Controlling hydrogenation selectivity with Pd catalysts on carbon nitrides functionalized silica

•S-C_T composites with different CNx loadings were prepared by changing the treatment temperature (T).•Pd catalysts with controlled particle size were prepared using S-C_T composites as support.•The Pd catalysts show high conversion and selectivity for a variety of hydrogenation reactions.•The Pd catalysts are stable in the COD hydrogenation reaction, even after reusing for 6 cycles.