2nd order Sallen-Key Bandpass filter design in Matlab
Your formulas do not take into account that the impedance of a capacitor is complex !

What you use is:

$$Zc(f) = 1 / 2 \pi f$$

but what you should use is:

$$Zc(s) = 1 / s$$

where $$s = 2 \pi f j $$  where j makes it imaginary remember: $$j^2 = -1$$

Have a look at this page on Wikipedia
where they show how to determine the transfer function in the s domain.