Which president in office borrowed money from China first?

The US does not specifically borrow from China. What happens is that after approval by Congress, the Treasury Department offers bonds for sale and foreigners are allowed to buy them if they wish. They are sold at auction. The president has nothing to do with who buys the bonds. Bonds can also be resold and transferred to new owners. Therefore, it is hard to know who owns them or when the first Chinese national bought a US bond. However, it is known that until 1972 or so, foreigners owned less that 5% of US treasury bonds, so Nixon would be a reasonable guess as the first president who started "borrowing" from China.