The extremely low lower passband frequency may make the bandpass filter design unrealisable. The best you may be able to hope for is to cascade a highpass and lowpass filter:
Coffs1 = fir1(1000,1/750,'high');
Coffs2 = fir1(100, 4/15, 'low');
x = [zeros(1,15000) 1 zeros(1,15000)];
y1 = filtfilt(Coffs1,1,x);
y2 = filtfilt(Coffs2,1,y1);
h = fft(y2)./fft(x);
Fn = 1/2;
Fv = linspace(0,1,length(h)/2-1);
Iv = 1:length(Fv);
figure(1)
subplot(2,1,1)
semilogx(Fv, 20*log10(abs(h(Iv))))
grid
ylabel('Magnitude (dB)')
subplot(2,1,2)
semilogx(Fv, angle(h(Iv))*180/pi)
grid
ylabel('Phase (degrees)')
xlabel('Normalised Frequency')
Experiment with these to get the response you want. This is my best effort!
