer under typical DNA synthesis conditions but with longer reaction time. After two cycles, 8 was given, which was converted to the target functionalized glass wool 1 under similar conditions on the synthesizer using compound 4 as the phosphoramidite monomer in the coupling step. More details for the synthesis are provided in the supporting information. The loading of the glass wool thus functionalized was determined to be 981 nmol/g (Entry 6, Table ) using a reported method, which is close to the calculated value 1,208 nmol/g (Entry 4).